Sinking clutch pedal

[oxford jack]

This query relates to a '73 +2. I have read through many of the posts on clutch pedal woes and not found a definitive answer.
When used normally the clutch works fine and gear changes are noiseless. If I rest my foot on the pedal it sinks to the floor without operating the clutch. Is this air in the system or fluid bypassing the master cylinder piston do you think, or perhaps another problem?

I have limited time, need the car for a trip to Scotland in about two weeks and I am wondering if I should just go to someone who knows how to fix it. Your suggestions for a garage or mechanic who is competent and within striking distance of Oxford would be very welcome.

Thanks in anticipation

Jack

[Chancer]

Fluid creeping back past the piston seal into the reservoir, using the clutch fairly quickly minimises any leakage, the seals can sometimes be persuaded to expand by blocking off the outlet or the clutch are and standing on the pedal (much easier with brakes) years ago there was a technical term for this called scragging a seal but it became associated with other less pleasant past-times

I used to have to do this a lot with my vintage Bradbury trolley jack but the seals are now past redemption.

Worth a try perhaps and not likely to cause a catastrophic failure.

Famous last words................

[collins_dan]

My guess would be master cylinder needs a rebuild. I once had a leaking master cylinder and when I reassembled, I put the seal at the end of piston in backwards by accident and the pedal would sink as described. Simple master cylinder rebuild kit should do it. Others should comment as mine was a dual circuit S4 with no servo, so a bit of a different set up. Good luck. Dan

[mbell]

I'd suspect the "valve seal" in your master. When the pedal is pressed it should seal the hole to the reservoir from the cylinder allowing the pressure to build in the cylinder and be transmitted down the line via the fluid. It seems under light pressure to not be sealing and allowing the fluid to escape back to the reservoir. Should be able to check by monitoring the fluid level in the reservoir as someone else presses the pedal slowly.

The fix is a rebuild of the master cylinder with new seals (or fit a new master). The seals are pretty cheap and the rebuild is straight forward if the master is in reasonable condition. You'll need to remove the master from the car, disconnecting the push rod from the pedal is tricky as it has to be done from the drivers foot well reaching up (unless someone has modded the pedal box to give top access). Bleeding the clutch can be a real pain too.

I'd try get it fixed before the trip if possible. It is all just standard Girling parts so any decent garage should be able to handle it with out issue if you don't want to.

[Sea Ranch]

. . . by blocking off the outlet or the clutch are and standing on the pedal . . . Worth a try perhaps and not likely to cause a catastrophic failure . . . Famous last words................

Sorry, Chancer. Don't know what you're sayin' . . .

Really, at this stage, who cares why you have a sinking pedal. It's obviously hydraulics at fault, so just get that master rebuilt or replaced. It's at the top of the fluid chain. If that cures it, you're ready to go. If not, then rebuild/replace the slave. Done.

Whatever you do, don't gamble your trip on the situation not getting worse. It probably will (get worse) and at the worst moment (night, rain, out in the boonies . . .)

Good luck, and have a great trip!!

Randy

[john.p.clegg]

and try to use girling seals,NOT seals for girling made in Taiwan...

John

[oxford jack]

Thank you all for the convincing and unanimous verdict. Girling (noted) seals ordered this am, I will attempt the gravity defying dive below the pedals and rebuild the blighter, see how it likes that then!!

I appreciate your assistance thanks a lot

Regards Jack

[gjz30075]

Just do both (master and slave) now. Shotgun the problem at this point, if you plan on using the
car soon.

[Sea Ranch]

You're probably right, Greg.

But let's let him tackle the master first. See how he does. Then, if he's feeling confident and still has energy and enough attitude left, we can have him do the slave, too.

Get along, now, Jack; we're waiting . . .

[billwill]

If the problem was in the slave he would be losing clutch fluid as it would not get back to the reservoir.

[gjz30075]

Absolutely right Bill. I'm just suggesting it as a preventive measure.

[collins_dan]

The weak point in the system now is the master. Once that is improved, the weak point will shift to the slave. In my experience, fix one and the other goes very soon there after. I'm with Greg. Get the slave rebuild kit, it will likely be needed shortly. Dan

[denicholls2]

Others should comment as mine was a dual circuit S4 with no servo, so a bit of a different set up.

Now there's a man who really wants his clutch to work.

[oxford jack]

You were all correct it was the master cylinder seals, replaced and all was well.

When I say well, it may be some time before I am well again, what a job! It was obvious as soon as I removed the drivers seat, crawled upside-down into the foot well that the clutch linkage would not be coming out that way. So the pedal box had to come off and that means the brake cylinder had to be drained, so it would be wise to rebuild that at the same time was my thought. A 3 hour round trip to collect the parts and begin.

After disconnecting everything and prizing the pedal box loose from the sticky black seals to the body, I could find no angle at which the pedals would come through the opening in the bodywork? So I removed the main pivot pin and some struggle got it out. Rebuilt both master cylinders, no problems, but it is interesting how much more one gets from one spares source and how much less from another for similar job!

Assemble the pedal box components, and then spend an hour fiddling the pedals back through the opening, bolt it all back and put the interior back together. The clutch bleeding took five minutes (I had rebuilt the slave about two years ago) no issues and seemed ok. The brakes took three of us about two hours to bleed and the peddle is still not quite as good as before. One peddling, one topping up the cylinder and one at the wheel bleeding.

The whole job took me about 12 hours and a lot of toil, what a crappy arrangement for renewing and working on the cylinders, not the proudest Lotus design element I would suggest.

The trip to Scotland however took place. Left on Thursday last, 540 miles to Strathdon in Aberdeenshire. A late evening blast up and over Glenshee pass in the Cairngorms, no other traffic and just the deer to watch out for. The silencer bracket fractured about 15 miles before the destination but soon cobbled with a jump lead and repaired locally for a few pounds.

The return was ok, puncture on the M6 which was less than amusing getting from the outside lane onto the hard shoulder, traffic from Manchester to Brum was awful, but home in 11 hours including stops. 36mpg and both driver and passenger comfortable if not a little tired. 1,100 miles in total.

Thanks so much for your sound advice and wise council, good job I was not warned how b.difficult it would be to do the repair, I would have not started, glad I did, wonderful trip.

[Sea Ranch]

Excellent story, Jack! Both the repairs and the trip. Very nice.

This is the kind of thing we like to hear/read: someone else doing all the work, while we give the advice

I do know what you mean about the work, though; I recently did piston rings, cylinder hone, con rod bearings, a couple new exhaust valves (seated by the local shop) and also re-ground the valve "lifters" (inverted buckets) to set valve lash all around, on my 98 Corolla. This is the kind of thing you don't want to do, but once you set your mind to it and determine to get it done, it happens, and you're proud of the result (or if not, at least glad it's done!).

So, one more job on the ol' Lotus you're now well-versed in; next time it will be you giving the advice and waiting around for someone to report their results

And I envy you the trip in the Lotus; will be another couple years before I can do that Hopefully many more drives like that for you this summer

Regards,

Randy