Roaming Temperature Gauge

[dlongnecker]

On my 1998 Montana, the temperature gauge roams all over the place. Often going into the red line. When the temperature gauge is on the upswing, cold air blows out of the heater. When it is on the down swing, warm air blows out.

If I turn the heater off, the temperature gauge still roams back and forth.

My first thought was the thermostat, so I brought it into the dealership to have it repaired. THe diagnosed it as a bad rear seal causing the oil/water to mix (the water looked fine to me).

After they did the repairs, I picked up the van and the temperature gauge still is going crazy. Exact same symptoms.

They then replaced the waterpump. WHen I picked up the car, same symptoms.

They then flushed out all the lines. When I picked up the car, same symptoms.

THey then replaced the thermostat again. When I picked up the car, same symptoms.

THe only reason why I can think of for the temperature gauge to flop around AND for the heater to blow cold is the thermostat not working. Any other ideas?

[cdru]

Your symptoms sound like an air bubble trapped in the cooling system. This can be caused by low coolant, head gasket or intake manifold leak, or improperly bled lines. When the gauge rises quickly or you get a blast of cold air, that is when the air bubble is at either the sensor or in the heater core.

[dbudworth]

dlongnecker did you ever figure out what was wrong with your van. We are having the same situation with our van. I think we took it a bit too far though. I filled the coolant back up, and now it is really leaking out the back end of the motor by the belt. Trying to decide if it is a bad intake valve or a bad head gasket. Also when I tried driving it again after refilling it back up with coolant, blue smoke was pouring out the tailpipe. Leaving me to believe it is the head gasket. But the oil and cap look fine to me, no greyish gunk in there.

[cdru]

Blue smoke is burning oil. I'd be suspect of a cracked head or a head gasket. A failed head gasket may not contaminate the oil. If it fails to the outside or into a cylinder, it never would mix with oil.