The Stovebolt Site Forums The Shop Area Engine Shop Thermostat overheat problem

Ok got an overheat issue but let explain, I've got a 41 Chevy with a 50 216 engine. It's overheating and I know why but not sure what to do, it was overheating before cause of junk in the block stopping up the radiator, but they are clean now, flushed em, took the plugs out, everything. Also the water pump is new, and everything is sealed and no leaks.
Ok I know everyone says don't run without a thermostat, but I have been while I've been flushing it and it's been fine now, no over heats anymore, today I put a 180 degree thermostat in, and it ran warm, (it's sopose to run around 180 right?) and it ran at about 185-190 with that thermostat, and shut the engine off it go up to over 200 till it cooled. So popped that thermostat out and put 160 and it ran even hotter, over 200 the whole time, and steam came out the overflow with that one when I shut it off. And yes both had 1/8th holes drilled. So runs fine without stat, warm with 180 and way to hot with 160.... What do I do/try?

The temps you post that the 180 degree thermostat are about the right range for that temperature thermostat. The temperature rating is the temperature that they open. Going higher when the engine is shut down is normal. The 160 degree thermostat might be a dud just from the description of the symptoms.

You didn't say whether or not water is boiling out while it's running? What radiator do you have? Stock? What pressure radiator cap are you using? Water pump good? All this matters for us to help you understand what's going on and what to do to fix it.

Ian, I agree with Longbox. It sounds like you were OK until you changed the thermostat. The temps with the 180 is perfectly normal. Even the temp gauge could be off a few degree's.
(sounds like the 160 thermostat is a dud or upside down)

For now, I'd put the 180 back in and monitor the temp as you were doing. If it remains the same as you mentioned then I think your good to go. A couple things you may want to check is to make sure your fan belt is tight and not slipping on the new water pump and be sure your radiator cap is appropriate for the radiator your using.
.... or you using coolant/antifreeze, or have you just been running plain water during your test runs. If using plain water then switch to coolant

...another thought that comes to mind is the heater core. Is it clean or did some trash from it get into the radiator...or perhaps you have it by-passed?

Hope some of these ideas work for you. Good luck and keep us posted.

Martin,
It is all stock and the water pump is new

Thanks for your help, i have put the 180 back in and the 160 wasnt upside down but I think it's a dud cause it's was pretty dry on top except where I put the vent hole.
Checked fan belt and it's tight, and the heater core seems clean.
One thing you mentioned and I did not think about was water, I've been running straight water to clean it out and test. So since it's clean in goes the antifreeze.
Thanks for your help everyone, I'll let you know what happens!

make sure no air in radiator

Doesn't the 1941 cooling system have a non-pressurized radiator? If so, running a 180 degree stat might be pushing the envelope a little toward a boil-over before the thermostat opens. I'd recommend installing another 160 and see if the one you took out was bad. Also, a zero pressure radiator needs to have a considerable amount of expansion room in the top tank- - - -keep the coolant just above the level of the radiator core to keep coolant from being puked out of the overflow.
Jerry

One other thing to consider is if the ignition timing might slow. I got a call on a 1940 Chevy 216 that would overheat quick on start up and saw the distributor had turned. Reset the ignition timing and his problem went away.

But you could hear the engine sounding like it was running under a load at idle and would just barely run.

Hope it's just thermostat related.

Always easy to put a t'stat in a pan of water in the kitchen and watch it open, best done when woman of house is elsewhere.

If using original radiator, be sure to only use 3 or 5 psi cap, more will hurt radiator.

Ed

Ian, I agree with Ed above. You need to check the thermostat in a pan of boiling water with a thermometer. I was running a 180 degree thermostat in my newly rebuilt 52 GMC and was concerned with it running at or near 200 degrees. After testing it I found started to open at 180 but was not fully open until 200. I think that the number stamped on the thermostat Is actually the temperature that it starts to open rather that the fully open temperature l changed to a 160 degree and now it runs comfortably at 180 degrees.
Mike.

Hi everyone I put the 180 stat back and put antifreeze in, and it's runs just over 180, like 184-185 or so, and idles two or three degrees higher and constant running it, like constantly going 50 mph or so it gets down to 180 so she seems to be okie dokie!

Sounds/looks right, Ian Ring