Home » Public Forums » GMCnet » Seeking advice. Engine failure. Non-GMC
| Seeking advice. Engine failure. Non-GMC [message #352236] |
Mon, 17 February 2020 23:28  |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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With so many people on this forum having experience in engine rebuilding I thought I may be able to find some answers.
I recently experienced a severe set back with my daily driver. One cylinders had failed in a spectacular way - a piece broke off along the edge above the top compression ring. I'm trying to figure out what may have caused the failure and I'm not having any luck so far.
The engine is a Mitsubishi V6 (6G74 version) from an SUV with 250k miles on it. I owned the vehicle since we bought it new. It was always maintained on schedule, never overheated, never ran out of oil. All parts (except few external things) are still OEM from assembly in Japan. The failure occurred at highway speed when I was passing another car. The engine started to shudder hard and check engine light came on. I stopped and pulled the codes - misfire on #5 cylinder (the one that failed). After some testing I determined that there was no compression on the said cylinder and the leak was going through the piston and into crankcase. Timing was on the spot correct, so no issue with the timing belt causing it.
I pulled the engine and found out that #5 piston had a hole in it. Pistons #1-4 have no wear marks at all, just normal discoloration from use. Cylinder walls on #1-4 still show good crosshatch marks. The failure of the #5 resulted in some scoring of the cylinder wall and aluminum deposits on the bottom of the head, but not much else. It seem that the failure occurred after some abnormal wear on the piston. Surprisingly to me, the #6 piston is showing what I presume an early stage of similar wear pattern to the #5. The wear pattern on #6 piston is very strange. The is no wear at all on the piston skirt (where you'd expect it most), but instead there are score marks on four sides of the piston at about 45 degrees from the piston pin. Rings are not stuck on pistons #1-4 and on #6. On #5 the rings are stuck due to damage. None of the pins are sticking (not even on th3 #5), the main bearings are within spec and show just normal and very even wear pattern on all four mains. Same goes for all the connecting rod bearings - good even wear, no scoring, no binding. Connecting rods on affected cylinders are not bent.
So the question is - does anyone know what may have caused such weird wear pattern on the affected pistons and what could cause piston to fail in such way?
Appreciate all of your input on this issue.
I'm going to try to attach links to photos. I hope it works.
Piston failure, top view, bank 1:
https://photos.app.goo.gl/FcmgXyMKJEDETsZ97
#5 failed piston, damage side view:
https://photos.app.goo.gl/kQCn1FXLwz67feYy6
#6 piston, no wear on skirt:
https://photos.app.goo.gl/k9L9pkG9JbdEdS5z7
#6 piston wear marks on 45 degree to pin:
https://photos.app.goo.gl/r7HG6FXXVj7v9Mnx7
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
[Updated on: Wed, 19 February 2020 12:43] Report message to a moderator |
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| Re: [GMCnet] Seeking advice. Engine failure. Non-GMC [message #352237 is a reply to message #352236] |
Mon, 17 February 2020 23:35  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Sounds like preignition or lean injector partially plunged.
Look at the plug from that cylinder.
Typical issue as it sneaked by all the emission computer warning.
On Mon, Feb 17, 2020 at 9:29 PM Vadim Jitkov via Gmclist <
gmclist@list.gmcnet.org> wrote:
> With so many people on this forum having experience in engine rebuilding I
> thought I may be able to find some answers.
>
> I recently experienced a severe set back with my daily driver. One
> cylinders had failed in a spectacular way - a piece broke off along the
> edge above
> the top compression ring. I'm trying to figure out what may have caused
> the failure and I'm not having any luck so far.
>
> The engine is a Mitsubishi V6 (6G74 version) from an SUV with 250k miles
> on it. I owned the vehicle since we bought it new. It was always
> maintained
> on schedule, never overheated, never ran out of oil. All parts (except few
> external things) are still OEM from assembly in Japan. The failure
> occurred at highway speed when I was passing another car. The engine
> started to shudder hard and check engine light came on. I stopped and
> pulled the
> codes - misfire on #5 cylinder (the one that failed). After some testing
> I determined that there was no compression on the said cylinder and the
> leak was going through the piston and into crankcase. Timing was on the
> spot correct, so no issue with the timing belt causing it.
>
> I pulled the engine and found out that #5 piston had a hole in it.
> Pistons #1-4 have no wear marks at all, just normal discoloration from use.
