Clutch Master Cylinders breaking?

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clipper47
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Location: Ontario, Canada

Clutch Master Cylinders breaking?

Post by clipper47 »

On a recent road trip the clutch pedal went to the floor during an upshift and then stayed there! I managed to get the car home and found that the clutch master cylinder was broken. The rod was flopping around loose. I ordered a new one and installed it. I bled the system and the clutch pedal was back to normal for exactly two pushes and then the pedal went to the floor again. I rebled the system again using a pressure bleedr and then changed the slave with another good one. Both slaves seem to be fine but the master cylinder appears like it may be broken again as there is very little resistance in the rod. The pedal box does not appear to be cracked and it has the reinforcement kit installed also. I am thinking that if the clutch disc/ throw out bearing fork is jammed and the slave rod is unable to move it would that cause the hydraulic pressure on the master cylinder to be great enough to ruin it when the clutch pedal is pushed. Is there a way to see if the clutch fork/ brake disc is stuck without removing the transmission. Should I be able to move the clutch fork manually using a screwdriver etc. or will resistance be too stiff? I am at a loss as to what to do at this point so any help appreciated.
Dave
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1985 635CSi US
Cosmos Blue/Pearl Beige
wattsmonkey
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Re: Clutch Master Cylinders breaking?

Post by wattsmonkey »

On my very first foray into E28s/E24s I had a 528i with clutch problems. I found two pieces of metal in the bellhousing which turned out to be the "ears" from the release bearing. I don't know how far into the past this had happened, but the slave was also knackered, which might be because of it going beyond its normal travel because of the broken ears and the additional fact of the friction plate being worn out.

The helper spring can also do counter-productive "not helping" if set up incorrectly.

I'm sure you already know how much of a pig the clutch can be to bleed, too.

Hope you get it sorted soon,

ROb
"Most of it necessary; all of it enjoyable." LJKS
'84 635CSi, dogleg...itbs and supercharger????? Eaton Mess
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clipper47
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Joined: Mon Oct 10, 2011 12:22 am
Location: Ontario, Canada

Re: Clutch Master Cylinders breaking?

Post by clipper47 »

Rob, Thanks for your quick reply and insight. The clutch worked fine up to the time the pedal went to the floor the first time. I installed a used but good master but I am hesitant to hook it up and test it after destroying a second new one after only two depressions of the pedal. My instinct tells me that the pedal box is likely cracked. The master can't move because of the reinforcement plate so I will look more closely at other areas of the box. I rarely use the car anyway so it will not be a rush job.
Dave
_____________
1985 635CSi US
Cosmos Blue/Pearl Beige
User avatar
clipper47
Posts: 596
Joined: Mon Oct 10, 2011 12:22 am
Location: Ontario, Canada

Re: Clutch Master Cylinders breaking?

Post by clipper47 »

I removed the pedal box yesterday expecting to find a crack somewhere. It is in perfect condition with no signs of stress crack. Not sure what to do now except to install it all back together with my spare master cylinder and see what happens. The new master was a Febri and the previous one that broke was a Sachs (about 3 years old ). Possibly it is a case of defective parts?
I am going to see if it is possible for me to move the clutch fork through the slave cylinder hole.
Dave
_____________
1985 635CSi US
Cosmos Blue/Pearl Beige
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