Clutch not engaging

[grasshopper]

Hello all, here is the problem: 1974 Ser III with original tranny/clutch with 55K miles. What I thought was a clutch failure of the 37 year old system last fall had symptoms of driving fine for about 5 miles of city stop and go, then slight failure pulling away from a stop sign to almost a complete failure attempting to get up its slight driveway. It resulted in the removal of the tranny, replacement of the clutch, pressure plate and bearing. No oil present in the bell housing at rebuild. All the rest of the seals and gaskets were replaced. All bearings and gears were fine. Prior to the clutch replacement, about 1.5 years ago the master was rebuilt and the slave replaced all together with new copper lines and LR DOT 4 fluids.

So, now the same symptoms have reappeared. Goes in town for a few miles, then slow failure of the clutch to total failure. Let it sit for a while (like have lunch) then it works again for a while. I believe it to be a hydraulic problem, but what I would like to know is if anyone has experienced this before prior to me having to replace something. Thanks in advance.

[SafeAirOne]

Is something causing the hydraulic fluid to boil (exhaust system or whatever)?

[grasshopper]

The lines are routed exactly like the originals, so I don't think it's boiling, although I guess anything is a possibility. The engine does not overheat. And it worked fine for over a year.

[I Leak Oil]

So it works fine when cold, slips when hot? Perhaps the adjustment is off causing it to slip. Grabs when cold but after slipping enough it heats up and then no mojo....Just a guess.

[cedryck]

start with the basics

Start with the basics, check the adjustment in the green bible with the calipers as shown, try preasure bleeding, perhaps there is a bubble in there,,,,,,

[grasshopper]

I'll try an adjustment check this weekend and let you know. Thanks

[grasshopper]

I bled the lines when I replaced the clutch 6 months ago. Had to take the line off to get the slave off the housing. Ran fine for few months. Life was sweet.

Okay, so I remembered, confirmed in the green bible and saw first hand the Series III clutch is self adjusting. So, I really think the system failure is in the hydraulics. I will for a moment assume the slave is okay since it was new, and the lines are okay since they were also new. The only old part (rebuilt) was the master. I feel stronger now that the problem is in there. Perhaps my rebuild 1.5 years ago should have been a replacement.

Though, the slave could be a flub, or crudded up with debris from something. Or, it could have air in the lines, but wouldn't that just cause a squishy pedal? I think, but could be seriously wrong, the master is not letting the pressure release back to it due to something amiss, and after a few pedal strokes in short city driving, there is a buildup and non-release holding the clutch out. Then a slow release until starting up again. If an air bubble can do that, I will bleed again. If not, then I will have to replace something, probably the master at this point, then a flush and bleed of the line.

Thoughts again?

[jac04]

If the push rod adjustment at the master cylinder isn't correct it will cause the symptoms you describe. First check is to remove the return springs from the pedal and check for a little free play. Then remove the inspection plate from the clutch tower to get in and verify/adjust the push rod adjustment.

[bpj911]

rubber line

change the rubber line.

[bpj911]

I meant to say check

check the rubber line and make sure it's letting the pressure back. Also check for the little bit of freeplay you need at the master or it will build and won't let fully engage.

[grasshopper]

Thanks for the advice on the master push rod. I will check this weekend.

The rubber line was replaced a short time ago when I replaced the lines with copper. But I will double check to make sure it is not pinched or kinked.

Derek