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| Engine Runs Hotter than usual [message #335080] |
Fri, 13 July 2018 21:12  |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
Karma: 1
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I set off on a trip the Canada to join GMC 49'ers on a rally to the Canadian Rockies.
10 miles down the road I noticed that the engine was running around 10 degrees hotter than usual and would spike into the 205 region and it wasn't hot outside. Normally it would be running around 185 to maybe 195.
I took a recent trip up the coast and it was running as usual, so this is a sudden change.
So, cancel the trip or fix it quickly. The work evolves:
So far I've checked the fluid - full to the top.
Concerned that the thermostat was bad - replaced it with a Robertshaw I purchased from Jim K - little change
Concerned that the temp sensor had failed - replaced it, little change.
Checked the lower radiator hose to see if it had collapsed - it was good.
The water pump is not leaking.
The fact that this came on suddenly has me thinking it isn't something like the radiator clogging.
Anyway, I'm hoping for suggestions as to what to do next. New radiator and water pump come to mind unfortunately.
Oh GMC Gurus, Save me and my trip with your advice!
Thanks,
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: [GMCnet] Engine Runs Hotter than usual [message #335081 is a reply to message #335080] |
Fri, 13 July 2018 21:26  |
James Hupy
Messages: 6806
Registered: May 2010
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Fan clutch comes to mind. Other things might be blown head gasket, bad
pressure cap on the radiator.
Jim Hupy
On Fri, Jul 13, 2018, 7:22 PM Jack Christensen wrote:
> I set off on a trip the Canada to join GMC 49'ers on a rally to the
> Canadian Rockies.
>
> 10 miles down the road I noticed that the engine was running around 10
> degrees hotter than usual and would spike into the 205 region and it wasn't
> hot
> outside. Normally it would be running around 185 to maybe 195.
>
> I took a recent trip up the coast and it was running as usual, so this is
> a sudden change.
>
> So, cancel the trip or fix it quickly. The work evolves:
>
> So far I've checked the fluid - full to the top.
> Concerned that the thermostat was bad - replaced it with a Robertshaw I
> purchased from Jim K - little change
> Concerned that the temp sensor had failed - replaced it, little change.
> Checked the lower radiator hose to see if it had collapsed - it was good.
> The water pump is not leaking.
>
> The fact that this came on suddenly has me thinking it isn't something
> like the radiator clogging.
>
> Anyway, I'm hoping for suggestions as to what to do next. New radiator
> and water pump come to mind unfortunately.
>
> Oh GMC Gurus, Save me and my trip with your advice!
>
> Thanks,
>
> --
> Jack Christensen - K6ROW,
> '76 Glenbrook/Clasco - "The Silver Bullet",
> Sebastopol, CA
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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| Re: [GMCnet] Engine Runs Hotter than usual [message #335082 is a reply to message #335081] |
Fri, 13 July 2018 21:51 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
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James Hupy wrote on Fri, 13 July 2018 21:26Fan clutch comes to mind. Other things might be blown head gasket, bad
pressure cap on the radiator.
Jim Hupy
Could also be something as simple as the weights in the distributor finally froze, so that they don't advance the centrifugal timing. Engine will heat up without sufficient advance. Pull the cap and check the weights. Maybe....maybe not. JWID
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Fri, 13 July 2018 21:53] Report message to a moderator |
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| Re: [GMCnet] Engine Runs Hotter than usual [message #335084 is a reply to message #335082] |
Fri, 13 July 2018 22:00 |
Burt and Faye curtis
Messages: 256
Registered: June 2012
Karma: 4
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Jack,
Get it fixed quick if you can. We are missing you. Group is currently in
Calgary baking in the heat. Looking g forward to the cool of the Rockies.
Fay Curtis
Traveling with the other 59ers in a borrowed 73 Canyonland
Stampede Dome Calgary, Alberta
On Fri, Jul 13, 2018, 8:52 PM Larry wrote:
> James Hupy wrote on Fri, 13 July 2018 21:26
>> Fan clutch comes to mind. Other things might be blown head gasket, bad
>> pressure cap on the radiator.
