Engine Heating After Shutoff

Hi All,

Noticed something odd when driving home this evening (~74°F ambient temp). I recently replace my lack of thermostat with a new 160° stat from Kaiser Willys (I made sure to drill a hole in it to avoid air lock) and flushed the coolant when I did the replacement. Tonight when driving home I stopped for gas and when I went to start the Jeep back up I noticed the engine was at 200°F. After starting it back up it dropped right back down to 170°F. I had to make one stop on the way home and the same thing happened. I haven’t noticed this before—any thoughts?

 

Were you driving her hard just before you shut it down? Might have been exhaust manifold heat conducting back into the engine. Try idling a couple minutes before shut down to see if that helps.

 

Hmmm not too hard, but good idea indeed.

 

The exhaust manifolds on an engine can hold lots of heat. Many years ago I owned a 880 Ford dump truck with a 577 cu. in. gas motor. If you ran her hard, I have stepped out of it at night to see a red glow under the truck from the exhaust manifolds glowing red hot!

 

All engines do this to some extent. When you shut it off the water stops circulating to the radiator and the temp of the coolant in the engine rises.

I had a grand Cherokee that had a small crack in the radiator plastic. It wouldn't leak a drop while running, but a few minutes after shutting it off it would start squirting out. Pressure rose with the increased coolant temp.

 

I had this same question a few years back and Zoomer’s answer is right on. My Dauntless can easily raise 15-20 degrees after shutdown.

Restarting the engine the temperature drops quickly as the coolant starts flowing.

 

It's called heat soak. Every engine does it.

 

Thanks guys!

 

Piston aircraft engines can suffer from what is called "shock cooling" where the engine has been operating at the top of the cruise rated speed for an extended time. With the sudden chop of the throttle approaching the landing/decent the sudden cooling of the engine in the often below 0 temps can cause engine damage. Normal procedure is to throttle back gradually on approach to allow slower cooling of the cylinders.

 

Totally normal heat soak. You only have an issue when it doesn't come back down once started back up

 

Normal to an extent, there are some things you should look at, backflush the engine and heater core. Probably want to do a chemical flush of the block.
Verify the thermostat opens. Remove all air pockets from the engine.
40° is significant and may be an indication of hot internal components that is masked by an effective cooling system. You may be running lean or need to adjust timing a tad but seek a 2nd opinion in person. Is this the stock engine?

 

Also remember half of your cooling system is the engine oil. How is your oil level and what oil viscosity are you running? If your oil is not carrying heat away from the lower end you can have more heat soak since that heat is not cooled in the oil pan.