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My temperature gauge turned into a little seismograph a few days ago. I was driving through mountainous roads in WV and Maryland, temperatures near 100, AC blasting, highways speed, and the temperature gauge starts bouncing all over the place. Actually, it never went above it's normal setpoint, but it would bounce around the lower end like crazy. Driving on flat land the last couple of days and everything is normal. I'm thinking there was air in the system that was being measured instead of coolant, but I'm not sure why the extreme demands of that day would cause this. Coolant level is full. Any thoughts as to why, and anything to be concerned about?
Ck your coolant level in the rad not the over flow bottle asap and dead cold........ If that's full, ck the wire connector on the sender. You just may be correct and the unit will not measure air temp, which if it did would show colder.
Ck your coolant level in the rad not the over flow bottle asap and dead cold........ If that's full, ck the wire connector on the sender. You just may be correct and the unit will not measure air temp, which if it did would show colder.
Agree with you. I have a Suzuki Sidekick that did the same as the OP's. The cure was to replace the wire terminal that connects to the temperature sending unit near the thermostat housing. The terminal did not close over the connection point at the sender tight enough (it was loose).
But if for whatever reason the antifreeze fails to make full contact with the temperature gage's sending unit, the temperature drops off. Then it comes up when the hot antifreeze touches the sender once again. So, I would check the antifreeze level first, and make sure that there is no air in the system. A lot of cars have an antifreeze bleed port. The one on my Civic is next to the thermostat housing, and is used to remove all traces of air from the antifreeze.
Mitch is really right. Always start with year make and model.
He is thinking poor ground to the engine maybe as well as a voltage limiter that works the temp and fuel gauges, which on many cars are tied in electricly speaking.
I simply picked the 2 most likey problems.
And yup lots of cars and bikes too have bleeders on the cooling system somewhere. If there has been a loss, and air somehow has entered the system the over flow return bottle may not work at all. It takes a solid liquid for the system to work.
If you mean abrupt changes then loose wires, etc. seem a likely explanation. If you mean a steady rise followed by a steady drop, correlated with load on the engine...then that's what's really happening.
AC in the mountains on a hot day is a near worst-case for overheating. The only thing worse is pulling a trailer at the same time.
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