Temperature gauge is bouncing, the car runs fine otherwise

JLYANT

MEMBER
1972 MERCURY COUGAR
81,000 MILES

The temp gauge goes to hot and goes up and down very quickly. I flushed the system and while it was flushing it remained cool. What causes this?

Monday, September 12th, 2011 AT 4:02 PM

3 Replies

JDL

MECHANIC
16,098 POSTS

Remove the thermostat, hook everything back-up, run the vehicle, does the temp gage stabilize?

How hot does it get?

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Monday, September 12th, 2011 AT 6:56 PM

JLYANT

MEMBER
3 POSTS

The system cooled down a bit after the flushing. It doesn't actually overheat now it just runs really hot. I will try the thermostat step. If that is successful what is the next step?

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Tuesday, September 13th, 2011 AT 2:57 PM

JDL

MECHANIC
16,098 POSTS

Maybe an issue with temp sending unit on engine or wiring circuit. I don't have a location for that sending unit. I don't have any wiring info for that gage or sending unit.

Possibly air trapped in the system? Radiator cap--water pump-- combustion gases getting into the coolant. Do you have a catch bottle connected to radiator? If the engine gets too hot, it will pop the cap, coolant either goes into the catch bottle or over-flow tube pointed at the ground.

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Tuesday, September 13th, 2011 AT 3:50 PM