> Cylinder walls on #1-4 still show good crosshatch marks. The failure of
> the #5 resulted in some scoring of the cylinder wall and aluminum deposits
> on
> the bottom of the head, but not much else. It seem that the failure
> occurred after some abnormal wear on the piston. Surprisingly to me, the #6
> piston is showing what I presume an early stage of similar wear pattern to
> the #5. The wear pattern on #6 piston is very strange. The is no wear at
> all on the piston skirt (where you'd expect it most), but instead there
> are score marks on four sides of the piston at about 45 degrees from the
> piston pin. Rings are not stuck on pistons #1-4 and on #6. On #5 the rings
> are stuck due to damage. None of the pins are sticking (not even on th3
> #5), the main bearings are within spec and show just normal and very even
> wear pattern on all four mains. Same goes for all the connecting rod
> bearings - good even wear, no scoring, no binding. Connecting rods on
> affected cylinders are not bent.
>
> So the question is - does anyone know what may have caused such weird wear
> pattern on the affected pistons and what could cause piston to fail in such
> way?
> Appreciate all of your input on this issue.
>
> I'm going to try to attach links to photos. I hope it works.
>
> Piston failure, top view, bank 1:
> https://photos.app.goo.gl/FcmgXyMKJEDETsZ97
>
> #5 failed piston, damage side view:
> https://photos.app.goo.gl/kQCn1FXLwz67feYy6
>
> #6 piston, no wear on skirt:
> https://photos.app.goo.gl/k9L9pkG9JbdEdS5z7
>
> #6 piston wear marks on 45 degree to pin:
> https://photos.app.goo.gl/k9L9pkG9JbdEdS5z7
>
> --
> Vadim Jitkov
> '76 Glenbrook 26'
> Pullman, WA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmcrvparts.com
1-800-752-7502
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Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] Seeking advice. Engine failure. Non-GMC [message #352240 is a reply to message #352237] |
Tue, 18 February 2020 00:46 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Could be a very lean mixture, leading to elevated combustion temperatures,
and either preignition, which I suspect, or detonation, which would be the
least likely of these 2 events. Both create enormous combustion
irregularities, which easily can break parts like rings, ring lands,
abnormal flame fronts that burn holes in tops of pistons. Causes? Injectors
readily come to mind, as do intake manifold leaks, loose or faulty sensors,
obscure things like plug cross firing due to missrouted (crossed) secondary
wires. This wouldn't be the case in the event of coil pack secondary. You
stated that you were using heavy throttle at the moment of the failure.
This points to preignition as a likely suspect. Just my educated guess.
Like to have hands on that manifold, as well as the injectors,
filters, and fuel pump(s) and fuel pressure regulator. Broken parts are
symptoms, not cause agents. That is always what I look for. There will be
other opinions, these are mine.
Jim Hupy
Salem, Oregon
On Mon, Feb 17, 2020, 9:36 PM Jim Kanomata via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Sounds like preignition or lean injector partially plunged.
> Look at the plug from that cylinder.
> Typical issue as it sneaked by all the emission computer warning.
>
> On Mon, Feb 17, 2020 at 9:29 PM Vadim Jitkov via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> With so many people on this forum having experience in engine rebuilding
> I
>> thought I may be able to find some answers.
>>
>> I recently experienced a severe set back with my daily driver. One
>> cylinders had failed in a spectacular way - a piece broke off along the
>> edge above
>> the top compression ring. I'm trying to figure out what may have caused
>> the failure and I'm not having any luck so far.
>>
>> The engine is a Mitsubishi V6 (6G74 version) from an SUV with 250k miles
>> on it. I owned the vehicle since we bought it new. It was always
>> maintained
>> on schedule, never overheated, never ran out of oil. All parts (except
> few
>> external things) are still OEM from assembly in Japan. The failure
>> occurred at highway speed when I was passing another car. The engine
>> started to shudder hard and check engine light came on. I stopped and
>> pulled the
>> codes - misfire on #5 cylinder (the one that failed). After some
> testing
>> I determined that there was no compression on the said cylinder and the
>> leak was going through the piston and into crankcase. Timing was on the
>> spot correct, so no issue with the timing belt causing it.
>>
>> I pulled the engine and found out that #5 piston had a hole in it.
>> Pistons #1-4 have no wear marks at all, just normal discoloration from
> use.
