Clutch wouldn't disengage, now it does

taylorcom

taylorcom

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Hi all,

I have a '70 2800CS that I was driving home in hot weather yesterday (Berkeley, CA). When I got 2 blocks from home, the clutch started to feel weak, and would barely disengage.

I let the car sit overnight and just now tried it again. At first, the clutch wouldn't disengage fully when I tried starting the car in gear with clutch pedal depressed. Then I pumped the clutch pedal a bunch of times and it started working fine again.

At first glance, you'd probably say there is air in the hydraulic system. But I haven't touched the hydraulic system, and hydraulic fluid level has not changed at all ... it's where it should be.

What am I missing here?

Many thanks in advance ...

Steve
 
Master cylinder or clutch master???

Carefully check below your clutch pedal for any sign of hydraulic fluid leakage--feel the carpet there to see if any signs of leaks--if wet your clutch master is failing.

If it turns out to be a failing clutch master I have one available that was rebuilt by Bimmer Doc aka Carl Nelons shop--never used--see my list of parts FS on the parts FS siie.
 
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@ Blumax & Dave G,

No leakage is evident from the clutch master. Plus, there has been no reduction in fluid in the reservoir.

Could the clutch master cyl. be failing, but not leaking?

BTW, for many years I owned a '71 Triumph TR6, which is prone to hydraulic system failure. I got pretty good at rebuilding its brake master cylinder ... haha

Thanks,

ST
 
Also a possibility: it was a hot day (about 80), the hydraulic fluid hasn't been changed in many years. Maybe the fluid has taken on moisture, which might have turned to steam in the heat, causing a temporary malfunction. However, the brakes seemed to work just fine & they're part of the same system.

I just drive the car again (into my garage) and it seemed to shift ok. But I don't want to be on the road 20 mi. from home and have the clutch suddenly stop working again ...

Any & all ideas are welcome ...
 
NO WAY that moisture is boiling in the clutch when it's only 80 degrees F.

You stated the "clutch felt weak" but what, besides that the clutch wouldn't disengage, does this mean?

Is this car driven regularly? If not, possibly the clutch disc has stuck to the flywheel and/or pressure plate faces, just as drum brake shoes can stick to a brake drum. Alternatively, maybe the disc isn't sliding on the trans input shaft splines. Both of these are most easily remedied by more driving, since you probably don't want to take out the trans.
 
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hi

i went through a complete rework process on the clutch cylinders

the sympthom was a very soft clutch pedal, but that did not meant problems in shifting the gears anyway

while that soft pedal was on i realised that the brake fluid reservoir level was not stable, and it went down with each drive, not dramatically, but some like 5mm in a week

together with that the brake fluid was becoming brown instead of green-yellow pretty quick

finally i realised that brake fluid was coming out in the pedal area, and the carpet was a little wet in the top area near the brake plate

i dismantled all the system, and replaced the joints and gaskets, those were badly worn, so fluid was leaking away from the master cyl

once fixed, the brake fluid level is stable, the colour is green-yellow and the pedal is a little more hard to press

considering what you have said, in which no leakages are observed i would consider what is happening inside the bellhousing, i mean, the slave cyl is pushing a plate that (depending on early or newer type) will act on some other mechanical elements

i would check them to be sure that no strange things are happening

if you like to take a look to my write up with pics you can search in the forum under clutch cylinders, projecta and restorations, my car is manual dated 71
 
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@ Honolulu, Yes, the car is driven several times per week. 'Weak' clutch pedal meant it seemed a little easier to depress than normal. Now it feels normal again.

@ deQuincey, The fluid level has been the same for a few years now, so I don't think leakage is likely.
 
@ deQuincey, I just checked out your pics and they are terrific ... it's a great guide into the inner workings of clutch hydraulics.

Question: When you rebuilt the cylinders, did you do need to do any prep to the insides of the cylinders (bore them out first)?

Thanks again for the great documentation!
 
Sometimes you can just disassemble, clean up the bores, and replace the seals.
But...Usually these things fail because the bore gets corroded from water in the fluid.
Sometimes you can clean them up with a brush hone.
If the bore doesn't clean up, then it's usually better to just replace the part with a new one.
Boring and sleeving only makes sense if the parts are un-obtanium
I think the CS master is NA but the '02 part is a possible replacement with a minor tubing change.
DaveG
 
@ DaveG, Sounds good.

@ All, Another possible cause just came to mind: the rubber tube (Clutch Flexible Pipe). I know the brake rubber tubes need to be replaced periodically.

Could an old clutch tube be causing the problem (weak clutch that won't fully disengage in warm weather, which improves if you pump the clutch pedal a lot)?

Thanks...
 
taylorcom said:
@ deQuincey, I just checked out your pics and they are terrific ... it's a great guide into the inner workings of clutch hydraulics.

Question: When you rebuilt the cylinders, did you do need to do any prep to the insides of the cylinders (bore them out first)?

Thanks again for the great documentation!
Click to expand...

no need any special prep, except clean inside with a cloth embeded in gasoline, clean until all possible rubber debris or dirt dissapears

you are welcomed

happy to know that it can be useful
 
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