truck gets hot after shutting off

[BarryC]

Today, 2 or 3 times, I noticed when starting up the engine in my truck, after just a couple minutes being off, that the temperature gauge was showing a higher than normal temp., just momentarily. It's as if it got hot after shutting it off, and then when I started it, it ran at a normal temp. Anyone know why this would be? It never runs hot, but it does this from time to time.
In fact in the last year or so I've replaced the radiator and the heater core, and probably the thermostat. The radiator was leaking and had to be replaced, and then later on the heater core did too.
If you haven't seen my truck, it's an `87 F-150 with 5.8L HO.
I was checking on some Pine Barrens plant sites today.
Barry

 

[Ben Ruset]

The temp of the coolant will rise from the heat radiated within the engine. As the coolant is not flowing when you shut your truck off, it will get hotter as the heat is transfered from the engine to the coolant. When you start your truck, the hot coolant flows to the radiator where it's cooled off.

At least that's what my theory is. My old Jetta and both Corrados would cycle coolant through the engine and run the radiator fans for a while after you shut them off if it was hot enough.

 

[BarryC]

Hmmm..... Makes sense to me. I remember in years past, that it would boil over, out of the lid of the coolant recovery tank, after shutting off sometimes. I don't think it does that anymore.

The temp of the coolant will rise from the heat radiated within the engine. As the coolant is not flowing when you shut your truck off, it will get hotter as the heat is transfered from the engine to the coolant. When you start your truck, the hot coolant flows to the radiator where it's cooled off.

At least that's what my theory is. My old Jetta and both Corrados would cycle coolant through the engine and run the radiator fans for a while after you shut them off if it was hot enough.

 

[Ben Ruset]

The other thing is maybe you have air in the system somewhere.