Heat won't work when car moves

[minikin84]

I have no idea what type of heater this car has. It is a 1998 Plymouth Breeze. Nothing special, all manual windows and locks. Automatic trans. AC works great.

If you go outside and start the car and let it sit for a while, the heat will work fine, and the temperature guage sits at a normal operating temperature. As soon as you start driving, the temp guage drops back down into the blue and the heater starts spewing ice cold air, no matter what position the exterior vent is in. When you turn the vent dial, it makes an audible noise so I don't think that it is suck open, but I've never looked.. as I have no idea where to find it. And information would be greatly appreciated. Thanks in advance.

[typesix]

If temp gauge drops back down into cold area when the car is moving, most likely need a new thermostat.

[danielsatur]

If car is running to cold, because of winter, put a piece of card board in front of the radiator.

Is your coolant fan running?
How old is your thermostat?

[minikin84]

The fan runs fine. The thermostat is at least 3 years old, that is how long we have had the car.

I believe we found what could be the problem.. the "coolant" literally looks like mud. Could that be the problem? Does that mean we have a leaky head gasket? We constantly have to put oil in this car, but we thought it was just burning it.

[LordZarkon]

You have a blown head gasket. Ouch. $$$$$$$