I was in the middle of a brake fluid flush and thought that my pressure bleeder would be appropriate to bleed the clutch slave....

Well that is what one would think....but....last night I had done the brakes 1x around and had the pressure bleeder (PB) still attached. I loosened the slave bleeder and got a little fluid then PHSSSST alot of air. I shut it down, checked PB & resevoir for sufficient fluid (both OK) and then tried to let more fluid out - MORE AIR! Clutch pedal had no resistance. So I then compressed the slave (per Bentley manual for slave replacement) via some wood shims and pressure bled again - no luck. At that point I tried the reverse bleed (I had a new, unused East German pin oiler around - don't ask) and got it to eventually work and get the air out. Pulled out my shims and had pedal with a little more free play than specc'd. A few more pumps and we were back in business.

All this to say that it is a tricky system to bleed - I would'v'e thought that the PB would work - maybe I opened it up too fast - who knows (the master draw is in the back section of the resevoir).

Be warned - leave some time and some extra fluid for this 'just in case'.

Derek

Anybody else got some insight, methods, comments, imrpovements?

 

You have to keep the reservoir more than 3/4 full before bleeding the clutch. The fluid line that goes from the brake master cylinder reservoir to the clutch master cylinder connects at roughly the mid point (at the seam in the plastic tank). Should the fluid drop below this point, air can get into the cylinder. In fact, by the time your brake pads are at their end of life without any topping up of fluid, the fluid level will be close to the pickoff point for the clutch. This does not usually cause any problems, since the line connecting the clutch cylinder acts as enough of a reservoir. Most pressure bleeders are designed to leave a certain amount of air space above the fluid during operation so as to not overfill the reservoir.

The reason why the clutch does not tap off of the reservoir at a lower point is to reserve enough fluid for the brakes in case of clutch system leaks.

 

Well to be honest I recall the resevoir topped up pretty full at that point.

My bleeder has a slight air leak at the pressure gauge, so even if I suck out as much of the brake fluid as possible out of the resevoir, by the time I've gone round 1x on the brakes, alot of the air has 'escaped' though the leak - only to be replaced with brake fluid.

Anyhoo, if I'm reading you correctly, you are writing that if the fluid is high enough, I should be able to use a pressure bleeder and bleed the slave w/o any other work (compressing slave etc.) - correct?

Thanks

Derek

 

When I did my brakes/clutch I used the old "Down-Hold It-Up" method for both brakes & clutch w/o any problems. Did take quite a few cycles with clutch as not much movement so only a small amount of fluid comes out each time you crack the bleed screw.