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Bad thermostat?

pjm8047

pjm8047

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what would cause top radiator hose to get really hard engine temp to rise fast when at idle and coolant going into over flow tank. At one point the gauge went to hot really fast the drop back down to normal never seen that before. It’s a 71 rr with a 4 row aluminum radiator. Could it be a bad thermostat not opening all the way? Someone told me not to run a thermostat at all.
 
If we were talking 2.2l mopar I'd say head gasket. There are test strips for hydro carbon in coolant.
 
I just had one of my 74 chargers do that. .drove it ten miles and then started heating up fast. It's cooling system is all brand new. I figured it was a crap thermostat so I replaced that. I took it for a spin with no heating issues so that must have been it
 
With the engine cold , take off the radiator cap

Run the engine

You should not have any coolant flow across the top of the radiator when cold

As the thermostat starts to open at its rated temp you should have a steady flow of coolant across the top of the radiator

If the thermostat is rated for say 180 degrees , and your temperature is at 180 degrees - 190 - 200 and you have zero coolant flow

Your thermostat is stuck in the closed position

You should start to see and maintain a steady coolant flow across the top of radiator at 180 degrees


If you have steady coolant flow with the engine stone cold at idle , your thermostat is stuck in the open position

A nice accurate temp gauge is nice or a cheap temp laser thermometer gun from harbor freight

Take temp at upper and lower radiator hoses

Peace
 
Last edited:
Yup, make sure it burps and run a quality 180 like a Stant a Superstat.
 
I bought a 160 thermostat. Too low? Alot of websites i read say it could be a head gasket no white smoke or milky oil and no leaks. U think bleeding air out will fix the problem? Only gets hot at low rpms. Yesterday first time i saw this the gauge spiked to H really fast for a second and dropped right back down. What’s that about?
 
No loss of coolant and exhaust does not smell sweet probably not a head gasket. Try a shop that will give you a hydro carbon test strips for your coolant. You can also buy a package of these.
 
I installed aftermarket overflow tank. Last night I topped it off and this morning it was empty this mean I am low on coolant? The radiator seems full when cold.
 
So I pressure tested the cooling system any found no leaks. I ended up removing the thermostat and now it’s running cool. The thermostat was stuck closed.
 
So hopefully now, you can replace the thermostat with a quality 180* and be back Moparing...
 
coloradodave said:
So hopefully now, you can replace the thermostat with a quality 180* and be back Moparing...
Click to expand...
Im not going to use a thermostat. Don’t use the heater and it’s running fine without one.
 
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