No clutch pressure (91 318i)

[fleece johnson]

I searched and checked the first few pages of this subsection but found nothing.

So, I was just on my way home from work and out of nowhere I lost all clutch pressure.  It happened when I stopped at a stop sign and then went to put it into first gear and engage the clutch.  The pedal went all the way to the floor and I couldn't get it into first gear without grinding the hell out of it.  I thought I noticed a change in pressure about a week ago (it would engage closer off of the floor then normal) but everything still worked without grinding so I assumed I was imagining it.  Back to this evening, I had to sort of time the RPMs and slip it into second to start out and then just finesse it from gear to gear without using the clutch.  Now here's where it gets a little weird.  Once I made it to the expressway and was cruising in 5th gear for a while, I gave the clutch a little push and pressure was back again.  It didn't feel 100%, but I could change gears without grinding at all.

Cliffs notes - intermittent clutch pressure issues.

Any ideas?


Thanks,
Brian

[Boosted E30]

either you have a leak in your clutch master cylinder which is attached directly to the pedal or your clutch slave cylinder is leaking which is bolted to the transmission and opperates the clutch fork.

Do you have any fluid on the carpet inside by the clutch pedal??? if so replace the master cylinder.

If you cant see any leaks from either cylinder and you have enough fluid in the container i would replace both cylinders and bleed properly and you should have no more problems.

[DesktopDave]

I'd guess a bad slave cylinder.  Check the front half of the reservoir for correct fluid level first, then check the little blue hose that runs off the side and the clutch lines for leaks.  Take a good look at the master cylinder for leaks too - it's between the clutch and brake pedals.  The slave sits on the driver's side of the transmission.

RealOEM diagram:
http://www.realoem.com/bmw/showparts.do?model=AJ93&mospid=47318&btnr=21_0004&hg=21&fg=10

If the fluid level is correct and no leaks then it's most likely a bad slave.

I had to replace mine at about 110k miles.  It's not a really hard job on the e30 but I had to bleed it twice to be sure it was right.  Haven't done a master cylinder yet, that looks like a bit of fun...

[Wizard]

I'd guess a bad slave cylinder.

+1

Had to do this on mine a year or so ago. Not a real bad job to do....

[fleece johnson]

No fluid inside by the clutch pedal.  Sounds like the slave cylinder.  I'll take a closer look this weekend.  The weird thing is I drove the 40 miles to work this morning with no problems whatsoever.  I appreciate the helpful responses.

[DesktopDave]

Let us know how it went...keep in mind that the only thing pushing your clutch (or brakes) is a pair of little rubber washers.  They can re-seal temporarily when they heat up or when the actuator moves, or when the grit and water are pushed around.  I've seen caliper seals that were held together only by 30 years of grit and corrosion...they still worked (sort of...) and didn't leak.

I'd also consider a slave cylinder and hoses a wear item with a limited lifespan.  I can't afford to replace everything at once, but as I work my way around the car I've been replacing every little bit of rubber that I can get to.

I'm always surprised by what I find in hydraulic systems...but they're almost magically simple and reliable.  Much easier to troubleshoot than electrical systems, that's for sure.

[fleece johnson]

So, I got the replacement slave cylinder yesterday (Pelican Parts, $30) and switched it out with the old one, which looked like it was probably the original 18 year old unit.  Now I'm trying to figure out how to bleed the clutch.  Not easy.  Pump the clutch a bunch of times, hold clutch down, open bleeder valve, close bleeder valve, repeat.  No pressure.  I'll have another look after work and see what I can figure out.

Thanks again for the help.