|
I've studied this phenomenon on my Scangauge. It's really not much of a suprise. My coolant temperature sensor records the temp at a single point in the water jacket in my intake manifold. That temperature is about 195F. Meanwhile, the normal operating temp of my cylinder lining is probably a few hundred degrees warmer.
When coolant is flowing, the coolant keeps things steady-state, but when you switch off the engine, the water pump stops. Heat from the engine is conducted into the coolant temp sensor, so it reads hotter. But while the engine is off, heat is lost overall (just not at the temp sensor). Once the coolant has a few seconds to equalize the temperatures again, the sensor reads lower.
To switch off the water pump is to subject the car to another cycle of thermal expansion and contraction, just like what happens when you park the car. I wouldn't worry too much about it.
|