BMW Blog

I just bought a 94 325 and i am having some probs. This is my first Bimmer, and I have never worked on one before. I noticed that my heater doesnt blow hot air. I tried everything, bleeding the cooling system as the board here stated.

This is what she does: Whenever the car is not moving, she gets to operating temp (12 o'clock postition). But the heater still doesnt blow hot air. Everything else works fine, AC and the blower... it just doesnt get hot when you turn the temp control (below the center vent) to red.

BUT---- whenever I get the car to highway speeds the temp indicator drops all the way back down to the blue. If I keep it at highway speed, she runs cold all the time (in the blue)... but if I stop for a while the temp goes back to normal and doesnt get any hotter that 12 o'clock. but as soon as I drive at speed... boom gets back down in the blue. All the while the heater never gets hot.

Could this be the thermostat sticking open? or something more sinister. Any suggestions?

Sounds like a stuck stat. Change it out. You may also want to consider changing the water pump since you're right there and if there are any questions as to whether the plastic impeller pump has been replaced (it likely has, but YNK). I believe your 94 has the metal housing already, but if not now's a good time to change.