Another slave cylinder gone
Discussion
The dreaded drip has appeared below the bell housing.
Its been moist for a while, but now I think it's time to change it.
The clutch operates perfectly but don't want to get stranded.
I've been spending too much time on other cars, so the Cerbera has thrown a wobbly!
So, how difficult is it to change it? I'll go for the race proved one from TVR parts. Is it as simple as pulling the gearbox off the bell housing and unbolting the slave and replacing or are there connections in the bell housing that have to be got to?
Thanks
Its been moist for a while, but now I think it's time to change it.
The clutch operates perfectly but don't want to get stranded.
I've been spending too much time on other cars, so the Cerbera has thrown a wobbly!
So, how difficult is it to change it? I'll go for the race proved one from TVR parts. Is it as simple as pulling the gearbox off the bell housing and unbolting the slave and replacing or are there connections in the bell housing that have to be got to?
Thanks
As you can see I always drop the delicate manifolds before attempting to remove the gearbox, but no one else does.
Removing the gearbox is the difficult part, the rest is relatively easy. But there are two steps that I ignored which cost me big time. I didn't replace the pilot bearing (spigot bearing), and I didn't re-shim the gearbox input shaft - total consequential loss was around £2k.
Removing the gearbox is the difficult part, the rest is relatively easy. But there are two steps that I ignored which cost me big time. I didn't replace the pilot bearing (spigot bearing), and I didn't re-shim the gearbox input shaft - total consequential loss was around £2k.
There really is no need to remove the manifolds, or prise them open to remove the gearbox.
You just need to get the car high enough first and obviously remove the bell housing.
As for slave, I'd fit a clutch stop to the pedal to ensure you don't over-stroke the slave first before considering major surgery. Plus I'd make sure the step on your flywheel is high enough as it does wear.
If you haven't over stroked the slave and your flywheel is ok then (outside of an off perpindicular engine and bellhousing mating) excessive heat is another cause of slave failure, which can be countered by reducing the heat radiated from the headers with ceramic coating or wrap.
Plus I always put a dab of good moly grease in the pilot bearing while I'm there, however if you don't have a recently rebuilt gearbox (which I have) I suspect spigot play due to worn shims might suggest replacing the pilot bearing a really good thing to do as well.
You just need to get the car high enough first and obviously remove the bell housing.
As for slave, I'd fit a clutch stop to the pedal to ensure you don't over-stroke the slave first before considering major surgery. Plus I'd make sure the step on your flywheel is high enough as it does wear.
If you haven't over stroked the slave and your flywheel is ok then (outside of an off perpindicular engine and bellhousing mating) excessive heat is another cause of slave failure, which can be countered by reducing the heat radiated from the headers with ceramic coating or wrap.
Plus I always put a dab of good moly grease in the pilot bearing while I'm there, however if you don't have a recently rebuilt gearbox (which I have) I suspect spigot play due to worn shims might suggest replacing the pilot bearing a really good thing to do as well.
aide said:
If you haven't over stroked the slave and your flywheel is ok then (outside of an off perpindicular engine and bellhousing mating) excessive heat is another cause of slave failure, which can be countered by reducing the heat radiated from the headers with ceramic coating or wrap.
I think you've nailed it there. The failure is most likely heat related, which is one reason why my car is decatted, that and not wanting to have to wear gloves to change gear.I am more suspicious about the over stroke issue, I really don't see that being a clutch travel problem, there has to be something else going on there. Finger failure is stress related, not a minor adjustment issue.
Edited by ukkid35 on Wednesday 5th October 22:29
ukkid35 said:
aide said:
If you haven't over stroked the slave and your flywheel is ok
I am more suspicious about the over stroke issue, I really don't see that being a clutch travel problem, there has to be something else going on there. Finger failure is stress related, not a minor adjustment issue.Over stroke and finger failure are independent issues.
Putting over stroke to one side (as a pedal stop solves this issue) I should have been clearer when pointed out that the step on your flywheel (or lack thereof due to wear) means that the fingers on the clutch diaphragm naturally rest further away from the clutch plates, when fully engaged, and thus require A LOT more force to move themwhile disengaging the clutch. This extra force, required to disengage a clutch diaphragm mounted on a flywheel with a worn step, means that the slave seals and fingers shoulder load. And put excessive stress on both the slave seals and diaphragm fingers.
In short, the flywheel step is crucial, if it's too low then the resting position of the diaphragm fingers protrudes too much, requiring great effort to move them.
I had long telephone and email conversations with the guy that designed the RP slave once upon a time and he kindly explained this.
Actually, here's an email I sent to Russell Hinton a few years ago, summarising the ideal RP slave installation he described to me over the phone.
Hi Russ
Many thanks calling me and sincere thanks for all your advice.
