Clutch not disengaging correctly

[Nick Whitehead]

Help and advice please.

I have a Triumph Vitesse 2 litre Mk2. I’ve replaced the clutch master and slave (p/n GMC205 516788). And the clutch cover and release bearing (GCK282 CLUTCH KIT 3 PIECE GT6/VIT - OEM).

The clutch is working but it’s a real crunch to get it into gear and the clutch bite point is very low.

Question 1. Should the clutch release bearing disengage completely and stop when the clutch pedal is not depressed? (It doesn’t) And if so, what makes it return back towards the gearbox away from the clutch cover?

Question 2. The collar which the release bearing is drifted on to and has a flange to engage the clutch release fork appears a bit worn. There is a ‘semi-circle’ worn in the flange where the clutch release fork goes. So the fork is always in the same place and collar does not rotate at all. Is this normal?

Question 3. I’m pretty certain that the clutch hydraulics are bled correctly. No air. How can I tell the clutch fork has the correct amount of movement when the clutch pedal is depressed to disengage the clutch?

Thank you.

[Nigel Clark]

I found when changing the clutch on my GT6 a couple of years ago it wouldn't disengage completely. The pedal went rock hard before it reached the floor of the clutch disengaged.

This was caused by the slave cylinder's piston reaching the limit of its travel before the clutch had disengaged. I hadn't changed the hydraulics and the new release bearing was identical in dimensions to the old one, so there must have been a difference in either clutch cove or friction plate.

I solved the problem by spacing the slave cylinder rearward with a 3/8" UNF nut under each of the slave cylinder's mounting lugs. The clutch has worked perfectly ever since.

Can't explain what changed to cause this... Could the diaphragm spring in the new clutch cover differ in geometry from the original?? I seem to remember a similar problem when changing the clutch on a mini more than 40 years ago!

Nigel

[Nick Whitehead]

Thanks Nigel. Such an obvious and easy fix.   And no gearbox out!

Any view on question 1. Should the release bearing disengage from the clutch cover, or is it constantly rotating?

Nick

[DanMi]

There is a known issue with some of the release bearings supplied today being not the same thickness as originals

[johny]

21 minutes ago, Nick Whitehead said:

Thanks Nigel. Such an obvious and easy fix.   And no gearbox out!

Any view on question 1. Should the release bearing disengage from the clutch cover, or is it constantly rotating?

Nick

The slave cylinder has a spring inside which should keep its piston extended so keeping the release bearing lightly in contact with the cover plate. It has to be like this otherwise the clutch pedal would be floppy at the start of its travel.

Your release bearing carrier sounds normal with an indent in one of its flanges to stop rotation. This does mean that the fork pins always operate in the same place causing wear and if excessive people have found ways to modify the carrier for example by putting an additional indent in it so that the pins are then held in a different place...

[NonMember]

39 minutes ago, DanMi said:

There is a known issue with some of the release bearings supplied today being not the same thickness as originals

Yes, and that puts the release arm into the wrong geometry, so Nigel's washers under the slave may not work. The fix in this case is to put a washer or two under the mushroom pedestal that the arm rocks on. I was hoping this could be done in situ (because my GT6 has exactly the same problem with its new clutch) but it looks impractical and I'm going to have to get the 'box out again. Grrr...

[Nick Whitehead]

31 minutes ago, johny said:

The slave cylinder has a spring inside which should keep its piston extended so keeping the release bearing lightly in contact with the cover plate. It has to be like this otherwise the clutch pedal would be floppy at the start of its travel.

Your release bearing carrier sounds normal with an indent in one of its flanges to stop rotation. This does mean that the fork pins always operate in the same place causing wear and if excessive people have found ways to modify the carrier for example by putting an additional indent in it so that the pins are then held in a different place...

Thanks Johny. That’s clear. I suspect that’s my problem. I thought the clutch was stuck hard to the flywheel (after being laid up for 20’years) so I replaced it. But this wear would have the same affect - unable to disengage the clutch).
 

Putting an additional ident in so it sits in a different place sounds a good idea (except I’d have to take the gearbox out again!)

