<E30> Replaced clutch master cylinder

[Michiel van Wessem <jmvw@xxxxxxxxx>]

Hi.

Tuesday, on my way home, the clutch started to engage while I had the pedal
down. Also, the clutch pedal wouldn't come up much anymore. At first, I
could lift the pedal up by putting my foot under the pedal and the clutch
would disengage long enough to shift quickly if I pressed it down quickly,
but I had to be quick because the clutch would engage all by itself while I
had the pedal down. Soon enough, it became so bad, I couldn't shift anymore.

I rented a Ford Aspire to get to work the next two days. That car felt like
it was out of alignment and had a bent rim and once I lowered the 70+ PSI
pressure in the left front tire that tire decided to give up all air on the
NJ Turnpike, but I digress.

First I thought the culprit was the "compression spring" under the clutch
pedal. I thought it didnt' push the pedal back up like it was supposed to.
After messing around with it I decided that it was impossible that this
thing would ever push the pedal up from the floorboard - it will only work
when the pedal is almost up. Surely the pressure from the clutch trowout
lever, tranmitted back up through the clutch hydraulics has to push it up
the first bit.

The more I thought (I didn't sleep much the first night) about how the
clutch would disengage if you pressed the pedal down quickly and then it
would engage again by itself, the more hydraulic this seemed. 

I hadn't seen any brake fluid anywhere, so that gave me a clue. The next
evening, I tried out this:

I had my wife hold down the clutch pedal while I removed the slave cylinder
from the transmission. I wanted to see if I could push the piston in. I'm
kind of smug about this: if it would push in, no matter how slowly, the
master cylinder had to be faulty. Because I hadn't seen brake fluid, the
fluid had to be leaking back up towards the brake fluid reservoir. 

Indeed I could slowly push in the piston. The next day I bought a new
master cylinder (fortunately, a dealer had this in stock; the dealer was
expensive, but renting a car was more expensive). 

I installed the new cylinder the same evening and that fixed it!! 

Driving this car after the Ford Aspire, I understand better how nice my car
really is; how good the handling is and how quiet it is. Maybe I'll even
give the drivers of those really small cars a little more leeway.

Notes:

- - I broke the pedal's "compression spring", but even without that thing the
clutch works fine. It's just that sometimes the cruise control switches off
because the pedal isn't pushing against the clutch switch hard enough. I'll
replace it when I get a new one in a few days.

- - This problem was not in the clutch troubleshooting table at
http://www.bmwe30.net/, but the fact that the dealer had that master
cylinder in stock might indicate that it's a common problem.

- - I wanted to bleed the clutch, but the bleeder opening on the clutch slave
cylinder didn't let anything through. Still, the clutch works fine. My
conclusion is that it doesn't matter at all if there's some air in the
clutch hydraulic system - the forces aren't anywhere near that of brakes.
The only reason I see for bleeding the clutch every now and then is to get
any possible debris out of the lines.

Anybody really read this? Well, thank you!

Michiel (325es <http://www.monmouth.com/~jmvw/cars/BMW> )
- ----------------
>From Jackson, NJ

  e-mail at night: jmvw@domain.elided
 e-mail while day: jmvw@domain.elided

------------------------------