I have a 96 VW Jetta GL. 2.0L I can't figure out why it is over heating. I have changed the water pump, thermostat and all the lines. The temp in fine as long as it's running but as soon as I start driving it the temp goes up.

 

It could be the temp. sensor. Is the check engine light on??

 

no it is not on.

 

I had the same problem, i found out that the coolent wasn't going through the cooling system so i squeezed the rubber coolent hose and it finally worked itself throughout then i had to add more coolent, so that meant there was air pockets in the cooling system.

 

Thank you. I'll give it a shot and see what happens.