Clutch cylinder bleeding

[Tempest 0]

In order to further investigate the funny and annoying squeal on my US-G60 Rado, and because the weather was pleasant today, I decided to bleed the clutch cylinders.

 

Starting with the master cylinder, I opened up the valve, pressed the clutch pedal, and immediately noticed how the pedal stayed down :x

 

OK, brake fluid did come out of the valve, so by hand I operated the clutch pedal a few more times, and with the pedal down, I closed the bleeder valve again. A few presses on the pedal later and enough resistance was there again to make the pedal return by itself, although it was softer than before I started the bleeding process.

 

There was no noticable difference in fluid level in the reservoir :x

 

OK, on with the slave cylinder, same thing again: Open the valve, press the pedal, it stayed down. Operated the pedal by hand a few times, fluid came out of the valve, with pedal down closed the valve again. Again, after a few more hand-operations of the clutch pedal it decided to stay up again. Pushing the pedal was noticably softer than at the beginning of this entire excercise.

 

Confused by this, I repeated the process a few times, and eventually the clutch pedal did not return to its original position at all any more :mad: I also noticed that hardly any fluid came out of the bleeder valves any more.

 

It almost seemed as if the master cylinder wasn't sucking in any new fluid from the reservoir :roll: Can that be?

 

Shot master cylinder? Couldn't see any signs of leakage when I started this whole adventure (wish now I hadn't :lol: ). Both cylinders seem to be able to pump out fluid, the master one just not feed itself with fresh liquid :roll:

 

That's the Midlands Meet slightly screwed then, as I have no car :mad:

 

OK, as a last resort I could attempt to bleed the clutch cylinders using the front left brake cylinder, but I haven't got a hose that's long enough to reach :mad:

 

Any suggestions, ideas? All welcome :-)

 

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[stevemac 0]

Although I'm not completely familiar with the internal design of the Corrado master/slave setup, it is possible for some cylinders to leak internally - with no external fluid loss.

 

On Mercedes 190's, the seals inside the cylinders used to turn inside-out - used to be quite common.

 

Given the age of the car, my suggestion would be to replace the clutch master & slave cylinders.

[Supercharged 2]

Yeah - was gonna say that Steve, the Slave will leak into the clutch housing but not sure if the fluid in the master has anywhere to go - inside the car maybe??

 

Also agree that if the MC is original, it would be a good idea to change it and you'd do the slave too as the new ones have plastic internals and don't fail like the old metal ones - also check the flexi pipe that feeds the slave.

 

Anyway Eric, it could be worse - at least your clutch pedal hasn't failed!! :lol: - I assume Jim told you about that...

[stevemac 0]

not sure if the fluid in the master has anywhere to go - inside the car maybe??

It will leak past the piston inside the cylinder - one possible cause of the pedal not returning correctly.

[Tempest 0]

OK, thanks for the tips so far. I already thought of the cylinders having failed, but why during a bleed? Before everything was working fine, as far as I can tell, no clutch binding (suggesting good pressure on the push rod inside the gearbox) or slipping (suggesting no fluid leaking into the clutch housing).

 

I'll first check the blue-textile wrapped feed hose to the master cylinder to see whether that's clogged, as soon as the weather permits again :roll: Really could do with a 3rd garage :lol:

 

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[RW1 0]

Starting with the master cylinder, I opened up the valve, pressed the clutch pedal, and immediately noticed how the pedal stayed down

 

Not sure where you've got to with this old boy, but the clutch pedal assembly is sprung assisted. Push it with the slave cylinder open past about 1 inch of depression and the spring takes over. The pedal zips into the footwell fairly pronto!! Must always "hold" the pedal by hand when pushed with the clutch slave bleed nipple open. Then close the slave nipple and pull the pedal back up by hand. Repeat to bleed through and make sure the brake reservoir fluid level remains above the clutch hydraulic tap off point.

 

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[Geo 0]

You shouldn't even have to pump the clutch pedal to bleed the system.

 

If you just open the bleeder on the slave cylinder gravity will do the rest for you.

