chamilka

The radiator Expansion tank (white tank next to the windshield fluid tank) has two hoses coming out of it. One of the hoses starts from the expansion tank and goes on top right of the Radiator. This hose has a small device close to the expansion tank side, it is either “Expansion Tank Level Sensor” or “Expansion tank Pressure switch” I am not sure. This device is broken in my 89 S4 and Coolant was leaking trough it, I was able to remove it and connect a long hose between the expansion tank and radiator so I could drive it back home.
Now the questions:
1. What is this device? What is the purpose of it?
2. What are potential reasons for this device to fail? is this symptom of some other major problem that I don’t know of?
3. My radiator fans always come up the minute I start the car, could the device in question be responsible for that?
4. What other stuff should I replace when replacing this device?
5. I replaced the original hose (same size) with one I bough form Advance Auto Part, is this ok?

BTW I want to thank JP form Maryland for taking the time to help me out while I was stuck 6 hours away form home with a broken shark. We got some incredibly helpful people in this 928 forum.

Thank You
Chamilka

BC

Level sender is in the cap on the coolant tank

The valve in the small line is a pressure/volume release valve.

The Fan system has a few compexities, one of which is the way it runs the fans.

BC

The fans are told to come on at times of tempature, AC running, and if the intake manifold sensor (top of manifold) senses the intake is too hot.

Just as a side note - these cars run hot normally, so if its extra hot, you have very little if any headroom before something warps or breaks.

Mrmerlin

if when you turn on the key and the fans start check the connector at the front driver side of the radiator if this connection is off the fans will always run. You should be able to replace the pressure sensor its not to hard to do

David L. Lutz

I eliminated that device you are speaking of and have not had any issues.

Also I when I reinstalled my rad. I forgot to plug in the connector Mrmerlin refers to and my fans always ran. Pluged the connector in and all was back to normal.

chamilka

thanks all
Chamilka