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Clutch slave Cylinder HELP

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tekspeek

Freshman Member
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I just rebuilt my Clutch Master and Slave Cylinders and am trying to bleed them. I first tried the standard method of putting a tube from the bleeder valve into a jar with some brake fluid, pump the clutch and open the bleeder valve. Nothing. I got a little bit of brake fluid out but mostly air.

I gave this up and have been trying to bleed them with a MightyVac. (This is basically a vacuum pump hooked up to the bleeder valve and you suck the brake fluid into a small bottle) With MightVac I get brake fluid and air. Constant bubbles.

I have processed at least 8 complete refills of the Master Cylinder and I never get un-bubbled brake fluid.

At this point I have about 2 inches of clutch movement so I can shift but after driving for a bit I have to pump up the clutch to get it to work.

Any ideas? (I have already verified by dissassembling and checking that I have rubber parts in the proper orientation.

Thanks,
Pete
 
i've never been able to get a good bleed with a mightyvac. Maybe the clutch hose is crimped or not sealing well?
 
I would try the obvious. Look for leaks. In a pressurized
hydraulic loop, Air in = fluid out, usually.

Fill everything up again, bleed again, run engine in place
and push pedals, dry shift a few times, turn off engine and
look beneath for oil leaks.

Tinster in Puerto Rico
 
Hi,

I also would suspect a leak.

Another possible cause of a leak is if the wrong size seal was used in the MC or SC? There were different bores, it's important to use the right size. Some rebuild kits even come with extras, in the various sizes, which makes it easy to pick the wrong one.

I also have had little luck bleeding hydraulics with a Mityvac (useful for many other things, though).

Best method for me is still with an assistant *slowly* pumping the brake pedal and Speed Bleeders on the various fittings. (Speed Bleeders do make possible to do as a one-person job, but I get tired of crawling under/climbing out from under the car!)

Another common source of the leak is the bleeder screws themselves, along their threads. I like to use a little Locktite thread sealant on there. I have also used Teflon "plumbers" tape on the threads in the past, very carefully though... you don't want any pieces of that stuff floating around in a hydraulic system!

Finally, I seem to have about 50% luck rebuilding old MCs and SCs. Seems some of the time the bores just can't be honed well enough to seal well, or have been over-honed in the past. The only solution then is to replace the MC or SC, or have it sleeved (www.applehyadraulics.com). Cheaper/available parts - like common rear brake SCs - I haven't even tried to rebuild lately, just replace with new as a matter of course.

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