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| Re: Name that tune? GMC Engine noise [message #287499 is a reply to message #287476] |
Fri, 18 September 2015 10:55   |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Sloppy rod bearing. The sound is the piston hitting the ridge on the head. Hope that isn't it and the recording is not good but that's my guess.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Name that tune? GMC Engine noise [message #287502 is a reply to message #287476] |
Fri, 18 September 2015 11:20 |
Joe Weir
Messages: 769
Registered: February 2013
Location: Columbia, SC
Karma: 7
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Mine made that same "rattle-ly" noise before the rod started knocking loudly. It sounded like something was loose, as it changed with engine rpm as if it was a vibration generated noise, like something loose on the outside. It was not.
I hope that yours is a loose fuel pump.
76 Birchaven - "Wicked Mistress" - New engine, trans, alum radiator, brakes, Sully airbags, fuel lines, seats, adult beverage center... those Coachmen guys were really thinking about us second hand owners by including that beverage center...
Columbia, SC.
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| Re: Name that tune? GMC Engine noise [message #287519 is a reply to message #287476] |
Fri, 18 September 2015 16:09 |
Charles
Messages: 455
Registered: January 2004
Karma: 0
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Eugene,
How is your oil pressure?
What is your Engine temperature doing?
If these aren't bad I would drive it home slowly.
Bad rod bearing can go a long way if you don't push it.
I no longer have wrecker or flat bed hauler available.
Call your insurance and let them find someone. Insist
on heavy duty wrecker. Medium won't handle it. Watch
the radiator if you get a front wheel wrecker. Can you call me?
Charles
Charles Wersal
Duncanville, Texas
26 foot 1975 Glenbrook
Pandora's Box
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| Re: Name that tune? GMC Engine noise [message #287520 is a reply to message #287476] |
Fri, 18 September 2015 16:14 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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batman wrote on Thu, 17 September 2015 22:49On my way to far west Texas, started hearing a knocking noise.
Anyone want to make a guess as to what is wrong?
Here is a link to a video clip taken with my phone over the engine hatch.
https://youtu.be/rKsQrKE5eiw
It starts at around 1000rpm then settles down above 2500rpm.
I'm about 150 miles from home 
It sounds a bit random to be a rod knock but hard to tell.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Name that tune? GMC Engine noise [message #287543 is a reply to message #287476] |
Fri, 18 September 2015 21:36 |
Gadabout
Messages: 124
Registered: March 2013
Location: Edmonton
Karma: 2
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The sound file is good but without a direction reference it is hard to guess.
Rod bearings often start with a tick , then get louder ( like a hammer) just before the block gets a hole in it....
You can eliminate external components such as the water pump, alternator and AC compressor by removing the belts and starting the engine.
Faulty lifter or push rod can be checked by pulling the valve covers.
I just had a water pump go and it made a similar noise just before final detonation.
If you think its internal, chances are it won't make many more miles.
Good luck....
Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45
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| Re: Name that tune? GMC Engine noise [message #287547 is a reply to message #287543] |
Fri, 18 September 2015 23:14 |
LarryInSanDiego
Messages: 336
Registered: September 2006
Karma: 0
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If it's a specific cylinder, disconnect one spark plug wire at a time to identify it. The fact that the noise disappears has me doubting that it's a specific cylinder (rod knock, piston rocking, etc.).
Larry Engelbrecht
San Diego, CA
'73 26' ex-Glacier
TZE063V100319 03/07/73
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| Re: Name that tune? GMC Engine noise [message #287573 is a reply to message #287562] |
Sat, 19 September 2015 19:04 |
George Beckman
Messages: 1085
Registered: October 2008
Location: Colfax, CA
Karma: 11
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batman wrote on Sat, 19 September 2015 10:42Thanks for all the suggestions. I had the camper towed home, did not want to risk a catastrophic failure driving it any more. Now trying to narrow down the problem.
I disconnect each spark plug one at a time, and the knocking went away when I disconnected cylinder #5.
So does this narrow it down to a rod bearing problem on cylinder #5, or could it be something else?
Also, if it is a rod bearing. Is that a repair that can be done without pulling the engine? Drop the tranny and oil pan and get to it from the bottom?
Sorry to hear all this. If it is a rod, the engine has to come out and probably rebuilt. When rod bearings start to knock they break up and metal starts going everywhere. At least they will have to carefully check the crank shaft to make sure the knock did not beat it out of round.
This is the sound we all dread.
'74 Eleganza, SE, Howell + EBL
Best Wishes,
George
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| Re: Name that tune? GMC Engine noise [message #287575 is a reply to message #287573] |
Sat, 19 September 2015 19:12 |
LarryInSanDiego
Messages: 336
Registered: September 2006
Karma: 0
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If #5 rod bearing happens to look good, it's likely a collapsed piston skirt, allowing the piston to rock. Which COULD cause it to kiss the head, but squish clearance is often quite generous, so that's unlikely unless the deck had been previously machined and/or the mains line bored. A LOT.
I had a '71 455HO Trans Am with so much piston skirt wear, not to mention cylinders undoubtedly oval'ed from thrust wear, that you could visibly rock the piston with your thumbs when the heads were off. Which I did a lot seeing how I was frequently blowing head gaskets from getting greedy with nitrous oxide use.