Summary of tolerances:
-o- Flywheel step must be > 2.5mm
-o- Uncompressed Clutch plate should be between 7.2 and 7.6mm
Cleaning and installation:
-o- Use (red) Scotchbrite and brake cleaner for slave to bellhousing mating surfaces
-o- Fisrtly apply grease into the gap where the small seal resides and then place the seal in.
-o- just put four dots of grease on the big seal to secure it
-o- Lower the slave into the bellhousing and in a clockwise fashion use the four bolts (with a half turn each time) to slowly push the slave into place.
Flywheel pilot bearing and spigot splines:
-o- Clean the pilot bearing, make sure it’s dry, apply lithium grease and roll it around. Then remove any excess.
-o- paint the spigot shaft with copper grease and then wipe off any excess so that you only leave a film of grease in the splines.
Hi Russ
Many thanks calling me and sincere thanks for all your advice.
Summary of tolerances:
-o- Flywheel step must be > 2.5mm
-o- Uncompressed Clutch plate should be between 7.2 and 7.6mm
Cleaning and installation:
-o- Use (red) Scotchbrite and brake cleaner for slave to bellhousing mating surfaces
-o- Fisrtly apply grease into the gap where the small seal resides and then place the seal in.
-o- just put four dots of grease on the big seal to secure it
-o- Lower the slave into the bellhousing and in a clockwise fashion use the four bolts (with a half turn each time) to slowly push the slave into place.
Flywheel pilot bearing and spigot splines:
-o- Clean the pilot bearing, make sure it’s dry, apply lithium grease and roll it around. Then remove any excess.
-o- paint the spigot shaft with copper grease and then wipe off any excess so that you only leave a film of grease in the splines.
Agree with removing the manifolds, can't see how you could get the bell housing or gearbox out without a lot more messing around and potential for braking things.
As far as slaves go, agree they seem problematic but I think that if the rebuild is done correctly and everything is clean, flat greased and no sharp edges they last well.
Mine had done 35k on the original s/s slave before it needed replacing. What I could see was an abovious cause of failure was the inside of the bores had machining grooves and has never been polished or honed. This meant the seals were effectively being grated.
Even when I replaced the slave, I took it apart and checked, sanded & polished all the surfaces with even a slight imperfection.
As far as slaves go, agree they seem problematic but I think that if the rebuild is done correctly and everything is clean, flat greased and no sharp edges they last well.
Mine had done 35k on the original s/s slave before it needed replacing. What I could see was an abovious cause of failure was the inside of the bores had machining grooves and has never been polished or honed. This meant the seals were effectively being grated.
Even when I replaced the slave, I took it apart and checked, sanded & polished all the surfaces with even a slight imperfection.
Hi Ian, 
It’s easy (Says Mr. Dullo). Manifolds can stay on. I jiggled my gearbox off on a wheeled car jack and there was plenty of room.
There is quit a bit of jiggery-pokery with extensions to get the gearbox off (and I used Allen keys with rounded ends to make things easier)
DON’T, under any circumstances, depress the clutch (and therefore misalign the twin plates) whilst the gearbox shaft is out. I used a “borrowed” gearbox shaft to ensure that there was alignment.
As Aide says, when you reassemble try to ensure that the pedal depression is at max when the clutch disengages to prevent over-stroking it and causing future finger failure.
Here’s my experience(RIP Mad Mark)
HTH
It’s easy (Says Mr. Dullo). Manifolds can stay on. I jiggled my gearbox off on a wheeled car jack and there was plenty of room.
There is quit a bit of jiggery-pokery with extensions to get the gearbox off (and I used Allen keys with rounded ends to make things easier)
DON’T, under any circumstances, depress the clutch (and therefore misalign the twin plates) whilst the gearbox shaft is out. I used a “borrowed” gearbox shaft to ensure that there was alignment.
As Aide says, when you reassemble try to ensure that the pedal depression is at max when the clutch disengages to prevent over-stroking it and causing future finger failure.
Here’s my experience(RIP Mad Mark)
HTH
Edited by Mr Cerbera on Saturday 8th October 15:52
Finally got to take the cerb out after a few months of hibernation. It has left me stranded with no clutch. Luckily I was near a petrol station so pushed it onto the forecourt and bled it but it's FUBAR. Hardly any resistance on the pedal. Got lots of air out and clean fluid coming through but half of it is under the car so looks like time for another slave 
This is two months after I cancelled my AA membership, too. I had the parts and labour policy, euro cover, the lot, but it was £500 a year so I canned it and went for green flag. Bad move. I'm going to have to pay £120 for excess mileage on the recovery, plus the P&L policy would've paid out £475 towards the repair. Doh!
Is the raceproved slave worth getting or is that just as bad?
This is two months after I cancelled my AA membership, too. I had the parts and labour policy, euro cover, the lot, but it was £500 a year so I canned it and went for green flag. Bad move. I'm going to have to pay £120 for excess mileage on the recovery, plus the P&L policy would've paid out £475 towards the repair. Doh!
Is the raceproved slave worth getting or is that just as bad?
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