[Nick Whitehead]

17 minutes ago, NonMember said:

Yes, and that puts the release arm into the wrong geometry, so Nigel's washers under the slave may not work. The fix in this case is to put a washer or two under the mushroom pedestal that the arm rocks on. I was hoping this could be done in situ (because my GT6 has exactly the same problem with its new clutch) but it looks impractical and I'm going to have to get the 'box out again. Grrr...

Thanks. Good point. I’ll try the spacers on the slave and see if it works. If not, gearbox out! At least it’s now nice and clean…

Nick

[Nick Whitehead]

59 minutes ago, DanMi said:

There is a known issue with some of the release bearings supplied today being not the same thickness as originals

Thanks DanMi. I checked the new bearing to make sure it matched the thickness of the old one.

Nick

[Nigel Clark]

10 hours ago, NonMember said:

Yes, and that puts the release arm into the wrong geometry, so Nigel's washers under the slave may not work. The fix in this case is to put a washer or two under the mushroom pedestal that the arm rocks on. I was hoping this could be done in situ (because my GT6 has exactly the same problem with its new clutch) but it looks impractical and I'm going to have to get the 'box out again. Grrr...

My fix with spacers on the slave cylinder mountings does of course change the clutch release arm geometry slightly but it's worked fine on my car for 3,000 miles or more. 

Nigel

[Pete Lewis]

even with all the anomalies of the brg . carrier wear, push rod wear the pedal should give clutch clearance  

all the problems note all add up but i would start by clear all carpet from under the pedal 

push the slave right back inside the slave when bleeding as this has all the signals of air in the slave reducing its volume when bleeding helps 

make sure the bleed is in the top hole of the slave.

all the other snags are worth a follow up every little helps   but do the basics first 

old bearings are 19mm thick many new ones are 15mm thick  this needs a washer or two under the spherical post but thats a box off job

wear on the carrier or lever pins all contribute  but again its box off 

Pete

[johny]

10 hours ago, Nick Whitehead said:

Thanks DanMi. I checked the new bearing to make sure it matched the thickness of the old one.

Nick

Hmmm so this is now looking more like something isnt right with the assembly. Could the new friction plate be in the wrong way round or the new hydraulic components not be the right sizes? Also I take it the slave cylinder bleed nipple is uppermost with the pipe connected to the lower port?

[Iain T]

With regard to the carrier I drilled the flanges and pushed a 3mm rolled pin in to reposition the 'stop'. The pin is standard on most new carriers sold. Fortunately my arm pins were pretty good. 

Iain 

[Pete Lewis]

when it comes to bleeding its not uncommon the clutch pedal pivot is part seized  this stops the pedal fully returning and you dont seal off the reservoir  at the start of the  Mcyl stroke 

and check the Mcyl push rod  clevis for more wear 

Pete

[Pete Lewis]

some of the wear points 

pins can even be repalced if really bad 

some carriers have  roll pin some a dimple  easy to reposition 

this is to stop the carrier rotating and wearing the front cover

[Nick Whitehead]

On 12/05/2022 at 09:30, johny said:

Hmmm so this is now looking more like something isnt right with the assembly. Could the new friction plate be in the wrong way round or the new hydraulic components not be the right sizes? Also I take it the slave cylinder bleed nipple is uppermost with the pipe connected to the lower port?

Ah.... bleed nipple was on the lower port. Now fixed, thank you.

 

[Nick Whitehead]

On 12/05/2022 at 09:30, johny said:

Hmmm so this is now looking more like something isnt right with the assembly. Could the new friction plate be in the wrong way round or the new hydraulic components not be the right sizes? Also I take it the slave cylinder bleed nipple is uppermost with the pipe connected to the lower port?

I think I’m sorted. Most of the issue appeared to be a huge amount of wear in the coupling between the pedal and the master cylinder pushrod, meaning that for about half of the length of travel of the pedal, nothing was happening. The clevis pin was badly worn and the hole in the pedal it goes through was oval.

So after laying up for 20 years this car just completed it first 10 miles on the road. Brakes pulling badly, so that’s the next job.....

Thanks to to all who contributed to help me.

Nick

On 12/05/2022 at 09:38, Pete Lewis said:

when it comes to bleeding its not uncommon the clutch pedal pivot is part seized  this stops the pedal fully returning and you dont seal off the reservoir  at the start of the  Mcyl stroke 

and check the Mcyl push rod  clevis for more wear 

Pete