Clutch not bleeding !! Aaaargh!!!

[seight]

I am starting to despair of my clutch!

When I try to bleed it the fluid is not returning to the master cylinder properly. This means repeated pressing the pedal just pumps more fluid to the slave and blows the o-rings.

Is there a proper way to set up a master cyl pushrod? Adjusting it to the max in either direction seems to have more or less the same result.

The master is a Girling integral reservoir item, I found this site that describes how they work (under the heading Non-residual Pressure Master Cylinder (Girling)): http://www.the-crankshaft.info/2009/09/ ... ystem.html

Could the internal valve in the master be playing up? Meaning the inlet port opens too early and therefore fluid is pulled from the reservoir instead of the slave when the pedal comes back up?

Should I have -3 or -4 lines to the slave? Does that really matter?

I'm using a .7" bore master with a Saab concentric slave and -3 lines.

Any ideas appreciated as always.

thanks
Mike

[unstable load]

Try to "reverse bleed it" by usng a big syringe filled with fluid from the slave end to the master. Remember to drain the master a bit to allow for the fluid coming up.

Worth a try, methinks.

[seight]

I might have sussed it out - in theory at least. I think the master cyl plunger is not coming all the way back out when the pedal is up as far as it will go. I think this means the valve at the end of the bore is not opening correctly and therefore not allowing the pressure to equalise and as a result more and more fluid is going to the slave with every push on the pedal.

I'll try spacing the master cyl away from the pedal in the morning so the push rod can reach full outward travel. Then I just need to fit a pedal stop to prevent too much inward travel when pressed.

Bit annoying this as the pedal box is supposed to be designed for this master cylinder. Maybe the push rods have altered and the screw thread doesn't go as far as it used to.

Fingers crossed.

Mike

[Darkspeed]

I was going to ask if you had a tension spring fitted to the clutch keeping pressure on the piston - or if the push rod was too long preventing the cylinder returning which prevents the non return valve from opening.

Shortening the M/C push rod or spacing should solve it

Andrew

[DEVONMAN]

Hi Seight.
Are you saying that the clutch is staying released when you take your foot off the pedal?

If so, then you may want to ignore the following.

If the clutch release bearing has the correct initial clearance, then the o rings should not pop out. If they do then the slave cylinder is moving too much. The clutch diaphragm should force the slave cylinder back.

If the initial release bearing clearance is correct and the O rings have popped then most probably the diaphragm will now be damages due to excessive over centre movement.
Regards Denis

[stevieturbo]

I might have sussed it out - in theory at least. I think the master cyl plunger is not coming all the way back out when the pedal is up as far as it will go. I think this means the valve at the end of the bore is not opening correctly and therefore not allowing the pressure to equalise and as a result more and more fluid is going to the slave with every push on the pedal.

I'll try spacing the master cyl away from the pedal in the morning so the push rod can reach full outward travel. Then I just need to fit a pedal stop to prevent too much inward travel when pressed.

Bit annoying this as the pedal box is supposed to be designed for this master cylinder. Maybe the push rods have altered and the screw thread doesn't go as far as it used to.

Fingers crossed.

Mike

very possible.

It can be like that, yet the clutch still appear to work properly.

[DEVONMAN]

Hi again.
On the Girling master cylinder, there is NO valve to prevent the fluid returing from the slave cylinder.
The valve at the end of the cylinder just lets more new fluid into the master cylinder when the pedal is fully returned.
Cheers Denis

[stevieturbo]

If the pedal is fully returned is the issue...

[seight]

OK, spaced the master cyl from the pedal and it seems to work. Trouble is the built in reservoir then hits my tandem brake pedal banjo fittings. There's not enough thread left on the push rod to avoid spacing it so it's either a slightly different master or some other kind of fitting to the pedal. One step forward and all that.
Mike

[stevieturbo]

adapt and overcome. Just add more threads then and cut some off. Or cut/weld etc

[Darkspeed]

I had a similar issue and managed to get it sorted with running a Die down the push rod a bit further and shortening it.

Andrew