Clutch Not Disengage

[bengalcharlie]

Hi guys,

I have been strugling with the clutch for a while now.
both master and slave cylinders have been fitted with new seals and they are not leaking.
problem is that the slave cylinder pushrod does not travel out enough to free the clutch plate from the flywheel.
master cylinder is girling and 5/8
slave cylinder is girling too and 7/8.
are these the correct sizes?
I do need a rod travel of the slave cylinder of 17mm.
at present I only get about 9mm
the rod travel of the master cylinder is about 17mm ( I did some calculations and that is what I came up with)

As a solution I see the following;
change the master cylinder to a larger diameter and the same as the slave cylinder, ie 7/8
the pedal pressure will increase but I will get a working clutch??
I do hope some of you out there can advice me.
I hope to get the car on the road soon now after 15 years!!

robin in NZ

[Foxie]

Robin,

There should be absolutely no reason to change master or slave cylinder sizes.

It may be obvious, but have you adjusted the operating lever at the clutch ?

Is the clutch / clutch release bearing badly worn ?

Is the release arm etc. properly assembled ?

17mm travel on the pedal represents 3.365 cc, 9 mm on the slave represents 3.492 cc, so there's not much wrong here.

I'd like to measure the actual movement on my cars but I have a BMW over the pit at the moment, however I'd say 9mm is plenty of travel.

Sean Murray

[type26owner]

The clevis on both the brake and clutch pedalbox linkages are prone to wear out. Typically about half the useful travel of the pedals is eliminated when this happens. It happens very slowly also you never notice it going away until the pedal no longer functions correctly. You'll need to lubricate the linkages at least on a yearly basis to slow down the wear rate next time. Dive under the steering wheel and look at the bellcrank linkage of the clutch. Where it couples onto the shaft which moves the master cylinder piston is the clevis. It's worn out if you can depress the pedal by half it's travel and the piston does not move. Happens to every car eventually.

Don't use any DOT5 silicone brake fluid in the clutch. The seal material of the slave cylinder is not the same as is required of brake components and is attacked by the fluid. It will swell to twice it's size and turn all gooey. Just removed a seal which had been damaged in this way from my slave cylinder two weeks ago. Can take a picture of it and post here in a few days. Brake seals are normally EPDM and are unaffected by all the brake fluids as required by USA Federal Transportation laws. Don't have a clue what the slave cylinder seal is made of but can state it came from DBE a few years ago. It was not leaking. I just did routine maintance to prep for the upcoming trackdays and discovered this ready to fail situation. Guaranteed to fail while on the racetrack ruining a trackday. I was lucky.

[Evan Carpenter-Crawford]

Has the car been sitting for a while? If it has then the clutch disc could be frozen (i.e. - rusted onto) the flywheel. This hasn't yet happened to me, but from what I've read it is a common problem with cars that sit for extended periods. Do a search in the email archives and you should come up with at least a couple threads on this. I seem to recall that for most the solution was to heat cycle the flywheel until it pops itself free. This was done by running the engine while in neutral until fully warmed then shutting down and letting it cool completely - repeat until the disc frees itself.
good luck.
-E

[bengalcharlie]

thanks for your replies,

However, all your concerns have been checked and I could not find anything.
I do confess having filled the system with silicone fluid and although the seals are fine, no leaking or swelling( I did fill the sytem more than a year ago) may be there is more compression of the fluid and therefore less travel??
I have been using silicone fluid for about 20 years now in different cars without any problems.
the clutch plate is not rusted to the flywheel. but thanks for all your good advice.
cheers

robin

PS I will recheck everything and also check the position of the clutch fork although I can not see anything wrong

[type26owner]

I love the silicone fluid too but only for my cars that never driven at 10/10s. This is the first instance I've found where it damaged a seal. Don't think it would account for that kind of loss of travel from the slave cylinder though. Got me stumped. One possible problem is the flexible hydraulic hose from the master cylinder points up and then bends over by 180 degrees before leading down to the slave. A massive air bubble can get trapped there. Too little flow rate while doing the bleeding could result in it not being flushed away.

[type26owner]

Now that I think about it a little more a swollen up seal could account for the loss of piston travel. Each time the slave cylinder is actuated it's suppose to return the piston to the fully retracted end of travel if everything else which moves with it is in perfect condition. The swollen seal could be stopping it from returning all the way back. I was horrified at just how badly the seal was deformed.

[lotus026]

I've sure never heard of DOT 5 / Silicone fluid damaging a seal before, thought that was the whole point of using Silicone - it doesn't damage seals! Sure never did in the few years I was using it in the hydraulics on my Mini, which definitely had the earlier rubber seals; then when I figured out about the poorer feel of Silicone when used in aggressive driving I switched back to Castrol fluid - though can now only find it at one place in my town.