>> Cylinder walls on #1-4 still show good crosshatch marks. The failure of
>> the #5 resulted in some scoring of the cylinder wall and aluminum
> deposits
>> on
>> the bottom of the head, but not much else. It seem that the failure
>> occurred after some abnormal wear on the piston. Surprisingly to me,
> the #6
>> piston is showing what I presume an early stage of similar wear pattern
> to
>> the #5. The wear pattern on #6 piston is very strange. The is no wear
> at
>> all on the piston skirt (where you'd expect it most), but instead there
>> are score marks on four sides of the piston at about 45 degrees from the
>> piston pin. Rings are not stuck on pistons #1-4 and on #6. On #5 the
> rings
>> are stuck due to damage. None of the pins are sticking (not even on th3
>> #5), the main bearings are within spec and show just normal and very even
>> wear pattern on all four mains. Same goes for all the connecting rod
>> bearings - good even wear, no scoring, no binding. Connecting rods on
>> affected cylinders are not bent.
>>
>> So the question is - does anyone know what may have caused such weird
> wear
>> pattern on the affected pistons and what could cause piston to fail in
> such
>> way?
>> Appreciate all of your input on this issue.
>>
>> I'm going to try to attach links to photos. I hope it works.
>>
>> Piston failure, top view, bank 1:
>> https://photos.app.goo.gl/FcmgXyMKJEDETsZ97
>>
>> #5 failed piston, damage side view:
>> https://photos.app.goo.gl/kQCn1FXLwz67feYy6
>>
>> #6 piston, no wear on skirt:
>> https://photos.app.goo.gl/k9L9pkG9JbdEdS5z7
>>
>> #6 piston wear marks on 45 degree to pin:
>> https://photos.app.goo.gl/k9L9pkG9JbdEdS5z7
>>
>> --
>> Vadim Jitkov
>> '76 Glenbrook 26'
>> Pullman, WA
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> --
> Jim Kanomata
> Applied/GMC, Newark,CA
> jimk@appliedairfilters.com
> http://www.appliedgmcrvparts.com
> 1-800-752-7502
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: Seeking advice. Engine failure. Non-GMC [message #352242 is a reply to message #352236] |
Tue, 18 February 2020 08:03 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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I'm in agreement with Jim and James. Could be long term light/ med undetected pinging that slowly eroded the metal. Then failed during passing. An alternative theory is a slack timing belt causing retarded events and high temps due to poor efficiency.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Seeking advice. Engine failure. Non-GMC [message #352248 is a reply to message #352236] |
Tue, 18 February 2020 11:21 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I'd buy running lean on those two - the timing belt would affect either everything or everything on one bank, would it not? Although 250K ain't a bad ride, you got your money out of it. One other possibility, I'm not aware of the ignition system, but is it possible those two cylinders fire off the same winding of the coil pack? If so, I'd go looking for a problem with that winding or its firing mechanism. A worn or broken prong on the distributor reluctor?
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Seeking advice. Engine failure. Non-GMC [message #352249 is a reply to message #352236] |
Tue, 18 February 2020 12:36 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Great input. Thank you to all for taking time with it.
The lean condition sounds like the most plausible scenario. I'm going to take injectors and get them flow tested. If #5 and #6 show significantly lower output than the other four, it will confirm this theory.
What does a plug look like on a very lean mixture? #5 spark plug was covered in oil due to the forced ventilation with the crankcase. But I can check to see if #6 plug is somewhat different from first four.
Would elevated combustion temperatures cause the pistons to expand unevenly and rub on the cylinder walls in such strange way?
I'm pretty confident that we can rule out the timing belt. It is an interference engine and having timing belt off the mark would result in valve damage first. Additionally, when I pulled the engine, timing on both banks was perfectly on the mark. No slack on the belt and tensioner was in spec with proper preload.
The engine has three individual ignition coils that are electronically controlled. They are paired to fire as 5+2, 1+4 and 3+6 (waste spark system). Thus, this puzzle piece does not fit ether.
Someone on another forum suggested a possibility of a restriction in the oil gallery and thus reduced lubrication on the last two cylinders. Does that sound like a plausible idea? If that were the case, I would expect a heavier wear/damage on the main bearings near those two cylinders or at the very least on the rod bearings. Alas, they all looked evenly worn and without damage.
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
[Updated on: Tue, 18 February 2020 12:37] Report message to a moderator |
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| Re: Seeking advice. Engine failure. Non-GMC [message #352250 is a reply to message #352249] |
Tue, 18 February 2020 14:18 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Ready Vadim?
