Hey…how’s it going?
I have a quick question. I have a 1988 BMW 735i 5 speed manual. Two years ago, I installed a new Sachs clutch disc/pressure plate/throw out bearing/clutch master cylinder/slave cylinder. Because of so many new parts, of course there will be air in the system upon assembly. I used the reverse pressure bleed technique bleeding from the slave cylinder and allowing the air bubbles to take the natural upward path of travel. Everything went well, had no issues, clutch pedal was fine…maybe not as firm as some American manual transmission clutch pedals, but it worked well.
Fast forward two years. Now the brake
fluid in the reservoir is muddy and murky colored…time to flush the clutch system. This time I bled from up top since the system has no air in it to escape. I used a turkey baster to remove the majority of the dirty brake fluid from the reservoir. Then I topped it up with fresh fluid. I then attached the pressure bleeder to the reservoir (which is separate from the main brake system master cylinder reservoir). Pressure Bleeder instructions advise not to pressurize the system no more than 20 psi. I didn’t go above 12psi since it’s a small system and not really necessary to pump in 20 psi of pressure…IMHO.
I crawled underneath with my piece of hose and a catch bottle and attached the hose to the bleeder nipple on the slave cylinder, and stuck the end of it in the catch bottle. I used my 7mm wrench to crack open the bleeder about ¼ turn and let the fluid slowly start to flow. I allowed gravity and the 12 psi of pressure to work at it’s own pace. After seeing the fluid run out clear I go up inside of the car and pump the clutch pedal several times to assist with the old fluid evacuation. The pedal went all the way to the floor and I pulled it back up to it’s normal position each time with my hand and let the fluid continue to run a little bit more.
When I felt satisfied that it was done, I closed the bleeder valve on the slave cylinder. I went back up top and released the pressure on the pressure bleeder bottle. I removed any excess brake fluid from the reservoir until it was at the max normal fluid level line on the reservoir and capped it. I started the car up to drive it down off the ramps, and the pedal was a little soft, but it very quickly returned to normal pedal pressure and feel. It actually felt much more firm than it was before bleeding the system. That was a week ago. The very next day after the flush, I started noticing this noisy rubbing type of sound coming from the clutch disc whenever I lightly pressed the clutch pedal. When I release the pedal the noise goes away of course. When I pressed completely all the way into the pedal, the noise gets louder, and again goes away when I release the pedal. I never had that noise prior to the flush for the entire two years before.
I didn’t take anything apart to cause any clearance issues with the clutch disc and the flywheel. All that I can think of is maybe when I pressed the pedal several time during the bleeding, the extra pressure may have caused the pushrod inside the slave cylinder to move forward a little and put pressure against the clutch release lever inside of the bell housing. This could have caused a “pre-loaded” effect…maybe. I don’t know. I can’t imagine what the heck it could be other than that.
Any suggestions as to what I can check?