>> Jim Hupy
>
> Could also be something as simple as the weights in the distributor
> finally froze, so that they don't advance the centrifugal timing. Engine
> will
> heat up without sufficient advance. Pull the cap and check the weights.
> Maybe....maybe not. JWID
> --
> Larry
> 78 Royale w/500 Caddy
> Menomonie, WI.
>
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| Re: Engine Runs Hotter than usual [message #335092 is a reply to message #335080] |
Sat, 14 July 2018 04:58 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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While all of the previous suggestions are good and should be checked, I think we are avoiding the probable cause. That is a clogged, restricted coolant flow through the radiator.
I would pull the thermostat and throw it in a pan of hot water on the kitchen stove. Start heating the water and watch the thermostat to see at what temperature it really opens. Use a mercury type thermometer if you have one. I have seen many bad "new" thermostats.
If the thermostat checks OK then it is time to consider flushing, cleaning, or replacing the radiator.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Engine Runs Hotter than usual [message #335097 is a reply to message #335080] |
Sat, 14 July 2018 06:57 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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I'm with KenB. A blown gasket or sticking 'stat would leave some air in the radiator, would it not? Sticking weights could cayuse this to appear fairly quickly. I bought a little ins[pection camera off eBay or either Banggood - forget which - which could be used to inspect the radiator per Bob Dunahugh's suggestion. (Actually, I bought it to see if you could tell any difference with colant in the radiator since it's waterproof haven't had a chance to try it there yet). It was less than 20 bux, works on a laptop or a smartphone. You might try that and have a look if the timing is working correctly.
Also, while not a great idea for aluminum engines, 'fast flush' properly used might clear the crud if there is some in the radiator. These old iron engines will withstand the stuff. For the price of it and a couple hours you might find a solution. Beyond that, have a radiator shop take a look. I've had two recored with good results.
--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: Engine Runs Hotter than usual [message #335100 is a reply to message #335092] |
Sat, 14 July 2018 07:18 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
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Ken Burton wrote on Sat, 14 July 2018 04:58While all of the previous suggestions are good and should be checked, I think we are avoiding the probable cause. That is a clogged, restricted coolant flow through the radiator.
I would pull the thermostat and throw it in a pan of hot water on the kitchen stove. Start heating the water and watch the thermostat to see at what temperature it really opens. Use a mercury type thermometer if you have one. I have seen many bad "new" thermostats.
If the thermostat checks OK then it is time to consider flushing, cleaning, or replacing the radiator.
Good suggestion here. Sometimes we miss the obvious. If the radiator is clogged, those spots in the radiator will run cooler than the rest of the radiator. Hard to do in this application, so DON'T do this with the engine running, but try feeling the radiator with your hand or use a thermal heat gun to check temps. A lot of cool spots or one large cool spot indicates no water flow...therefor cooler and clogged.
Larry
78 Royale w/500 Caddy
Menomonie, WI.
[Updated on: Sat, 14 July 2018 07:19] Report message to a moderator |
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| Re: Engine Runs Hotter than usual [message #335103 is a reply to message #335080] |
Sat, 14 July 2018 08:35 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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There is a lengthy proceedure to test the fan clutch in GM service manual. A quick go/ no go test is that you must have "fan roar" for a couple mins at cold startup high idle after sitting overnight. This is until the fluid redistributes to the non working chamber after 1 to 2 mins of rotation. If sufficient fluid has leaked out this roar will be diminished. Your non engaged speed will be below spec and it may not engage on demand . As a side note I found the 3 NAPA numbers in the interchange are made in USA. I would choose the muddle number if I were buying one.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Engine Runs Hotter than usual [message #335104 is a reply to message #335080] |
Sat, 14 July 2018 08:47 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Here is a quick "fix in a can" that if it helps gets you going. Take a mechanics mirror and light and get a glimpse of the bimetallic spring on front of clutch.