If you have been reading here much, you might remember that I am a refugee from the laboratories in Detroit that do engine testing. I have seen this type of damage before and will try to make the possible causes clear. If I loose you somewhere along the way, please say so and I will try to correct the issue. Great pictures - by the way.
I started writing this about three hours ago, but I had to break off. That is why there are some things answered since that I also answered. Too much information don't hurt.
Hold on tight because here we go....
What actually caused the damage to #5 piston will be hard to determine, but suffice it to say that it probably happened in a fractional second. Even a grocery-getter engine is running with very little margin. Yours just slipped the margin.
The picture of the piston crown is typical of a pre-ignition issue. There are so many possible causes. That (again with the hands on thing) that I cannot get more specific with out much closer examination. With the damage to the piston as it is there are several choices:
My first would be (because it is simplest) that the ignition timing to that cylinder was wrong. If this is a distributor engine, that is easy to do just by getting wires too close together.
It is also a rear cylinder and they often are less well cooled at the cylinder liner. (Yours are parent metal, but that makes little difference.) At full power, cylinder cooling is critical. If it was a loss of cooling jacket capability, that would also explain what happen to #6 piston. (More below) Part of this question could be indicated by the condition of the cylinder heads. If the individual cylinder combustion chambers show variation in operating temperature, you may have has a cooling jacket issue that you did not suspect.
That cooling could also be a failure of the piston cooling. Pistons are cooled by both the contact with the cylinder liner and by the lubricating oil that is delivered from below. Without having been inside this engine. (I did run one for a supplier, but it ran out the durability and went home intact.) I do not know if this oil delivery was common to both 5 & 6.
The pre-ignition issue need not be spark induced. These engines are relatively high compression. This can cause an interesting problem where the shock wave of the spark ignition causes a detonation somewhere removed in the combustion chamber. The edges of the piston crown seen to be the usual first choice because that is a hot area. Once it gets started, even my engines that were "by individual cycle" monitored, could not unload and shut down fast enough to avoid extending the damage.
If this is one of the direct injection engines, then I would start thinking in terms of a lean cylinder. (Did you know that aircraft people used to refer to automotive engines as being "gasoline cooled". But they have their own issues.) Even port injection can have similar issues, just seldom as bad or as fast.
Once that top land was gone, the top ring could not hold the fire load and when the fire went by it quickly took out the metal below. So that damage is what I would expect. The heat on the cross head (thrust face) of the damaged piston is an artifact of the overheat of the piston. This is part of why big engine pistons are actually two or three separate parts with the crown and ring carrier isolated from the skirt/crosshead.
About that #6 piston. The reason that those areas are scuffed is probably that this piston was overheated as well. If you think of the piston as being two parts. Then the fact that the skirt/crosshead got hotter than would fit in the bore should be making some sense. The actual thrust face of a cast piston is flexible, but the wrist pin carrier and crown cannot be. So, when the piston got too big, those areas got jammed against the liner/bore face and broke down the lubrication and cooling there. Why didn't this happen to the crown/ring carrier? Because that is smaller diameter. Pistons are not mathematical cylinders by any means.
Now, What to do about this?
Assuming you choose to recover this engine and not just replace it.
You say the other essential parts show no distress. Correct??
It appears that there is very little top ring travel step. A finger tip can detect about 0.001. If it is more than that, you have to measure it to know where you are going next.
Do not let anybody bore all the holes to the same size. There is no reason to do this. Find a piston supplier that can and will supply single pistons. Get their standard sizes that they supply. If you do a fast try to clean that bore with a glaze breaking hone, and when you have gotten it pretty clean, you can't catch a finger nail in it, just get two new standard pistons. If that fails , then get block power honed NOT BORED to the first size that cleans the scoring. If this is less than 0.002" larger than specified, you can probably get by with a standard sized piston. But get piston sizes before you do anything else.
A lot of production and less careful shops will just bore everything 30 over. Then that engine is done. I have one of those and it really pissed me off to find that I had a 461 instead of a 455.
You may need to match piston weights, but this is a simple operation - unless you need to remove a lot of metal.
There is no reason that this engine can't be returned to service and be as good as it ever was. If you do it, it is all just a question of attention to detail.
