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Clutch Master Cylinder Issue

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Rob Glasgow

Rob Glasgow

Jedi Knight
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My Clutch MC started leaking last month. I decided to replace both the Brake and Clutch MC since they are a pain to get to and at my age I think this should be the last time I will need to mess with them. Prior to the leak, the clutch system was working perfectly. I replaced the clutch 1000 miles ago and the slave cylinder doesn't leak. New SS slave hose.
After installing both MCs, I bled both systems. The brakes came up fine with a firm pedal. The clutch is hit or miss. 8 to 10 pushes with a firm pedal, then the next push goes all the way to the floor with no resistance. Not a squishy pedal like it had air, but no resistance at all. I re-bled the slave both using traditional two person method and a vacuum pump until no bubbles. No improvement. I called the supplier to see if they had reports of faulty units. He said they hadn't but offered to send me either a new MC or a repair kit. I told him I would check with my advisors on the forum to see if they had any suggestions.
So, two questions. Do you think I got a bad MC or still have air in the system? If I decide to try a repair kit rather than a complete MC, can I install it from the inside the cockpit or do I have to remove the entire MC first?
 
Symptoms do not sound like air still in the circuits, at least not to me. But before the hassle of taking it apart again, you might try "bench bleeding" the master cylinder.

You can do that in situ, if you have a scrap length of pipe__or even buy a length locally that you can cut/bend to suit. From the output port of the m/c, run the pipe into the reservoir at least an inch or more below the fluid level of the appropriate chamber.

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Ideally, you'd have someone else to stroke the pedal slowly to the floor several times while you're watching for bubbles. If there's any air in the cylinder, that should get it all out. Note that you'll have to purge the pipe of air with the first few strokes.

It is possible to install the rubber kits without removing the m/c, but I don't recommend it. To save time on jobs, I used to hone them and assemble the kits into the cylinders while they were still mounted, but I myself was still rather rubbery nearly forty (<40) years ago!
 
It doesn't sound like air in the system to me, either. If it was air, it would be uniformly squishy. It seems like the MC is not sealing off the reservoir when you apply pressure and the fluid flow is going into the reservoir instead of down the pipe to the slave cylinder. It would be easiest on you to have them send a new MC.
 
Get a new MC. I wouldn't waste my time putting a kit in a brand new cyl. many years ago I had all my hydralic cylinders brass sleeved. the brakes went together fine and bled up quickly. But the clutch gave me fits. I sent the clutch MC back and they said they rebuilt it again and I still could not bleed the clutch system. I sent it back 3 times. almost 3 months were lost trying to get a good clutch hydralics. Finally I just went to another supplier and bought an over the counter new cylinder (no brass sleeving) and it went in and bled up the day I got it. It is still in the car and works good. Don't know what was wrong with that other sleeved cylinder but it never did work. the refitter never got it to work either.
 
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