2002 Pontiac Grand Prix cooling problems

CHOLLAR21

MEMBER
2002 PONTIAC GRAND PRIX
6 CYL
2WD
AUTOMATIC
177,000 MILES

My temp gauge fluctuates. It goes from overheating to back to normal. I have replaced my water pump, thermostat (195 degree), upper and lower radiator and heater hoses, and bypass hose. I have had the system flushed out a few times. I have bled the system out several times but still cant seem to get all the air out. I can drive the car about 30 minutes and then it spikes and then will drop. When it spikes I have no heat. I dont notice any leaks externally. I know that gm is famous for the lower intake gaskets being faulty. I also noticed after filling the radiator and then bleeding it and driving it for a little while it never spiked but I let the car cool and noticed the fluid was low in the radiator. I was wondering if you had any insight. The engine is a 3.1l.

3 Replies

JNOVACK

MECHANIC
723 POSTS

Test the temp sensor it sounds like the sensor is working intermitently
Testing

Temperature Gauge Inoperative Or Inaccurate

Disconnect the engine coolant temperature (gauge) sensor (usually a dark green wire).
Insert a 44 ohm resistor between the connector and ground.
Turn the ignition switch to the ON position. Does the gauge now read high, approximately 260 °F (127 °C)?
If the gauge now reads high, check for a poor connection. If okay, replace the gauge sensor.
If the gauge shows no change, check for a bad connection at the instrument cluster, or a short to voltage between the instrument cluster connector and the gauge sensor. If these circuits are okay, it may be necessary to service the instrument cluster.

Locate the engine coolant temperature gauge sensor. It is usually below the coolant connection, just below the bleeder connection.
Partially drain the cooling system to a level below the sensor.
Unplug the electrical connector.
Unscrew the sensor from the engine.
To install:

Thread the sensor into the engine. Use care not to damage the "pigtail" wire.
Reconnect the lead wire.
Refill the cooling system with the proper mix of DEX-COOL � and water and properly bleed the cooling system.
Check for leaks.