Oh, If you don't have a good engine work stand, just go buy one. You will be spending a lot of time next to it.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Seeking advice. Engine failure. Non-GMC [message #352270 is a reply to message #352236] |
Wed, 19 February 2020 07:45 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Interesting analysis. Makes you wonder if the fuel rail picked up a piece of crud, too.
Aviation flat motors are gasoline cooled at take off power - the carburetors open a 'power valve' whose function is to richer the mixture substantially and let the excess fuel evaporation cool the piston and (hopefully) preclude detonation. Actually in operation, the aviation engine is much closer to the marine engine than to an automobile engine. Both are designed to run at pretty much a constant speed and constant load. The aviation engine, however values low weight over specific output, so we see outputs on the order of half or three quarters HP per cubic inch displacement. Avco Lycoming made the biggest flat motor I ever messed with, a 720 CID unit which produced 400 HP. We see auto engines which peak at 700 HP or better at what - right below 400 CID, although these and most car engines probably wouldn't sustain that output over long periods of time.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Seeking advice. Engine failure. Non-GMC [message #352273 is a reply to message #352270] |
Wed, 19 February 2020 08:19 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Johnny Bridges wrote on Wed, 19 February 2020 08:45Interesting analysis. Makes you wonder if the fuel rail picked up a piece of crud, too.
Aviation flat motors are gasoline cooled at take off power - the carburetors open a 'power valve' whose function is to richer the mixture substantially and let the excess fuel evaporation cool the piston and (hopefully) preclude detonation. Actually in operation, the aviation engine is much closer to the marine engine than to an automobile engine. Both are designed to run at pretty much a constant speed and constant load. The aviation engine, however values low weight over specific output, so we see outputs on the order of half or three quarters HP per cubic inch displacement. Avco Lycoming made the biggest flat motor I ever messed with, a 720 CID unit which produced 400 HP. We see auto engines which peak at 700 HP or better at what - right below 400 CID, although these and most car engines probably wouldn't sustain that output over long periods of time.
--johnny
Johnny,
While that is all very true, only aircraft fall out of the sky if the motor quits. For most others, this is just an inconvenience.
Matt - BTDT with all three
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Seeking advice. Engine failure. Non-GMC [message #352277 is a reply to message #352236] |
Wed, 19 February 2020 12:31 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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True dat. If we took the time we take looking at the airplane to look at our ground based rides, we'd have less stops beside the road.And if we took the same time teaching drivers as we do flyers, it's my contention we'd have a lot fewer road crashes as well. <400 people offed in 737MAX airplanes, they're grounded and nobody will fly in one. 40 some thousand offed on the roads. Yawn.
Crichton was right.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Seeking advice. Engine failure. Non-GMC [message #352284 is a reply to message #352277] |
Wed, 19 February 2020 16:52 |
dsmithy
Messages: 210
Registered: July 2012
Location: Lincoln Nebraska
Karma: 0
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Some say the eyes are the windows to the soul. I submit it’s also an engine discussion.
Vadim gets the benefit of the hard info, the rest of us get a great ride to labs and other places we’ll likely never get to go. Well done, gentlemen.
Douglas & Virginia Smith
dsmithy18 at gmail
Lincoln Nebraska
’73 “Canyonlands” since ‘95: “Wanabizo”, Anishinabe Indian for “He gets lost driving” Yes, really.
Quadrabag/6 wheel disks/3;70 final/Paterson QuadraJet/Thorley’s/Sundry other
P&W PT6, no wait, that's the wish list...
> On Feb 19, 2020, at 12:31 PM, Johnny Bridges via Gmclist wrote:
>
> True dat. If we took the time we take looking at the airplane to look at our ground based rides, we'd have less stops beside the road.And if we took
> the same time teaching drivers as we do flyers, it's my contention we'd have a lot fewer road crashes as well. they're grounded and nobody will fly in one. 40 some thousand offed on the roads. Yawn.
>
> Crichton was right.
>
> --johnny
> --
> Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
> Braselton, Ga.
