[some_other_dave]

I noticed something interesting yesterday in my CRX.

I had to make a ~20 minute drive during the heat of the day. I have a full block in front of my radiator (but behind the bumper and AC condensor). It helps with warm-up more than aero, I think. The coolant temps were reading a little on the high end of "normal" on my stock gauge when I got near my freeway exit. I turned off the engine and went into EOC.

When I got to the end of my exit, I bump-started the car, and noticed that the coolant temp gauge read noticeably higher. By the time the engine had run for ~30 seconds or so, the temp had come down to lower than it had been on the freeway.

My guess about what happened to cause this:
I think that the radiator continued to drop the temperature of the coolant that was in it. Meanwhile, the presumably smaller amount of coolant that was in the (warm) engine got a chance to heat-soak in there, raising its temp. When I started the engine again, and the coolant circulated, the colder and warmer coolant got mixed together, bringing the overall temp down.

I am wondering if this heat soak effect could do anything bad to the engine while it is off, or when it just starts up again? I suppose you'd really want to avoid extended EOC in super frigid temperatures if your engine bay was really very well insulated (and your radiator not so), to avoid sudden massive temperature changes when can damage metal. But I think that's a really rare circumstance anyway.

-soD