Running hot... or maybe not?

[Curtisje]

My 1985 M1028 is running a little hot, 220-240 range. I recently installeda new radiator (4 row) and hoses. I installed an electric temperature gauge where the dummy light sensor was. I installed a new 180 degree thermostat and it continues to run 220-240. I'm considering a 160 degree thermostat but thought maybe I don't have my temperature gauge plugged in to the right spot for this. Any advice is welcome.

 

[richingalveston]

Have you checked it with a IR temp gun. It may not be that hot, my temp gauge is reading hotter than it actually is. Electric gauges can have issues.
being in the same spot as the stock gauge should be correct.
I would start by getting some other measurements from a separate source.
Going to a lower temp thermostat should not help, in theory it would never close.

 

[Curtisje]

Have you checked it with a IR temp gun. It may not be that hot, my temp gauge is reading hotter than it actually is. Electric gauges can have issues.
being in the same spot as the stock gauge should be correct.
I would start by getting some other measurements from a separate source.
Going to a lower temp thermostat should not help, in theory it would never close.

Thanks Rich. You are correct. My gauge is showing 20+ degrees above actual engine temp. I have another sending unit I'll install. If that doesn't work I guess I'll go back to mechanical.

 

[Barrman]

I know you have a 180° thermostat. However, 192°-198° is right where the engine lives with the stock 195° thermostat. Which starts to open at 192° and is fully open at 203°. Are you sure it is a 180° thermostat?

 

[Welder1]

The thermostat is to set the minimum temperature for the engine. The cooling system will reach equilibrium of heat generated with radiator ability to reject the heat. If the high temperatures are due to system capacity them opening the thermostat at a lower temp only delays the time it takes to get to equilibrium. You really need to determine what the true coolant temps are then move from there.

 

[sneekyeye]

It's possible to install the thermostat backwards, just need to confirm this isn't the case here.

 

[chevymike]

It's possible to install the thermostat backwards, just need to confirm this isn't the case here.

It is possible.

 

[cucvrus]

Peak of thermostat faces the radiator. That was easy. Good Luck.

 

[Curtisje]

It is a 180 degree thermostat. It is installed correctly. The gauge isn't giving me an accurate reading so I'll begin with replacing the sending unit since I have one in the garage.

I do appreciate all the advice.

 

[Curtisje]

The thermostat is to set the minimum temperature for the engine. The cooling system will reach equilibrium of heat generated with radiator ability to reject the heat. If the high temperatures are due to system capacity them opening the thermostat at a lower temp only delays the time it takes to get to equilibrium. You really need to determine what the true coolant temps are then move from there.

A 180 degree thermostat begins to open within three degrees of 180, so 177 to 183. By 200 degrees, the thermostat is fully opened. The operation of the thermostat, open to close, is a range of about 20 degrees, so with different temp ratings, you can fine-tune the run temp of your vehicle.
Using a thermostat of a lower temperature will lower the operating temperature of the engine because the thermostat will be fully open at a lower temperature.

 

[Curtisje]

Well... I replaced the sensor this morning and then drove to work. No change. I replaced the gauge this afternoon and drove to the bar. It reads a little hotter. I picked up a mechanical gauge at the part store and will install it tomorrow.

 

[sneekyeye]

You know, what could be happening is there may be a poor ground side connection between the engine, battery, and cab grounds adding just enough resistance for it to read 20 or 30 degrees too hot. I don't know if it works in that way, but maybe.

 

[Keith_J]

Are you getting good coolant flow? Get a bucket, remove the heater hose from the pump , block the return line and crank the engine. Impellers do corrode.

 

[Curtisje]

You know, what could be happening is there may be a poor ground side connection between the engine, battery, and cab grounds adding just enough resistance for it to read 20 or 30 degrees too hot. I don't know if it works in that way, but maybe.

Maybe but I don't think so. I replaced it with a mechanical gauge. I'll drive it to work this week and report back.

 

[Curtisje]

Are you getting good coolant flow? Get a bucket, remove the heater hose from the pump , block the return line and crank the engine. Impellers do corrode.

I think I am because it will hold a constant temperature while driving. The gauge IS giving me a false temperature so I have to fix that first.

 

[Curtisje]

My electrical gauge shows this while cruising on the highway.

 

[Curtisje]

I replaced that this morning with a new mechanical gauge and now it reads accurately.



And while pulling a grade...


And sitting at the stop light...


Problem solved, problem staying solved. On to other projects. Thanis for the advice and have a great weekend.

 

[Barrman]

That looks correct now. 190°-198° sitting still or running on flat ground. Jumping to 202°-208° on big climbs.

 

[cucvrus]

I never worried about the temperature with an idiot light. When I added the gauge on a few units that became another thing to worry about. I kept the idiot light hooked up when I added the gauge and it never flickered when the gauge showed hot. I pulled temperature for the gauge out of the right rear head. After that I never bothered with the gauge. The light worked for me. I like gauges but they just add to the guess work. Looks good I hope it all works out.

 

[chevymike]

Yeah, idiot lights are exactly that. I lost an engine in my '64 Chevy II wagon because by the time the idiot light came on, it was too late. Rebuilt engine and promptly put full gauges in. Will no longer have an older vehicle without adding high quality gauges. Cheaper than rebuilding an engine.