Thermostat for Tahoe

sox10

my Tahoe temp gauge just started moving the other day, only two notches on the gauge but i know this will lead to something. weird this is after a few minutes it goes right back to dead center.... could this be a stuck thermostat?

kiawah

Search the tahoe forums for defective gauges (stepper motors), there's a huge long thread on the topic. There are companies that will rebuild for you, substantially cheaper than a dealer repair..

sox10

i don't believe it is the gauge, i had mine replaced by Chevy for defective a speedometer

kiawah

Go back to the coolant basics.

Filled w/coolant, waterpump working, thermostat working, temperature sensor working.

sox10

filled with coolant =check
new thermostat= check
temp sensor?
maybe the waterpump?

just changed the thermostat....cranked it up got to 210 blew cold air...as soon as I started to drive off then heat was coming through..... could it be that the waterpump is starting to go?

swifty20

a bad gauge or relay of some sort?

kiawah

After you drain and refill, you need to go thru a couple cycles of warm up and cool down, to get all of the air purged out of the lines. When the engine is hot and running, turn on your front and back heaters so the heated coolant can flow thru the hoses and return any air back to the radiator where it is trapped. Then when the engine is cooled, it will draw out of the reservoir to refill the radiator. On the next heat up cycle, the coolant will expand and blow out the air into the reservoir, and then when cooled will draw more coolant back into the radiator. It will take a couple of these cycles to purge the air out of the system.

When water pumps go, they will usually leak, and if you don't see it leaking on the ground, then you would eventually notice that the reservoir is low and needs refilled. You don't mention loosing coolant.

If you still are having your gauge varying, then you may have a bad head gasket where the burnt gases, are leaking thru the gasket and into the cooling chambers. So instead of your radiator being completely full of coolant, you will always find air. These bubbles of air in the system, can cause blockages and swings in the gauges as the sensor detects the temperature of the air, followed by detecting temperature of the water. This problem can create higher than normal pressures in your cooling system, blowing hoses and radiators. It also allows coolant to leak into your cylinders and engine oil, potentially causing huge problems to cat converter and engine and bearings.