GM says slight leaking of fluid here is normal. However the oily spring gets packed with road grundge due to the huge volume of aiir passing by to where it does not change size well. Spray the coiled spring with WD-40 with extension on can. Wait. Spray again. Then try to give the dirt a good flush away action with final spray. Avoid belts and pulleys though it will wear off. Easy cheap fix if it works and saves clutch swap to continue your trip.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: Engine Runs Hotter than usual [message #335108 is a reply to message #335104] |
Sat, 14 July 2018 09:04 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
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Another possibility that I haven't heard mentioned is an electrical problem with the gauge. The reason I mention this is that the problem came on so suddenly.
To test this theory, shoot the thermostat housing with a thermal heat gun and see what the temperature coming out of the engine actually is. It might just be normal, but your gauge is trying to fool you.
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: Engine Runs Hotter than usual [message #335111 is a reply to message #335080] |
Sat, 14 July 2018 09:29 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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There's a 'get home' if the fan clutch is toast. Take a couple of small sheet metal screws and drive them into the space between the water pump shaft and the clutch housing. This will jam the fan on and you will listen to it all the way... but it will keep turning. Be sure you're intending to replace the clutch before you do this - cos you ARE going to replace it afterwards.
--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: Engine Runs Hotter than usual [message #335126 is a reply to message #335080] |
Sat, 14 July 2018 13:43 |
captjack
Messages: 271
Registered: February 2010
Location: Sebastopol, California
Karma: 1
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Thanks for all the suggestions which were very helpful.
The fan clutch is OK, the distributor is OK. I used an infra red thermometer on the manifold near the thermostat (which I checked - both were OK) which showed the same temp as the electronic gauge. The oil looks clean and there's no bubbling in the water in the radiator. I could do a compression test, but I don't really think it's a blown headgasket at this point.
So, the more I cogitate over all the info, I'm afraid I have to agree with Ken. The radiator is the problem, so it's a trip killer. I'm not desperate enough to pour magic elixers into the engine and hope they work. But, all is not lost. The Canadian Rockies will still be there in the fall and with a lot fewer people. What I'll miss most is delaying my trip to visit my Canadian Cousins, who like me, are getting older.
So I either need to get the existing radiator cleaned or get one an aluminum one. My GMC engine has probably at least 110K miles on it and the oil pressure is low (doesn't always meet the 10 psi per 1000 RPM). Oil tests have been pretty good (I just had one) except for iron which is consistently around 80 compared to the "Universal Average" of 37. Maybe all this is nature's way of telling me it's time to get the engine rebuilt, radiator done, etc.
Thanks again!
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: Engine Runs Hotter than usual [message #335128 is a reply to message #335080] |
Sat, 14 July 2018 14:42 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Particularly if I was going to redo engine and radiator fairly soon, I'd try the fast flush. Either it works or it doesn't, you hazard a few bucks and most of a day draining flushing and refiling/ If it works you make the rally, if it doesn't you've lost nothing.
--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] Engine Runs Hotter than usual [message #335131 is a reply to message #335126] |
Sat, 14 July 2018 15:34 |
k2gkk
Messages: 4452
Registered: November 2009
Karma: -8
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Senior Member |
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There is an aluminum radiator for the GMC on eBay. Apparently a manufacturer and currently 10% off "normal" list price.
Item number is: 163053560599
D C "Mac" Macdonald
Amateur Radio K2GKK
Since 30 November '53
USAF and FAA, Retired
Member GMCMI & Classics
Oklahoma City, OK
"The Money Pit"
TZE166V101966
'76 ex-Palm Beach
k2gkk + hotmail dot com
________________________________
From: Gmclist on behalf of Jack Christensen
Sent: Saturday, July 14, 2018 13:43
To: gmclist@list.gmcnet.org
Subject: Re: [GMCnet] Engine Runs Hotter than usual
Thanks for all the suggestions which were very helpful.
The fan clutch is OK, the distributor is OK. I used an infra red thermometer on the manifold near the thermostat (which I checked - both were OK)
which showed the same temp as the electronic gauge. The oil looks clean and there's no bubbling in the water in the radiator. I could do a
compression test, but I don't really think it's a blown headgasket at this point.
