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Engine High Temp [message #370215]

Wed, 27 July 2022 20:53

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Gentlemen,

I just road tested my GMC. It had sat for 30 years and had 8,000 original miles. The engine is running great, but hot. The analogue guage indicated 225 degrees and steady. Up hill and down, all the way to 60 MPH and coasting. The Digi panel reports High engine temp, alarm and red emer. light.

The coach has a new 195 degree thermostat, new water pump, re-cored radiator and all new lines and hoses. I spun the fan clutch and got less than 1/2 rotation. Dash temp guage indicates first 1/4.

Do you guys think this is a result of running in a 45 year old engine with low milage? Maybe surface friction from an old stored engine or perhaps something else?

Thanks in advance for any tips.

Take care,
Tom K

Tom & Oki Katzenberger, Kingsville, Maryland, 1977 23' Birchaven, 455 C.I.D., Micro Level, Howell EBL-EFI Spark Control, Macerator, York Air Compressor, 6 Wheel Disc, Quadra Bag, Onan W/Bovee Ignition

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Re: Engine High Temp [message #370220 is a reply to message #370215]

Thu, 28 July 2022 09:48

Matt Colie

Messages: 8547
Registered: March 2007
Location: S.E. Michigan

Karma: 7

Senior Member

Tom,

Engine coolant out temperature should be very responsive to the engine load. The fact that it is hanging at 225°F says that the system controls are working. I would believe that the aftermarket analog and the digipanel are reading true. The fact that the OE instrument reads 1/4 is about what I would expect. I don't know if you know, but 1/2 scale on that is about 250°F coolant out and that is getting dangerous.

If the system maintains that, it would not give me reason to worry. It might be uncomfortable. The additional heat in the engine bay may lead to vapor lock and other undesirable things, but it will not kill the engine.

The fact that a new thermostat was installed is interesting, but there is no reason to trust it.

Were I dealing with this I would do two things:
I would shoot the thermostat housing with the IR gun I use to measure wheel bearing temperatures.
(After it cooled down)
I would do the old pot on a stove test of the thermostat.

As said, the fact that the coolant temp is stable there says things are working as they should. I would be wanting to gather a lot more data.

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: Engine High Temp [message #370221 is a reply to message #370215]

Thu, 28 July 2022 10:23

JohnL455

Messages: 4447
Registered: October 2006
Location: Woodstock, IL

Karma: 12

Senior Member

1) New thermostat. New thermostats are often junk. I highly recommend the Flowkooler 195.
2) fan clutch test. Your “spin test” tells really nothing valuable other than not frozen or not 100% free wheeling
A) at cold start after sitting and high idle, you must hear FAN ROAR for at least 2 mins that then subsides. Overnight gravity puts the silicone fluid into the working chamber causing fan engagement roar. Cold, the valve is set to pump fluid into the non working chamber. Takes a couple mins as fluid cold. This test shows that there is sufficient fluid in the clutch. If no fan roar at cold start, replace clutch. If it passes go on to B.
B) this test is fairly involved with restricting air and timing results (see manual) but in simple terms you should hear fan roar at the temps you are getting. If not then the bimetalic spring may be caked with road grime and not rotating. I have sprayed with WD-40, waited then sprayed again to flush grime away successfully. Or the clutch could be getting poor heat signal from underfilled coolant or not fully opening stat. Of course a missing or missalligned shroud will dilute the heat signal with cold air and prevent clutch action. Lastly a bad cap return valve or porous hose to overflow can pump coolant out hot, then return air during cool down. This misleads you into thinking cooling system is full but it is not. Again giving poor heat signal to clutch.
After all that sitting, there is a very very good chance your distributor vacuum and mechanical advance is gummed up. Retarded timing will cause overheat for sure.
I’m assuming you have fresh 50/50 Ethylene glycol coolant as you did rad work.

John Lebetski
Woodstock, IL
77 Eleganza II

[Updated on: Thu, 28 July 2022 10:35]

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Re: Engine High Temp [message #370222 is a reply to message #370215]

Thu, 28 July 2022 12:16

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

John and Matt,

I will follow both instructions and get back. I don't hear the clutch fan roar and I will shoot the thermostat with the digital thermometer. I do feel the same as both the analog and Digi panel are probably more accurate then the dash gauge.

Thanks guys.

