Hello my fellow Thirdgeners:
I run about 220 now that weather is cooling down and I am aware of a freeze out plug that loves to leak, and I will be fixing that whenever time arrives. (I will keep my antifreeze level under control for the time being) But my question is why does my thermo guage like to travel towards 260 when the car is turned off and supposed to be cooling down? Is this because there are hotspots or just the way the guage likes to function? Let me know thanks, just curious not worried.

 

Is this a stock gauge or an aftermarket mechanical one?

 

Any leak in a cooling system releases pressure. System pressure is what keeps the boiling point of the coolant high. A pressure leak makes the coolant start to cook at a lower temp, hence the increase in temperature. For every 1lb of system pressure the boiling point of the coolant rises about 3 degrees. When you shut off the car the temp will rise before it goes down, factor in a loss of pressure and thats where you problem lies.

 

Why does the temperature rise normally though?

 

The temp rises because the coolant is not transferring heat because the water pump is not circulating, and the cooling fans shut off. When this happens the coolant temp will rise for a short period of time then slowly start to drop. It's a perfectly normal event and poses no problem as long as the cooling system maintains pressure.

 

so is that what heat soak is?

 

I've only used heat soak on this board to describe why some cars won't start when hot, because the starter has absorbed heat from the headers. I guess you could use it to describe any other time that excess heat is absorbed by something. When your coolant temp raises after you turn the engine off it is caused by residual heat from combustion. This is why you don't race your engine to 5000 rpms and then just shut it off. It'll overheat because it has all of this built up heat but no way to cool it except for it to transfer to the rest of the engine, coolant, and oil.

 

Where do you think the heat normally goes?

 

It is called "heat transfer" and it one of the principles air conditioning uses. Heat always travels from the hotter material or souce to the colder one. The residual heat will slowly move from the engine and transfer through surrounding materials until the engine becomes the same temp as the ambient air.

 

Of course it does, I was just questioning the wording of what he said.

 

I've heard the term "heat soak" used a lot in reference to fuel injectors. After the engine is shut off and local temps rise from lack of cooling, as described previously, the gas remaining in the injector tips can get dried out and leave deposits. Older injectors were more likely to have problems from deposits than are newer types.