So, the more I cogitate over all the info, I'm afraid I have to agree with Ken. The radiator is the problem, so it's a trip killer. I'm not
desperate enough to pour magic elixers into the engine and hope they work. But, all is not lost. The Canadian Rockies will still be there in the
fall and with a lot fewer people. What I'll miss most is delaying my trip to visit my Canadian Cousins, who like me, are getting older.
So I either need to get the existing radiator cleaned or get one an aluminum one. My GMC engine has probably at least 110K miles on it and the oil
pressure is low (doesn't always meet the 10 psi per 1000 RPM). Oil tests have been pretty good (I just had one) except for iron which is consistently
around 80 compared to the "Universal Average" of 37. Maybe all this is nature's way of telling me it's time to get the engine rebuilt, radiator done,
etc.
Thanks again!
--
Jack Christensen - K6ROW,
'76 Glenbrook/Clasco - "The Silver Bullet",
Sebastopol, CA
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| Re: Engine Runs Hotter than usual [message #335132 is a reply to message #335080] |
Sat, 14 July 2018 15:49 |
Chris Tyler
Messages: 458
Registered: September 2013
Location: Odessa FL
Karma: 7
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On mine there are tow gauges for water temp. One is engine t, the other is after the radiator.You can see the drop when the fan kicks on.
My PO was a gauge freak- he was a VN era B52 and retired airline pilot and used to monitoring a lot of widgets
76 Glenbrook
[Updated on: Sat, 14 July 2018 15:50] Report message to a moderator |
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| Re: Engine Runs Hotter than usual [message #335153 is a reply to message #335126] |
Sun, 15 July 2018 01:19 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Here is my suggestion. It only takes a few hours to get that radiator
out of there. It really takes two (or more) people. So call a fix it
day at your place and post an open invite to any GMCer to come and help. Then take
radiator to a local radiator shop and have them test and clean it.
Then last time my radiator was out Rob Mueller called a fix it day at my
hangar. A bunch of GMCers stopped by and they did the job while I took a
had to do trip to Cincinnati and back. We had GMCers from 4 states and one
province here. They did the job including taking it to the radiator
shop in one afternoon so I could go to a GMCMI rally when I returned
from Cincinnati.
The time before that when I had it out was at a GMCMI
rally in Delaware. Again a bunch of GMCers including Colonel Ken and
Emery helped with the swap and we did it in an afternoon with lot of
on lookers.
We did Dan Gregg's at Bean Station in one afternoon.
Get is out and take it to a radiator shop. Then you will know what
you have to do and what your options are.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Engine Runs Hotter than usual [message #335164 is a reply to message #335080] |
Sun, 15 July 2018 09:57 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Fred, that's quite true - but it's fixing symptoms instead of fixing the problem. Pull it out, have it inspected and whatever's needed done to it, put it back, and then use Redline and Evans >after< you've determined there are no further leaks or cooling problems. The system is quite capable when it's working correctly as supplied.
--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] Engine Runs Hotter than usual [message #335176 is a reply to message #335164] |
Sun, 15 July 2018 11:17 |
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Anonymous
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As he said “The system is quite capable
when it's working correctly as supplied.”
So why put in Redline and Evans after it’s fixed. 99.99% or so of the GMCs work fine with a good regular ethylene glycol coolant (Prestone and others).
I would never consider changing to those products. Using those seem like one is just trying to mask a problem. And, do “water wetters” actually work?Ethylene glycol does the same thing and it’s not another additive than can actually interfere with the antifoam, water pump lubricant, and rubber anti-swell additives that are already formulated into a good quality coolant which has been tested by the manufacture to work properly. Once you introduce an additive from someone else you don’t know if it’s compatible with the antifreeze package.
Emery Stora
77 Kingsley
Frederick, CO
> On Jul 15, 2018, at 8:57 AM, Johnny Bridges via Gmclist wrote:
>
> Fred, that's quite true - but it's fixing symptoms instead of fixing the problem. Pull it out, have it inspected and whatever's needed done to it,
> put it back, and then use Redline and Evans >after< you've determined there are no further leaks or cooling problems. The system is quite capable
> when it's working correctly as supplied.
>
> --johnny
> --
> 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" - ol Andy, paraphrased
>
>
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