But that one didn't make noticeable piston knock, at least with the no so quiet exhaust on that car. I did have an '83 BMW 528e with a piston knock with similar symptoms to yours - only within a certain rpm range and on a specific cylinder.
Fuel pump is worth checking out. The old school sbc fuel pump used a pushrod. For some reason, my '67 Nova 283 had one that alarmingly rattled. New fuel pump made it quiet again,, even with the existing pushrod, so maybe the old pump somehow limited arm retraction, or it was somehow bent. Just some possibilities to consider...
Larry Engelbrecht
San Diego, CA
'73 26' ex-Glacier
TZE063V100319 03/07/73
[Updated on: Sat, 19 September 2015 19:35] Report message to a moderator |
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| Re: Name that tune? GMC Engine noise [message #287576 is a reply to message #287575] |
Sat, 19 September 2015 19:22 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Bummer gene it looks like your only choice is to pull the engine don't see any other choice. I lost a thrust bearings in mine and still haven't got all the needed parts to put it back together.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Name that tune? GMC Engine noise [message #287579 is a reply to message #287562] |
Sat, 19 September 2015 19:54 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Eugene,
By disconnecting the spark plug you stopped the "explosion" that occurs when the fuel/air mixture ignites and reduced the load on
the wrist pin and rod bearings which stopped the noise. I would say that the problem is in cylinder 5. Most likely it is the rod
bearing, however, it could be something else. Cracked piston? Loose wrist pin? Broken Rings? Dunno.
To remove the oil pan you must:
1) Remove all the spark plugs so you can turn the engine over by hand
2) Remove the driver and passenger side final drive flange / inner CV joint bolts
3) Remove the final drive to gain access to the oil pan bolts on that side of the engine
4) Remove the oil pan bolts
5) Disconnect the mounts that connect the engine and transmission to the frame
6) Lift the engine far enough to allow the pan to clear number 1 main bearing
You now have access to the rods.
7) Rotate the engine so that the # 5 rod cap nuts can be accessed easily
8) Remove the number 5 rod bearing cap and inspect the bearing and crank
If you are lucky the crank won't be scored, however, quite frankly you would have to be VERY lucky!
Also it is quite possible that the other bearings may also be on their way out and they too should be inspected.
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: eugene
Thanks for all the suggestions. I had the camper towed home, did not want to risk a catastrophic failure driving it any more. Now
trying to narrow down the problem.
I disconnect each spark plug one at a time, and the knocking went away when I disconnected cylinder #5.
So does this narrow it down to a rod bearing problem on cylinder #5, or could it be something else?
Also, if it is a rod bearing. Is that a repair that can be done without pulling the engine? Drop the tranny and oil pan and get to
it from the bottom?
--
eugene
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Name that tune? GMC Engine noise [message #287581 is a reply to message #287579] |
Sat, 19 September 2015 20:21 |
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batman
Messages: 100
Registered: January 2004
Location: Benbrook, TX
Karma: -3
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Senior Member |
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Rob,
On #5, do both the front mounts and the rear mounts need to be disconnected? Or can just the front mount be disconnected, the rears mount loosened, and the front of the engine lifted? Any guess as to how much lift is needed for the pan to clear?
USAussie wrote on Sat, 19 September 2015 19:54Eugene,
<...snip...>
5) Disconnect the mounts that connect the engine and transmission to the frame
6) Lift the engine far enough to allow the pan to clear number 1 main bearing
<...snip...>
eugene
benbrook, tx
77 Eleganza II, Howell EFI + EBL
http://gmc.backyardwildlife.com
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| Re: [GMCnet] Name that tune? GMC Engine noise [message #287583 is a reply to message #287581] |
Sat, 19 September 2015 20:37 |
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USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
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Senior Member |
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Eugene,
When I changed the oil pan on Double Trouble I removed the transmission and final drive as an assembly so I can't answer your
question.
I said to disconnect both because I checked Parts Book 78Z / Section 8 - Engine / Page 8-13 / Figure 8.015 / Mounting - Engine and
wasn't sure how far you'd have to raise the front of the engine and what effect it would have on the rear mounts.
I did not want you tell you to disconnect just the front mount, lift the engine; and when doing so damage (tear) the rear mounts.
IIRC I had to raise the front of the engine a good 2 inches to get enough clearance to get the pan past the number 1 main bearing
cap.
Regards,
Rob M.
The Pedantic Mechanic
-----Original Message-----
From: eugene
Rob,
On #5, do both the front mounts and the rear mounts need to be disconnected? Or can just the front mount be disconnected, the rears
mount loosened, and the front of the engine lifted? Any guess as to how much lift is needed for the pan to clear?
eugene
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GMCnet mailing list
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Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
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| Re: [GMCnet] Name that tune? GMC Engine noise [message #287584 is a reply to message #287583] |
Sat, 19 September 2015 20:51 |
hal kading
Messages: 642
Registered: February 2004
Location: Las Cruces NM
Karma: 4
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Senior Member |
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Eugene,
If you can find someone who has an oil pan, have them measure the depth at the front. That should tell you the max you will have to lift the front of the engine less the existing clearance below the pan.
Hal Kading 78 Buskirk Las Cruces NM
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