> I forgive them all, save those who hurt the dogs. They must answer to me in hell
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Douglas & Virginia Smith,
dsmithy18 at gmail,
Lincoln Nebraska,
’73 “Sequoia” since ‘95: "Wanabizo";
Quadrabag/6 wheel disks/3:70 final/Paterson QuadraJet/Thorley’s/Alloy wheels/Sundry other
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| Re: Seeking advice. Engine failure. Non-GMC [message #352292 is a reply to message #352236] |
Thu, 20 February 2020 00:14 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Senior Member |
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What never ceases to amaze me on this forum is how the discussion threads morph and wonder off into all sorts of interesting directions, while at the same time seamlessly providing deep dives into the main subject of discussion. My guess it happens because as we start pulling on one memory thread, lots of other interconnecting things come with it. I laughed as soon as I saw the thread move to discussion of airplane engines vs. ground vehicle engines. I can't even imagine what its like to sit down for a coffee of beer with you folks. Oh the places we'll go... 
Matt - thank you for the detailed write up. Everything you say makes sense and I think I get all of it. You are 100% right - the failure happened in a microsecond. As I said earlier, I was passing the car and suddenly engine made the most awful rattle and I felt the biggest misfire I've ever experienced in any vehicle. The abnormality was big enough that I pulled over immediately after passing the car (I'm sure to the curses from the other driver) and just as the CEL came on at the same time.
I've never thought of pistons as being manufactured from different materials, but now that I think about it, it makes perfect sense. You need stiffness and strength around the pin, heat resistance on thrust face and slipperiness and wear resistance on the skirt area. Why is this not a common knowledge for anyone who is not an engineer?
The engine is port injected with individually controlled injectors. As far as I understand they fire one at a time on intake stroke for each piston.
There is one thing I don't fully understand. You said: "It is also a rear cylinder and they often are less well cooled at the cylinder liner. (Yours are parent metal, but that makes little difference.)" What does it mean "parent metal"? I've never came across that term before.
There is no restrictions in the water jacket in the case or in the head. I've looked all around the cylinder jackets in the case and all water passages appear to be clean and unrestricted without any rust of calcium build up. Same goes for the heads. The theory of unintentional very lean condition seem to be most plausible. I will definitely check the injectors for flow rates.
As far as the future of the engine, my plan is to fix it and put it back in service. I'm one of those stubborn people going for the record on this vehicle. I got 250k miles on it (all of them are mine). As far as I know it is just past the distance to the moon. My plan is to "turn around" and make it back... Ha ha, its time for the NASA folks to join the conversation I've checked the ring step - there is absolutely none present on any of the cylinders. The only thing I can feel with my fingernail is one of the two bigger vertical scratches on the #5 bore. All bearings are in amazing condition with oil gaps safely in the middle of the "Standard value" range for this engine and far far smaller than indicated wear limit value (this is according to the Factory Service Manual). With that I think it might be best to leave all the bearings as they are. What do you think?
I finally was able to get hold of a good reputable machine shop not far from here. I explained to the owner what I'm dealing with and he said he can recondition cylinders and get the right pistons ordered. I'm going to take all the parts (crank case, pistons, heads, etc.) to him tomorrow, so that we can look at them together and confirm our plan of action. I plan on printing Matts instructions, so that I don't miss something when talking to him. I think I'll have him clean up the heads too while we at this point. Sounds like I can do the reassembly myself, which is going to be fun and I'm looking forward to it. It is truly surprising how much more space an engine takes when it is disassembled...
BTW, I took pictures of the combustion chambers on the heads for all pistons. I don't know if that will tell you anything, but the links are posted below. I grouped them by order for each bank. You can see where piston material from #5 got deposited on the bottom of the head. It had completely pulverized that piston fragment.
Again thank you all for the input. I love this kind of classroom
Combustion chamber:
#1 https://photos.app.goo.gl/pFKathc2H9zTrR796
#3 https://photos.app.goo.gl/VbQnrqVPLGx2GQfK6
#5 https://photos.app.goo.gl/8VtDKRYerEdk4CMf8
#2 https://photos.app.goo.gl/vVnkkN4Pkph6T2ZXA
#4 https://photos.app.goo.gl/vkgcqE3RGbeyfKQ76
#6 https://photos.app.goo.gl/qRmK5aEApzgyTXQK9
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: Seeking advice. Engine failure. Non-GMC [message #352298 is a reply to message #352292] |
Thu, 20 February 2020 09:28 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Senior Member |
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Certainly ask your machinist about this, but it would make sense, to me anyway, to at least polish the crankshaft and install new standard size bearing shells.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
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| Re: Seeking advice. Engine failure. Non-GMC [message #352300 is a reply to message #352236] |
Thu, 20 February 2020 10:39 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Vadim,
The reference to parent metal is just habit. Most of the engines I have run had cylinder liners that were not the same material as the cylinder block and crankcase. This has both advantages and disadvantages, but I will not go down that list right now.
