Clutch adjustment gone weird - now ok

[vincereynard]

Checked and reassembled master cylinder and it appeared to fix the problem. Clutch pedal then worked as normal and you had full travel for usual operation. Drove about 10 miles to test and it gradually changed back to how it was before. Full pedal travel won't work and half travel lets you change gear ok. So it's not a pedal travel issue. It seems to be to do with the hydraulics.

Does the fault disappear overnight?

Cleaning out the Master temporarily fixed it. To me that would suggest you still have a problem with the Master. It is not fully returning so that the issue builds up over a short run.

Sitting in the car, can you replicate the fault by repeated pedal depression? Does the clutch arm in the bellhousing return to the same position every time and still have clearance?

I have a spare slave that you could try but I doubt it's the problem.

[Melodyk]

Thanks for the replies. We are going to check out a few of these things this morning. When we got the car we also got a proper car ramp so we can walk under the car which does help moral in these situations! It doesn't help with getting at the master cylinder though unfortunately.

[rgh0]

All the external bits all appear to be working properly from your description. The issue is probably unfortunately some internal failure, There are a range of potential causes but its probably an engine out job to further diagnose.

cheers
Rohan

[Craven]

There was a guy on here not so long ago where the clutch fork fulcrum pin/pivot had come loose in the bellhousing giving strange slave pushrod adjustment, worth a check.
Ron.

[2cams70]

When the engine and box were out how long were the clutch hydraulic lines left open? Did you seal them?
The residual brake fluid is hydroscopic and will absorb moisture over time which can lead to internal corrosion of the master and slave cylinders. In the master cylinder did you check thoroughly the little round seal at the end that blocks off the orifice to the brake fluid reservoir? Did you inspect inside the cylinder for pitting around this orifice where this seal seats?There's also a little wave washer on the stem behind this seal which often goes AWOL

[Melodyk]

If we push the slave cylinder piston right back by hand initially then the clutch pedal goes full travel and disengages the clutch so you can change gear normally.
The slave cylinder seems to retract a bit slowly towards the end of its return phase. When you declutch the next time it pushes the clutch too far. Half pedal length would be enough to disengage the clutch and fully depressing it goes over-centre and actually engages drive again. Hence not being able to change gear by pressing pedal to floor.
We are going to have a look at the master cylinder again to see if it's not letting all the fluid return fully.
It has been a long weekend.

[Panda]

I'm not a betting man, but I would put money on it having at least a faulty master cylinder. The variable height of the "bite" position points to this. There may be a pit or area of wear in the cylinder bore which is allowing the fluid to bypass the seal internally and cause the piston to retract making gear selection difficult. Should be possible to observe with car jacked up safely and someone operating pedal.
Alan P.

[2cams70]

Be sure to check the slave cylinder too. Sometimes a build up of corrosion will occur under the boot between the piston and cylinder wall causing sticking. Suggest you dismantle, clean and reseal or fit a new one. Your further explanation points to the slave cylinder more so than the master cylinder now.
If the main piston seal is weeping slightly corrosion will build up here whilst the cylinder is inactive which it has been for around a year.
If the slave cylinder sticks rather than returns each time the master cylinder is actuated "pump up" of the slave cylinder will occur.

[Melodyk]

You are all so helpful. It's nice not to be struggling on alone! I have ordered a new master cylinder, slave cylinder, spring, snap ring and braided hose. My husband has ordered some proper circlip pliers to do the snap ring as he is sick of fighting with it.

[vincereynard]

You are all so helpful. It's nice not to be struggling on alone! I have ordered a new master cylinder, slave cylinder, spring, snap ring and braided hose. My husband has ordered some proper circlip pliers to do the snap ring as he is sick of fighting with it.

"Drove about 10 miles to test and it gradually changed back to how it was before."
That's the telling part.

All the new bits should do the trick. If the braided hose goes from the Master (i.e. is in one piece.) you can bleed the system by holding it above the new master before finally putting it in place. (Slip it in place, attached and tighten hose in the final position, take it out and bleed it, (ensuring the slave piston does not shoot out), stick it back in final position.)

Good Luck
Vince

[Melodyk]

Yes there's not many more new bits we can throw at it really. We had the engine out last weekend to have a look inside the clutch and all was still quite new looking. If something there was broken or failed it would not work intermittently would it. It's interesting about the slave cylinder over-pushing and making the clutch plate go beyond where it needs to be. When you push the pedal to the floor and cannot get any gears you think the clutch has gone. But if you half press the pedal you can get in gear ok. Bit disconcerting but ok to get you home from a test run. On the plus side it did pass its MOT last week just before all this happened.

[bob_rich]

Hi

reading all the other posts I think you may have a variation of a problem I had on the hydraulics on my Lotus 7 clutch. when I rebuilt the car everything in the clutch hydraulics was new except I used a used flexible brake hose that seemed OK when I examined it.

after driving for a few miles sometime as much as 50 + the clutch exhibited what looked like severe slipping after a gear change. Further more at traffic lights when I let the clutch up to move off it did not engage for sometimes as much as 5 seconds then slowly engaged even when my foot was off the clutch pedal! when the car fully cooled down and car started up again the problem disappeared but agin returned after a anything form a few miles to 50+

I eventually traced it to the corrosion in the flexible hose that clogged up the to and fro of fluid flow and was giving a slow return. It may be that you have a variation on this problem in that the corrosion or dirt trapped in the flexible hose sometimes gives compete blockage which may or mayn't clear as the clutch operates and alters the bite point

I changed to hose to a New Goodridge part bled the system through to get nice clean fluid and problem has cleared up completely.

Hope this helps and I hope you fix it OK

regards and best of luck

Bob

[661]

While you are there..... you could fit a remote bleeding hose to the clutch slave cylinder just to make the task easier.

[Melodyk]

Fitted a new master and slave cylinder but used original braided hose between the two. It is now working ok. We think it was probably the slave cylinder sticking/not fully returning so next time you pressed the pedal it pushed the piston too far forward. There didn't seem to be anything wrong with master cylinder but it's possible there was a fault there. By the time I got home from work my husband had changed them both so no chance to eliminate one of them. The key point was that it was the hydraulics at fault not the clutch mechanism. It's well worth trying to half press the pedal to see if you can engage gears as a fully pressed pedal gave the impression of a faulty clutch but it had just over-travelled and gone beyond fully disengaged to starting to engage again. The diaphragm sort of turns back on itself. I hope you like my layman's way of explaining it. I am not a mechanic!