65GGvert

Need some help. I'm confused. I have an original 72 with 350, 4 speed, A/C car. Since I've owned the car (couple of months) the coolant temp has been reading around 150 on the gauge. I drove it this morning in 30 degree temp and it still read 150 and the heater blew cool air. I assumed the thermostat would be missing or stuck open, so while installing a new Borgeson power steering kit, I decided to replace the water pump (noisy) and the thermostat. The thermostat in the car was a 180 and looked fine. Put the new one in anyway along with the water pump and power steering. When finished I let the car idle for about 30 minutes and it never went over 150 on the gauge, so I shot the thermo housing with two different IR guns. Both read 155 degees and the upper radiator hose read 148 and just warm to the touch. How could the coolant be bypassing the new thermostat? The intake below the thermo housing read a little higher, around 170. Any idea what would cause the temp to be 150 going into the top hose through the thermostat? Heater still doesn't blow warm air either.

SWO vette

Got the same problem with my 72. I just replaced the thermostat and heater core so we shall see once the roads clear up.

65GGvert

No suggestions?

capevettes

All of my old Corvettes run cold in the winter when temps are cold. Maybe you Southern guys just aren't used to cold temps . It's not uncommon for my cars to run around 160 if it's under 30 degrees outside. I don't view it as a problem. You may be glad it runs a bit on the cool side once the warm weather arrives.

imariver

Any thermostat can "look" fine, did you actually test it before you put it in?

Mick71

That was my first thought as well. Running too cold, what else could it be but a stuck open thermostat?

sgt kohler

I live in east texas. this past summer I replaced my temp guage on my 77 it was broke. after the change it was reading reading 180 and all was fine . checked it with a heat gun all over the engine and it read 180. I then changed the radiator fluid and the thermostat as the car had been in storage for 15 year. I put a new 180 fail safe in it and my temp now on a hot day stays around 150. im not complaining because the heat in the cabin has been greatly reduced. my heater works fine and will keep the car warm on the cool days. my radiator is a stock style that had been replaced when the car was put up in storage. I also replaced the clutch fan. I have hooker side pipes on it and I don't seem to have the heat under the hood like I used to maybe the new fan and thermostat fixed it.

65GGvert

The old thermo and two new thermostats all reading 150? If I got three bad thermo's I'll just take my lumps. I'm not pulling it again for now. The only reason I'd like to get the temp up a little is so the heater will blow warmer air. I just don't understand how the engine can run even in cold temps with a closed thermostat and not heat up to 180. I've owned many cars and many Corvettes and this is the first time I've had a too cool issue, though I've had several the other way.

mikem350

If it runs cold, below what the thermostat is rated at...it has to be something with the thermostat. I am not positive, but if its installed backwards, maybe it could cause a problem?

You sure its installed properly...and is a 180? The rated temp is when it just starts to open. Like your readings would indicate a 160

65GGvert

Yeah, I took out a 180 and put in a 180, then got a more expensive 180. No change. Next time I get the car out, I'm going to let it run a while and look in the radiator to see if coolant is moving. If it is, the thermostat has to be open. I've just never seen a Chevy engine that didn't get up to 180 pretty quickly with a 180 thermostat. I thought the gauge or sender was off, but IR gun matches. The center of the intake manifold beside the carb on the driver's side was reading about 185. Exhaust manifold reads 575. I checked that after I accidentally brushed it with a finger and smelled my skin smoking.

Greatsteaks

150 ° should still blow warm air I would think. Sure your heater core valve is working?

gbvette62

Back in the 70's, when we were still using a Corvette as a daily driver, I use to block off part of the radiator with a piece of cardboard, in the winter. It was the only way I ever got them to warm up enough, to get any heat out of the heater. The new 81 we bought, was the first Corvette we owned, that I didn't have to do it too.

Jud Chapin

Perhaps I'm missing something here, but if you have a 180 degree thermostat that is operating properly, it won't open until the coolant temp is 180. This is the minimum temp the engine should run at after warm up. If your gauge is correctly reading 150 degrees, that would mean the coolant is not circulating thru the block, which produces a tremendous amount of heat. This makes no sense to me. I would suspect a faulty gauge and/or wiring.

65GGvert

If it was the gauge or wiring, the IR gun wouldn't show 150 degrees on the thermostat housing. The upper radiator hose is barely getting hot, 145 degrees or so.

Jud Chapin

Does the temp gauge show 150 after driving the car for long periods?

65GGvert

Just changed it yesterday. I drove it about 30 minutes and idled for about 10. Haven't had it on the road yet, but with the original stat and pump, it read 150 also. (Even at 70 on the interstate)

Paul L

This does not make sense. The t-stat will hold the temp at 180*F until it opens. It must be upside down.

65GGvert

It isn't, but even if it was how would it be allowing coolant to pass? It would still be closed. I'll take a look at the coolant to see if it's flowing before I do anything else.

Jud Chapin

I just find it hard to believe that with combustion chamber heat of around a few 1000 degrees that the engine temp is 150 with uncirculating coolant.

Paul L

If the coolant was not flowing then engine temps would lead to a massive heat/pressure build-up and blow-out somewhere, e.g. upper rad hose. I don't know what is happening with your car.

*Edit* - In late October I drove my 1974 to winter commercial storage. It was 20*F that day. After 3-4 minutes of warm-up I started out after the divorced choke kicked down. Storage was about 15 minutes/10 miles away. The temp gauge showed 180*F when I arrived.