And, Oh Yes, most pistons in modern engines have inserts in the castings to improve the structure where it is needed. This is not new and it is why scrap pistons have a much lower value than if they were clean aluminum. Multi-part pistons actually start at a smaller bore than you might expect. Commercial diesels at that way from only a 4" bore. But then again diesels tend to be brutal about their pistons.
What I do want to point out to you right now is that the condition of the intake valves of both #5&6 is different than the rest. This means something was different. It may just be cooling, but I don't think so. Both of the rear cylinder's valves are different that the other four. Now, one of the things you have to crank into the evaluation is that with virtually all V-pattern engines coolant flow is down the block and back the head. Then it is up to the engineers to put the correct holes in the gasket so as to control the flow in that area so things get enough cooling.
You say that you did not see anything in the cooling jacket during disassembly, we what ever it was may have left by then. Carefully inspect both gaskets. You may not be able to see the witness marks but that still is a possibility.
Since you have found a good shop, have him re-seat the valves. He can also blast those and then heads clean and you may have an engine that runs better than new when you are done.
As to assembly, if you print the pages and check off the steps, you will be less likely to make a mistake. Do not be too proud to take something apart because you did not check that step. If you really don't mind being kind of anal about the whole job, do a full build book. (I have always done this because I had a good mentor.) That really will end up being two different files (spreadsheets are good for this) one of those should be the supplier and part numbers of everything you had to buy to do the assembly. The other should contain all the measurements of the components and thereby it can also include the clearances of related parts. (Gee, you have that all in the spreadsheet, just have it do the math.)
While you are at it all, record the combustion chamber volume, the piston relief or protrusion as the clearance volume in the bore and the gasket thickness and bore. This way you will have a real record of the compression ratio. You may have to contact the cylinder head gasket supplier for the design compressed thickness of the part.
With all that, if you have questions or doubts (or just want to bounce something off me) I am in the Black's list. If you ring my home phone, that is a better bet as the cell is unreliable at home. I read that @ddress all the time as it comes to my phone and my desk.
I wish you an effective effort. I as you can guess, I have been at this a while but it never gets old. The pride you can hold when you get it beck running will be real. (My most recent was the 455/461 in my coach. It broke a piston, and I did every that I could do my self. This was engine 23 and I don't count engines I can carry.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Seeking advice. Engine failure. Non-GMC [message #352301 is a reply to message #352298] |
Thu, 20 February 2020 10:34 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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If your going to have it torn apart, I suggest it would be beneficial to
have other things done.
Valve guides are possibly worn, etc
On Thu, Feb 20, 2020 at 7:28 AM Carl Stouffer via Gmclist <
gmclist@list.gmcnet.org> wrote:
> Certainly ask your machinist about this, but it would make sense, to me
> anyway, to at least polish the crankshaft and install new standard size
> bearing shells.
> --
> Carl Stouffer
> '75 ex Palm Beach
> Tucson, AZ.
> Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive,
> Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American
> Eagles,
> Solar battery charging. GMCSJ and GMCMI member
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Seeking advice. Engine failure. Non-GMC [message #352305 is a reply to message #352236] |
Thu, 20 February 2020 13:15 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Senior Member |
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Just returned from the mechanic's shop. His first words were - that crankcase doesn't look bad at all. After looking at the busted piston, he confirmed your suspicion of lean condition and detonation that took out #5 piston. He said his will re-hone all bores. He is pretty sure that #6 cylinder will clean out just fine without any other work, but he'll have to check #5 after honing it to see if all scratches come out. I emphasized that I wanted to avoid boring it out as much as possible. He will get back to me after cleaning everything and trying to machine hone it. He agreed that the main bearings were in good condition and he did not want to replace them. Crankshaft checked out good too. He will polish the bearing surfaces but no other work needed there. He suggested that we replace rod bearings, since, as he put it, they take more hard beating relative to main bearings. I think I'm OK with that. He will also check the compression ring seat clearances and that will determine if we will go with all new pistons or just two.
I agree with Matt's observation of the heads. It definitely confirms the different running conditions on 5 and 6. I'll take a close look at the head gaskets.
As far as being anal during the assembly, I'd wager I'm on the far end of the Normal distribution curve right next to the OCD level I feel good about it. I got the detailed book and all tightening specifications and torque sequences. I'm looking forward to get at it.