 

And it sounds from your description as though you pumped the pedal up and down with the bleeder open. This is a bad plan as air gets drawn back into the system, which is probably why your pedal is softer than it was before you started. The correct procedure is to pump the pedal a few times then hold it down while someone else opens the bleeder and then closes it again before you release the pedal.

[Tempest 0]

Yes I realised that now as well, as that is normally how I bleed the brakes, but alas the clutch seems to be different.

 

The other problem is that I don't have a 2nd person to help me (no girlfriend or wife, and having a friend come over is always a bit awkward, as I really don't plan these things :lol:).

 

In the end I got there with a bottle of toilet cleaner filled with fresh new brake fluid, squirted that into the slave cylinder bleed valve until it came out of the master cylinder bleed valve, then rebled the master cylinder and job done. Tested the gears wth engine switched on, and they all engaged nicely, and the car also didn't start to roll out of its own whilst in neutral.

 

Now why doesn't the Bentley mention anything about clutch bleeding, as it is so different to brake bleeding? :mad:

 

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[Jim 2]

If you ever need a spare pair of hands Eric, let me know.. i'd love to come over and help with car tinkering. Just text / call me whenever.. If i'm unavailable i'll say so, but if I can make it, i'm desperate to learn a bit more about car repairs etc!! :)

[RW1 0]

Now why doesn't the Bentley mention anything about clutch bleeding, as it is so different to brake bleeding?

 

Cos it's missing two pages! But a warning does appear on page 30.4.

 

I use a long tube into a bottle and hand pump the pedal. The tube in the engine bay is initially vertical with the nipple left open to ensure a head of fluid forms and the air rises. It's part of a large vacuum brake bleeder that collect 4.0 ltrs.

 

Glad you're sorted now :thumbleft:

 

 

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[Tempest 0]

Thanks :-)

 

But a warning does appear on page 30.4.

 

Yeah, the one about not pressing the clutch pedal with the slave cylinder removed.

 

Cos it's missing two pages!

Not anymore from tomorrow. Indeed my Bentley now almost consists of more added in leaflets than the actual book itself :lol:, as particularly on the G-Lader side of things it's, just like VW's information (who originally declared this thing as non-servicable :lol:), quite poor.

 

Thanks for the offer Jim, but you know me, I'm a bit reluctant of having to shout for help in an emergency :lol:

 

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[Jim 2]

Well as I say.. I want to learn and have been meaning to say that i'd like to watch / help out whenevr you have to work on your car. If you need a hand, please ask. If i'm free i'd like to be able to help out! :)

[Tempest 0]

Well after all that fun bleeding my clutch cylinders, I took the Rado for a good spin tonight. The squealing is still there (see relevant thread in Engine Bay), the squealing is also still there when idling with clutch depressed, and revving the engine, still can't really pinpoint it, though, but, I couldn't help but notice that engaging gears was a wee bit smoother when letting the clutch go, and I had no difficulties at all getting into 1st gear when, for example, waiting at a traffic light.

 

Hope this stays like that, because then it was all very much worth it :-)

 

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[RW1 0]

The squeeling symptom sounds like the clutch release bearing is noisey.

 

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[Tempest 0]

The squeeling symptom sounds like the clutch release bearing is noisey

 

Hmm, bear in mind though, that I get this squealing sound with the engine idling, irrespectively of clutch position (i.e. both depressed and released). It only occurs when moving the throttle as well (accelerating, not decelerating), not when holding it steady. I had another listen yesterday, but still couldn't place it :-(

 

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[Jim 2]

Has bleeding the clutch cured the problems with awkward shifting into 1st gear Eric?

[Tempest 0]

I took the Rado for a good spin tonight ... and I had no difficulties at all getting into 1st gear when, for example, waiting at a traffic light.

 

Jim: As posted by moi earlier ;-) Hope it'll stay, not that I was just on a lucky night last night :lol:

 

Right, that still leaves 2 probs to sort, the stuttering at start (my ebay seller still hasn't sent me the fuel pressure testing gauge, even after 3 weeks!!), and the squeal. Oh well, getting there, by which time, numerous other problems will have introduced themselves :roll:

 

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