1997 Chevy Monte Carlo Temperature gauge cycles to overheat

MAXLAMBERT01

MEMBER
1997 CHEVROLET MONTE CARLO
6 CYL
FWD
AUTOMATIC
97,500 MILES

My car is a 1997 Chevy Monte Carlo Z34. It's developed this problem where, after 15 minutes of operation, the temperature needle moves from its normal temperature over to overheat, causing the red light to turn on. It stays there for a few seconds, not more than 15-30 sec, then falls back down to normal. It stays normal for a few miinutes, then the cycle repeats again. This happens over an over. I've had the car to the dealer and they've changed out the thermostat and checked the car on their machines and they claim the car is operating at the correct temperature all the time and the fault is in the gauge itself.

I don't understand how this can be true. I'm thinking about putting in an aftermarket temperature gauge and seeing if it verifies what they're saying.

Are there any conditions that can cause this kind of behavior?

2 Replies

TEAG

MEMBER
158 POSTS

Did the dealership check the fan? If your fan switch is engaging whenever it feels like it, that could give you the temp readings you described. Is there any sign of overheating besides the gauge? Any bubbling/boiling or loss of coolant? You should pop the hood and watch the fan. If the fan goes on and off in sync with the temp gauge, the problems the fan switch. If the problem is in the reading, Its most likely the coolant temperature sending unit. To check this you should disconect the electrical connector to the sending unit. If I recall correctly, its located right under the thermostat housing. Now take a jumper wire and connect it to the dark green wire terminal in the harness connector. Connect the other end of the jumper wire to a good ground. Turn the ignition to the run position (do not start). If the gauge goes full up, the circuit and gauge are ok. If the gauge works and the fan works, the problem is most likely the sending unit. They easy to replace and fairly cheap at your local parts store. Hope this helps ya out. Feel free to hit me back for more?'S or feedback. Good luck! :)

Teag