Problems bleeding a concentric clutch

seight · Post by **seight** » Sun Oct 28, 2007 10:27 am

I've got a T5 box on my rv8 and I'm having real problems bleeding the clutch. I'm using a Saab concentric slave and a std Girling master with built in reservoir.

Problem is that when I try to bleed the system no fluid returns from the slave to the master when I let off the pedal. As a result the slave just gets pushed further and further out until a seal pops. A leak under the bellhousing was how I spotted there was a problem.

My car is a Westfield Seight which already had the master cyl fitted by the factory. For some reason they left no adjustment on the slave push rod (chopped a lot off) when they connected it to the pedal. When I have the pedal level with the brake pedal I think the short pushrod means the port to the reservoir in the master cyl doesn't work properly. I think this means extra fluid is always taken from the reservoir during normal operation when the pedal comes up rather than the slave when the clutch pushes the bearing back.

Does all that make sense?

Anyone got any tips?

Should I try new pushrod / master cylinder and if so what's the best procedure for setting is all up.

thanks
Mike

(very frustrated)

stevieturbo · Post by **stevieturbo** » Sun Oct 28, 2007 10:48 am

All this, and not once do you mention a bleed nipple of any sorts ??

I know I seen a crappy hydraulic system on a peugeot once. As far as I could tell, there was no provision whatsoever for bleeding it. I can only assume that it was totally non-servicable. Which wouldnt surprise me with french shite.

I would hope Saab wouldnt do the same, nor any aftermarket place choose to use a system like that.

So where is the bleed nipple ?

seight · Post by **seight** » Sun Oct 28, 2007 11:05 am

Good point - bleed nipple is on the slave (well on the end of a hose that is connected to the slave).

Clutch appears to bleed ok and I get all the bubbles out but when I close the nipple and start trying the clutch is when the slave starts to get 'pumped' up. Didn't know this was happenning to start with as it's all hidden inside the bellhousing.

This thing is driving me mad but at least I know what part of the problem is now - just not too sure how to solve it.

thanks
Mike

stevieturbo · Post by **stevieturbo** » Sun Oct 28, 2007 11:09 am

Is your pedal adjusted right ?

If the pedal wasnt coming back far enough to expose the hole to the reservoir enough, it could give the symptoms you describe.

Or there may simply be a slave issue

seight · Post by **seight** » Sun Oct 28, 2007 5:25 pm

My type of master cyl is called a "moving seal with axial compensating port" which has the port to the master cyl in the end of the bore.

When you press the pedal the pushrod it relieves pressure on an internal "pull rod" which then allows a seal to shut off the reservoir. Then as the push rod moves down the bore it forces fluid out of a side port to the slave.

I have a feeling that because my master was installed with the max amount chopped off the push rod thread then the internal pull rod opens the reservoir port bofore it should - hence fluid is drawn from there before the slave.

The pedal is adjusted (as much as poss with the short push rod) to be level with the brake and it stops against a chassis member (which is normal).

I fitted an adjustable stop for downward movement to stop overstroking the slave but even when that is set to allow minimal movement I still pump up the slave.

I did have a link to a cross section diagram in a 'google book' but they've changed the pages that are available in preview mode so it's dissappeared.

Sorry it's long winded but the design of master is a bit different from 'normal'. I can see it would be easy with a more 'normal' master where the plunger seals move past the inlet and outlet ports.

Do you think I could be right about the shortened pushrod causing problems with the end seal to the reservoir?

Mike

ian.stewart · Post by **ian.stewart** » Sun Oct 28, 2007 5:48 pm

I think the old addage KISS may well apply here, I would be reverting back to a basic simple type master cyl.

stevieturbo · Post by **stevieturbo** » Sun Oct 28, 2007 6:02 pm

Havent a clue.....

seight · Post by **seight** » Sun Oct 28, 2007 6:59 pm

ian.stewart wrote:I think the old addage KISS may well apply here, I would be reverting back to a basic simple type master cyl.

I fear you may be right - but the master cyl I've got is the std one that Westfield supply with their V8 kits and works with other more std slaves. They fitted it and left no pushrod for me to adjust to see if I'm right about what is causing the problem.

I'll have a look round for other 'short' masters - can't have the outlet on the end as it would be up against the rocker cover.

Mike

ian.stewart · Post by **ian.stewart** » Sun Oct 28, 2007 7:14 pm

I have clearance problems with my Master cyl, in the end I milled off about 10mm from the rocker side of the cylinder,, this would be obviously. or even dependent of the bore of the cyl as to how much you can remove
the other options could be , reverse the cylinder , lengthen the top of the pedal and mount the cylinder inboard and above the pivot point of the pedal, or if space is a real problem operate the master cyl via a bell crank and mount it where you desire,
you might get some ideas here. http://www.rallydesign.co.uk/catalog/in ... th=562_582

seight · Post by **seight** » Sun Oct 28, 2007 7:49 pm

Well at Rally Designs prices for those Wilwood integral master cyls I may just try one of those and see what happens. wilwood.com has all the measurements too so I'll check them out.
thanks
Mike