Thermostat and/or Fan clutch

[sparticus]

Once the engine warms up and the thermostat opens shouldn't the level in the expansion tank drop??
Using the newspaper test does the fan slow down gradually means the clutch is OK??

I've got a 91 318is and just flushed the system? As I run it wth cap off I never see the coolant level drop. I don't see any airbubbles so I think their all out of the system. Temp goes to 3/4 mark now.......

[///M42 sport]

Thats kinda high. The temp is supposed to be 1/2. Above 3/4, the auxiallary fan, inbetween the bumper and radiator is supposed to turn on as a safety. If not check the switch attached on the opposite side of the radiator cap. I also hoped you used BMW coolant, b/c anything else that contains phosphorous will degrade the aluminum fins in the radiator.

You should run it with the cap off until you start to see bubbleling. Immediately cap it and turn your blower on 4 in high heat. (I think)

Did you change the thermostat also?

If the fan slows down, then the clutch is slipping.
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Vermont Dispensary

[sparticus]

No didn't change the thermostat. I only see the electric fan go on when I turn the A/C on? I think I need to change the thermostat then........

[e30Matt]

That sounds more like the temp. controlled fan switch. Try replacing it, they're not all that expensive.