So when my daughter stop the car tonight, I turn the key back on (not starting the car), the temp needle go up to 3/4. I started the engine, rev it up to 5K a few times, the temp needle went back down to middle. What's going on? Is it really overheat?
If it was driven hard, parked quickly and shut off, heat will build and rise. It did not run long enough to pull the extra heat out of the engine. This would be normal.
If it was driven easy, allowed a little time to idle before this shut off and still had the temp go up you are looking at a problem.
Could be marginal cooling system, low on fluid as mentioned. The heat from driving has to go somewhere and it will always rise to the top.
Find out more before tearing things apart.
I agree with Westlotorn. It could be "heat soak"--residual heat in the block, with the coolant not circulating. Check the coolant level to make sure the red indicator pops up. If it's at the proper level, start it up and let it run for a while to see if the temperature is stable. If it's okay at idle, take it out for a short drive and keep an eye on the temperature. It might be fine. You can monitor the temperature on the digital display or using the gauge. If it climbs above 200 degrees F or the needle moves past the 12:00 position, shut it down immediately.
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