On the clutch problem, I'd lean towards either the clutch disc being stuck to the flywheel or an air bubble in the line also. Think all the hydraulics are pretty much the same sizes between the Elan & the +2 so wouldn't think that would make any difference; and on my Elan the clutch disengages in the first 1/4 - 1/3 of the pedal stroke; I just wish that it took a bit longer stroke and was more gradual like most of my other cars. But then it wouldn't be a Lotus, with all it's quirks!!

All of the sticking disc problems I've heard of ended up being solved by being driven, getting the car warmed up first then aimed in the proper direction to be able to load it up once under way, then doing some speeding up / down with the clutch pushed in the whole time - sometimes the driver had to be pretty aggressive, but would break loose eventually. I'm sure you can figure out some mechanical way to push the release lever enough to determine if it's really releasing at all or if it's the disc that's stuck.
Good luck!
Dave

[type26owner]

Silicone brake fliud is a solvent of itself. Suspect the swollen seal is a silicone seal.

I just wish that it took a bit longer stroke and was more gradual like most of my other cars.

You can do that easily. It's just a matter of installing a smaller diameter Girling master cylinder. Longer travel and easier to depress. I did this on my dad's Lotus41 so he could actuate the Tilton twin plate racing clutch so he could continue to vintage race into his mid-eighties. Brought it down from about 100 pounds to around 30.

[bengalcharlie]

Thanks agian for all your replies!
It has been very helpfull, although this morning I woke up and decided to have another look at the car, you know sometimes when problems occur it is best to stop and think about things for a while.
Nevermind, I looked under the dash into the pedal box and saw a little bolt behind the clutch pedal.
I inmediately realised that this was a stop to shorter the lenght of the clutch pedal and I adjusted the bolt so that now I do have more pedal travel.(only about 3-4mm)
This in combination with the smal play I did have in the rod between master cylinder and clutch pedal due to an oval hole should hopefully be enough to solve the problem.
Idealy I would like to make this rod adjustable but will first try it the normal way.
If this does not work then I will install an bigger master cylinder and or install a longer rod.
I will keep you all informed
cheers robin

[type26owner]

Robin,
What you have done is unadjust the retracted height of the clutch pedal relative to the brake by twiddling with that stop bolt. Put that back where it was. The 'oval' hole is the worn out clevis. The extra play added to actuate the master cylinder is still there and will reduce the travel of the slave cylinder by the amount you have described. You have done nothing which will fix the problem. Replace the worn out clevis. Probably the one on the brakes is toast too so don't just ignore it. Eventually the clevis on the brakes wears until the linkage lever pinned into the clevis contacts the bottom of the U-shaped portion of the clevis then it slowly wears sideways until it breaks through. When that happens you will have no more brakes.

Everyone should be doing a yearly inspection of pedal assembly just prior to you doing the lubrication. Both clevis wear quite quickly if left without lubrication.

[type26owner]

Robin,
Let me use a picture to make sure we are both on the same page. The first two pictures show a clevis and the push rod that actuates the master cylinder. Is this the piece with the oval hole?
<a href='http://www.triumphcars.com/tct100307uf/week33.htm' target='_blank'>http://www.triumphcars.com/tct100307uf/week33.htm</a>

[bengalcharlie]

Hi Keith,

yes the clevis pin did have an oval hoel wich I have rectified in the meantime by welding and filing the hole back into shape.
I did replace the master cylinder as well there I was not 100% convinced about the condition of this unit.
I installed everything again and although I have not driven the car yet the first inpression is that the pedal is alot firmer but the travel of the slave cylinder rod is still marginal and therefore I have my reservations if I have solved the problem.
I will keep you informed of my progress.
I will take the back plate of the gearbox as well and inspect inside.
I have to check if you can actually see something, let alone correct things without removeng the unit entirely.

other things to check: plate stuck to flywheel and slave cylinder.
master cylinder and braided hose are brand new so I can eliminate these from being faulty
I will do a search on how to free a clutch plate as well, just in case
In the meantime what would I do with all my spare time if I did not own such a lovely piece of #$%^^???

cheers

robin

[type26owner]

In the meantime what would I do with all my spare time if I did not own such a lovely piece of #$%^^???

We all share the pain. It's our common bond!

[bengalcharlie]

HI all,

after a long day of working on the car, I know that the clutch is free, I did pull the clutch fork back and started the engine and I could shift the gears without any problems.
I had a little leak in the sleave cylinder where the hose coming from the master cylinder comes in but I sealed it with some lock tight.
However it is still not working and I still get not enough rod travel in the slave cylinder.
At the moment I do not know what to do next but I hope for a brainwave!
robin