Hi! My 2005 Impala is overheating , sometimes, and only for a minute.
(When it goes into the red, I pull over and turn car off for a few minutes.) The needle fluctuates, though.
I read old posts, but my mechanic tried them. Here’s what’s gone on so far:
Replaced thermostat, flushed / refilled antifreeze , car worked fine for a day, then it started again. He then took an air pocket out. He took it for a drive, it was fine. I drove it for a day, it was fine. The next day it started up again (needle quickly fluctuating, sometimes needle slowly fluctuating).
He replaced the upper radiator hose. He then drove the car (local and on highway) for 2 1/2 hours, it was fine. I picked it up and it was perfect for the rest of the day/evening. This morning, after driving about 8 miles, it started again. I’m dropping it off tonight. He said it is hard to know exactly what it is without trying things. He said next he would try water pump or radiator.
Any thoughts/help/ideas are appreciated. Thank you!
Btw, this mechanic was referred to me 20 years ago, and he’s always been very good to me, so I don’t think he’s trying to screw me. Thanks!

is the car overheating or not maybe you have a problem with the temp. gauge or the wiring or the sending unit? also try a new rad. cap

I wouldn’t go with a pump or radiator yet, those wouldn’t seem to cause intermittent overheat like you’re seeing. Like Big Marc said, it could be a sensor/gauge issue. But putting on a new (factory) cap would be a cheap thing to do.

It could also be air trapped in the system.

Are you losing any coolant! Engine compartment is dry? No visible coolant leaks anywhere?

Does your car have a radiator cap or is it one with the pressure cap on a remote coolant tank? If you have a radiator cap, check the level in the radiator in the morning before driving. If it is not full, you are losing coolant and have to find out where. Next, when it is overheating, make sure the a/c and defroster settings are off and open the hood and you should have a radiator fan running. If not, tell your mechanic.

And has a cooling system pressure test been done? Lots to check before throwing (very expensive) parts at it.

You guys ROCK!!
Thank you sooooooo much!!!