I didn’t do any of the work but I learned a lesson: when part of a pressurized system fails and is replaced the next weakest weakest part is likely to fail as well. This is why when a coolant hose is replaced the shop will usually replace all the hoses.


The story:

  • before Cars & Coffee last saturday morning the clutch pedal got stuck on the floor
  • picked it up off the floor, was able to drive the car but clutch felt soft
  • did some reasearch, sounds like the clutch master or slave cylinder
  • cheap part, messy job that requires a lift and bleeding the brake fluid system
  • on monday drove the car to Bavarian Motorsport, my independant shop of choice
  • they isolated it to the clutch slave cylinder which was leaking
  • they replaced it and i drove it to work
  • when i went to leave at 11PM the clutch pedal got stuck on the floor
  • i could pressurize the system by pumping the pedal but the clutch would slowly re-engage
  • sounds exactly like clutch master cylinder failure
  • master cylinder can have a leaking inner seal but not lose fluid because it’s a closed loop and fluid will be recycled
  • next morning call AAA (more on them later) and had the car towed back
  • everything seems fine, but it might be that the clutch master cylinder is failing
  • decide to have them replace it

Got the car back today and it’s working fine. Would have loved to do the work myself but I don’t have the facilities nad it’s probably for the better as it’s a messy job. The following diagram isn’t of an e30 but it does explain how the master cylinder and slave cylinder are connected:

  1. brake fluid reservior supplies the hyrdaulic fluid for the system
  2. the clutch master cylinder creates creates pressure when the clutch pedal is depressed
  3. ….
  4. ….
  5. The clutch slave cylinder is actuated by the pressure from the clutch master cylinder and physically engages the clutch


Here are the parts from the BMW service diagrams:


Oh yeah almost forgot about AAA. So they towed my car to the shop but because the e30’s oil pan is right over the front axles their truck scraped up my pristine oil pan. Kinda cheesed about it, but I guess it’s not that big a deal.


January 24, 2013 mechanical