how much hotter do engines get after you shut them

[meep]

recall studies years back that showed pistons could be running with temps up to 500-600 degrees, conrods up to 400, crank shafts up to 350. all this heat has to dissipate.

I had a volvo years ago that would run the cabin fan on its own in the summer time once parked. I could never figure out its routine. I'd park the car, everything would be off, walk out later and the fan would come on for 10 minutes and shut down. Someone "confirmed" (internet) for me that this was programming in that model to pull heat off the engine through the heater core. I haven't witness the s60 we have now do it yet.

M

 

[HTSS_TR]

Originally Posted By: DoubleWasp
It's a very vague question because as previously mentioned, because "engine" and "hotter" need to be defined more accurately.

Can engine coolant temperatures increase after shutdown? Absolutely. The engine's parts can store thermal energy that no longer has a path for rejection, and that thermal energy goes into the coolant, which no longer has an effective path of rejection, and it temporarily builds.

Agree, I observed coolant temperature increased(up to 15-20F) in my E430 and S2000 after shutdown with either Ultra gauge(in the S2000) or actual coolant temperature gauge of the E430.

 

[Alfred_B]

Originally Posted By: javacontour
I don't think the engine can get hotter as you are no longer adding heat to it. Or at least not at the rate you do while running.

But that heat is radiating throughout the engine. So parts that were cooled by the movement of fluids or air are no longer being cooled, so they pick up that radiated heat.

I.E. individual parts may get hotter, but the engine as a whole is not getting hotter. So while your valve cover may be getting hotter, the exhaust manifold is likely getting cooler as it's heat radiates away.


This.

 

[Ethan1]

Originally Posted By: IndyIan
I had an off track excursion in my old Neon on a track day which I was running high 230's with the heater on. So after a sudden stop and sitting for a while shut off, I limped it off the track and later checked my scangauge. It had recorded a max coolant temp of 268F. I didn't notice it boiling over so I don't know how accurate that number is, but that's what the ECU saw at some point.

Also if you look up how a barn of wet hay catches on fire, heat transfer isn't always as intuitive as you would think! Common sense would say its impossible, but its common knowledge that it happens.


Of course, the ECTS is measuring just the coolant at just one small area of the cooling system - it doesn't give any indication of the temperature of the oil pan, valve cover, different areas of the head, et cetera.

 

[meep]

Originally Posted By: HTSS_TR
Originally Posted By: DoubleWasp
It's a very vague question because as previously mentioned, because "engine" and "hotter" need to be defined more accurately.

Can engine coolant temperatures increase after shutdown? Absolutely. The engine's parts can store thermal energy that no longer has a path for rejection, and that thermal energy goes into the coolant, which no longer has an effective path of rejection, and it temporarily builds.

Agree, I observed coolant temperature increased(up to 15-20F) in my E430 and S2000 after shutdown with either Ultra gauge(in the S2000) or actual coolant temperature gauge of the E430.


same 15-20F increase observed with jeep I6 4.0

-m

 

[Gasbuggy]

Originally Posted By: meep
Originally Posted By: HTSS_TR
Originally Posted By: DoubleWasp
It's a very vague question because as previously mentioned, because "engine" and "hotter" need to be defined more accurately.

Can engine coolant temperatures increase after shutdown? Absolutely. The engine's parts can store thermal energy that no longer has a path for rejection, and that thermal energy goes into the coolant, which no longer has an effective path of rejection, and it temporarily builds.

Agree, I observed coolant temperature increased(up to 15-20F) in my E430 and S2000 after shutdown with either Ultra gauge(in the S2000) or actual coolant temperature gauge of the E430.


same 15-20F increase observed with jeep I6 4.0

-m



I see the same with our 2.5L Wrangler. Just over the weekend my girlfriend wanted a picture infront of an old truck parked on a city street. It sat for maybe 4-5 minutes. Temp gauge was past 210 on restart and quickly moved back to normal.

 

[CELICA_XX]

Originally Posted By: Robenstein
Originally Posted By: Olas
They don't get hotter, they just don't cool as quickly.


If internal heat is quickly being pulled to the outside, creating the illusion of a warmer engine post shutdown, they are cooling more quickly.


Are you saying that MORE cooling takes place when the engine is turned off, as opposed to a fully functional coolant system in circulation ?

 

[Olas]

Originally Posted By: CELICA_XX
Originally Posted By: Robenstein
Originally Posted By: Olas
They don't get hotter, they just don't cool as quickly.


If internal heat is quickly being pulled to the outside, creating the illusion of a warmer engine post shutdown, they are cooling more quickly.


Are you saying that MORE cooling takes place when the engine is turned off, as opposed to a fully functional coolant system in circulation ?


Although combustion produces heat, the waterpump & rad do a good job of rejecting heat. You shut the engine off and there is no more heat input so it will start to cool, but slower than it would if the water pump were turning (with engine off)