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Weird set of events on 85 635

Discussion in 'E24 (1977-1989)' started by SharkInfested, Jun 14, 2020.

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    Hi folks, hope all is well wherever you are!

    I’m writing to tap your brains to ask for some help in a very weird set of events on my 635csi (manual trans). I’ve had the car for 25 years and worked on her for as long.

    Bare with me on this long question/set of events.

    1. In July on a 50 mile stop and go trek in 100 degree weather, my brakes suddenly faded drastically. Pedal became very hard. Still drivable, but had to extend stopping distance until I arrived home.

    I thought it was the slave cylinder.

    2. Next, fast forward to yesterday. Just wanted to take her out on a short drive to stretch her legs. I noticed the odometer (main and trip) stopped working (118k on the clock).

    3. I started testing things: I noticed the cruise control stopped working (which worked brilliantly before).

    4. Also noticed the mpg gauge (on the tach dial) stopped working too (again worked brilliantly before). Tach still works. The mpg gauge will be all the way to the left at a stop, and as soon as I press the throttle, it goes all the way to the right and stays there until I fully release the throttle. Nothing in between, even when I try to maintain any speed.

    5. I also noticed, in a deceleration, that the speedometer jumped down from 65 to 60 immediately. No gradual reduction. Just a jump down.

    Before 3 above, I though I had two different problems. The slave cylinder and the odometer gears. But with 118k, I thought gears to be premature.

    After 5 above, I got a feeling that some of these issues can be interconnected.

    Possible a cable coming loose from the wheel measuring speed (and odo)? I think the brake problem is probably its own issue, but the other items are too weird to be dash cluster gear problems (I think).

    So I ask you, what do you think?


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