Couple questions that you might help me with - during assembly, when assembling the bearings, do you need to lubricate back side of the bearing (against the rod), or just the bearing surface that will be in contact with the crank case? 2. What is a good break in procedure after rebuild. There is too many different ways of doing it and many contradict the others. Manual calls for 5x30 grade of engine oil, and that is all that engine ever had. Any special oil for break in period? How soon to change it out?
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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| Re: Seeking advice. Engine failure. Non-GMC [message #352306 is a reply to message #352305] |
Thu, 20 February 2020 15:50 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Senior Member |
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NextGenGMC wrote on Thu, 20 February 2020 13:15
Couple questions that you might help me with What is a good break in procedure after rebuild. There is too many different ways of doing it and many contradict the others. Manual calls for 5x30 grade of engine oil, and that is all that engine ever had. Any special oil for break in period? How soon to change it out?
I have a little different philosophy/opinion about break-in. IMO, if machining and cylinder preparation is done correctly with modern day equipment, break-in occurs for the most part in the first several hundred to 1K miles. I also believe that it is not only not necessary, but a mistake to use "Break-in oil" to break-in a new/rebuilt engine. Break-in oils are supposed to be formulated to allow parts to 'wear-in" to each other...in other words allow some wear to take place. Why would you want to do that to new bearings? Some wear must take place on the cylinder walls for rings to seat and seal properly. So, how does oil select the parts that it allows to wear. It can't. If you look at a freshly honed cylinder wall under a microscope, the hone leaves scratches...peaks and valleys. Break-in is the rings just knocking the peaks off, metal that is filtered out by the oil filter and comes out in the first oil change which I believe should take place in the first 100 miles. It does not take a special oil to allow peaks to get knocked off, so IMO use whatever oil you plan to run in the engine be it Dino or Synthetic. Change after the first 20 minutes of lifter/cam break-in, (oil and filter) and again at 100mi, 500mi, and 1000 miles. Then go to your normal oil change intervals. During this break-in period I think it is important to place a "Filter Mag" on the filter to magnetically catch as much break-in metal as possible. The last engine I built was my Cad 500. I broke it in with 0W40 Mobile 1. I did NOT use any ZDDP additives. I just ran from NW Wisconsin to Jacksonville FL, about 1500 miles. The engine consumed 1/2pint over that 3 day period. This engine with now 24K miles, has never needed additional oil added between changes. To help with controlling oil consumption, I also did some things to rod and main bearings, valve guides, a special piston ring, and got control of the PCV system. I can elaborate on this if you wish.
In addition, I believe that with todays oil formulations, we should be using the synthetic multigrade oils. 5W30 allows good immediate flow to the bearing surfaces on morning starts while maintaining viscosity on hot runs. I personally use 0W40 Mobil 1 "FS" European Car Formula, ACEA A3/B3, A3/B4, API SN synthetic, or use 5W30 Quaker State Ultimate Durability, dexos 1 Gen 2, API SN "Plus", synthetic (green bottle) because of their wear protection capabilities. Both of these oils are available at Walmart for under $25 for a 5 qt pail. I like the "0W" weight for start-up in cold Wisconsin weather, and the "40W" for hot running. Has worked well for me. So, this is all JMHO based on my own personal experience. Take it for what it's worth.
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
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| Re: Seeking advice. Engine failure. Non-GMC [message #352308 is a reply to message #352236] |
Thu, 20 February 2020 17:34 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Mr. John specified breakin oil a particulaor one in fact, and said a couple or three hundred miles was plenty. One more run on the freeway when the rain quits, and I'll change it for regular.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: Seeking advice. Engine failure. Non-GMC [message #352309 is a reply to message #352236] |
Thu, 20 February 2020 18:13 |
NextGenGMC
Messages: 146
Registered: December 2017
Location: Washington State
Karma: -1
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Senior Member |
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Valid point. As far as I know you have to not keep the engine at constant RPM for too long during first couple hundred miles. I like the idea of the magnet on the oil filter. I cut open filters at oil changes and check how everything looks in there. Would be interesting to see what kind of goop magnet will attract out of the oil during the breaking oil change.
I ran 5x30 Quaker state oil on this engine. Had served me well so far.
Vadim Jitkov
'76 Glenbrook 26'
Pullman, WA
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