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Re: Engine High Temp [message #370228 is a reply to message #370215]

Fri, 29 July 2022 15:03

Greg C.

Messages: 224
Registered: October 2019
Location: Knoxville, TN

Karma: 0

Senior Member

I would second checking the mechanical advance mechanism. I drove my coach 1000 miles back from Texas in July 2020 when I purchased it. It ran warmish the whole way, with ambient 90's temps and not a lot of power. While working on it when I got it home I discovered the mechanical advance weights were worn with elongated holes, and the shaft was gummed up with oil deposits and not advancing at all. I worked some Kroil down the shaft while manually moving the advance shaft until it loosened up. It now seems to run better and cooler. Of course, a new radiator core and Flow Kooler t stat helps I'm sure.

Greg Crawford KM4ZCR Knoxville, TN "Ruby Sue" 1977 Royale Rear Bath 403 Engine American Eagle Wheels Early Version Alex Sirum Quad bags

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Re: Engine High Temp [message #370231 is a reply to message #370215]

Fri, 29 July 2022 23:09

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Guys,

I should mention that the engine has EFI with EBL. I did shoot the thermostat housing with the digital thermometer and the analog gauge and digi panel gages are accurate as Matt said.

I purchased a new fan clutch. I will install it this weekend as well as a 9 pound cap. If the new fan clutch does not correct the issue, I will at least have a spare.

Thank you guys for your help I will let you know how Thing's work out.

Have a wonderful weekend,
Tom K.

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Re: Engine High Temp [message #370232 is a reply to message #370215]

Sat, 30 July 2022 08:21

RF_Burns

Messages: 2276
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Tom,

You likely know this, but you didn't mention it so I'll bring it up.

The EBL's What's Up Display (WUD) also shows the engine coolant temperature from a separate sensor. This will give you another verification of the engine temperature. You can also Log all the engine parameters by clicking on File > DataLog and giving the log file a name. Then you can play back the file at a later time for troubleshooting or just for fun!

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: Engine High Temp [message #370234 is a reply to message #370215]

Sat, 30 July 2022 19:50

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Bruce,

I have not brought the EBL up yet. I came out of the EBL with USB male adapter going into USB-C port on the tablet. I think I have to go into the tablet with A USB port instead of the USB C port. I will play with the EBL tomorrow to see if I can bring it up and I really appreciate the information on the additional data points that the EBL can give me. I'm going to replace the fan clutch. If that doesn't work, I will reinspect the whole system.. I'm hoping that the new re-cored radiator is functioning properly as everything else is new. I was also wondering if the new fiberglass fan shroud would cover the whole radiator and may help the system perform better. Also, if the fan clutch is defective I may split the fan shroud when I install the new clutch as it appears that the clutch are frequently a failure point.

Thanks again guys for all your help I will let you know how things worked out.

Take care,
Tom K.

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Re: Engine High Temp [message #370235 is a reply to message #370234]

Sun, 31 July 2022 01:42

Bill Van Vlack

Messages: 419
Registered: September 2015
Location: Guemes Island, Washington

Karma: 14

Senior Member

The EBL should work fine with either type of USB port. Go into device manager on the PC and find out which port appears when you plug it in, then set the WUD software for that port. If the PC also has the standard USB port, then just use whichever one is less likely to be used for something else. You can always switch back if you need to.

Bill Van Vlack '76 Royale; Guemes Island, Washington; Twin bed, full (DS) side bath, Brazilian Redwood counter and settee tops,455, 6KW generator; new owner a/o mid November 2015.

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Re: Engine High Temp [message #370238 is a reply to message #370215]

Sun, 31 July 2022 09:55

Tom Katzenberger

Messages: 399
Registered: June 2019
Location: Kingsville, MD

Karma: 4

Senior Member

Bill,

Thank you. I will follow your instructions. Wish me luck as I am not that tech savvy.

Thanks again,
Tom K.

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Re: Engine High Temp [message #370380 is a reply to message #370215]

Wed, 17 August 2022 14:29

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

Along with the above recommendations, I'd do a flush of the block. Drain off and save the nice new coolant, fill it with water and fast flush, run it, do it again,and see what the flushed water looks like. Keep flushing till it comes out clean. Flush backwards, hose into the thermostat housing and out the lower hose. It may of grown some scale inside sitting.

--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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