Slave Cylinder Discussion
Discussion
I know have four slave cylinders of different types sitting in pieces in my garage.
Three are original type and one is a raceproved. Interestingly all died the same way. The slave cylinder is a simple device it consists of three cylinders, an inner and outer which are fixed to the bell housing, and a middle which slides up between the inner and outer under the pressure of oil trapped between the inner and outer cylinder and supplied by the pressing your foot on the clutch.
The red oil seals seal the slave cylinder to the bellhousing.
The blue oil seals are the standard TVR ones, and the raceproved add a second yellow seal just to the inside as an extra precaution.
Appologies for the diagram and this isn't meant to tell anyone anything they didn't probably know already, but it is for a refererence for discussion.
All the slaves I'm looking at died in the same way. The innermost blue, or in the raceproved case blue and yellow seals disintergrated. This allowed the middle cylinder and the outer cylinders to touch. Obviously in the normal working model metal never touches metal as its always kept apart by the seals. If the seals die, metal touches metal the bores of the cylinders touch. The bores are forced back and forth while the oil is leaking over the floor under the car, and the bores get scored.
The death of the cylinder is not the seals as they could be replaced. The death is the metal on metal contact which scores the inner of the outer, or the outer of the inner. After that no replacement seal will work as they will simply be immediately destroyed by the scores. No real way of recovering after that.
One last point is that the original TVR slave is made out of stainless steel and the raceproved seems to be aluminium. I believe raceproved win for longevity by virtue of the second seal being a backup for the most likely seal to go and helps to stop the middle cylinder cocking to one side.
So to the discussion. I have one set of seals that look like they have overheated, and two sets which just look like they have dissovled. I assume its not that easy to overheat the slave as there is a big windpump spinning next to it, although the cats are nearby.
Two, does anyone know if the clutch fluid used might have an impact on dissolving the seals
And lastly all the seals I have are all the black rubber looking variety, is there any seal material which would fair better.
Three are original type and one is a raceproved. Interestingly all died the same way. The slave cylinder is a simple device it consists of three cylinders, an inner and outer which are fixed to the bell housing, and a middle which slides up between the inner and outer under the pressure of oil trapped between the inner and outer cylinder and supplied by the pressing your foot on the clutch.
The red oil seals seal the slave cylinder to the bellhousing.
The blue oil seals are the standard TVR ones, and the raceproved add a second yellow seal just to the inside as an extra precaution.
Appologies for the diagram and this isn't meant to tell anyone anything they didn't probably know already, but it is for a refererence for discussion.
All the slaves I'm looking at died in the same way. The innermost blue, or in the raceproved case blue and yellow seals disintergrated. This allowed the middle cylinder and the outer cylinders to touch. Obviously in the normal working model metal never touches metal as its always kept apart by the seals. If the seals die, metal touches metal the bores of the cylinders touch. The bores are forced back and forth while the oil is leaking over the floor under the car, and the bores get scored.
The death of the cylinder is not the seals as they could be replaced. The death is the metal on metal contact which scores the inner of the outer, or the outer of the inner. After that no replacement seal will work as they will simply be immediately destroyed by the scores. No real way of recovering after that.
One last point is that the original TVR slave is made out of stainless steel and the raceproved seems to be aluminium. I believe raceproved win for longevity by virtue of the second seal being a backup for the most likely seal to go and helps to stop the middle cylinder cocking to one side.
So to the discussion. I have one set of seals that look like they have overheated, and two sets which just look like they have dissovled. I assume its not that easy to overheat the slave as there is a big windpump spinning next to it, although the cats are nearby.
Two, does anyone know if the clutch fluid used might have an impact on dissolving the seals
And lastly all the seals I have are all the black rubber looking variety, is there any seal material which would fair better.
Judging by the colour of my clutch fluid, and the black gunk in the reservoir, I would say the most common cause of failure is that they dissolve. How crazy is that? Just imagine if they made the brake calliper seals out of the same stuff! Which begs the question why don't they use the same material? Interesting that you've had a RP one go. I would like my next one to be the last, obviously I'm not alone...
Edited by FarmyardPants on Saturday 21st April 12:59
Tis a very interesting point about the brake calipers. I've had loads of those apart although not all TVR. They all go the same way too. They nearly always sieze, and when you take them apart you see rusting of the bore.
I have never seen a brake caliper seal suddenly let go of all its oil, and yet they perform a near identical function to the slave.
I assume brakes go because the fluid isn't changed, and water is absorbed, or the brake piston is left too far out with a worn brake pad for too long and the piston or bore gets rusty. But none the less I've never had a brake seal disintegrate in the same way the slave cylinder ones go.
Either heat is a issue, or the fliud seal interacrtion is an issue. Can't think of anything else. None of the slaves I have in pieces have any rust issues where iswould influence their function.
Anyone know the actual difference between clutch fluid and brake fluid, Is there any?? AFAIK they come out the same pot in my garage.
I have never seen a brake caliper seal suddenly let go of all its oil, and yet they perform a near identical function to the slave.
I assume brakes go because the fluid isn't changed, and water is absorbed, or the brake piston is left too far out with a worn brake pad for too long and the piston or bore gets rusty. But none the less I've never had a brake seal disintegrate in the same way the slave cylinder ones go.
Either heat is a issue, or the fliud seal interacrtion is an issue. Can't think of anything else. None of the slaves I have in pieces have any rust issues where iswould influence their function.
Anyone know the actual difference between clutch fluid and brake fluid, Is there any?? AFAIK they come out the same pot in my garage.
There seem to be a few problems. Fist off the seal doesn't seem to be compatible with brake fluid, secondly the seals are not shrouded from clutch lining dust.
A vitron seal would help in regards the fluid incompatibility. A square section seal might help here as well, but you still have the problem that's it's all open to clutch dust.
http://www.tiltonracing.com/ins/98-1110.pdf
A vitron seal would help in regards the fluid incompatibility. A square section seal might help here as well, but you still have the problem that's it's all open to clutch dust.
http://www.tiltonracing.com/ins/98-1110.pdf
When i changed my slave cylinder and seals i assembled them with loads of red race-grease,this obviously lubricates the seals and appears to have done a good job as i did this over 4 years ago and so far so good.Also its worth while making sure that there are no burrs or sharp edges on the seal grooves.
However the seals in the master cylinders are a different story,im on my 3rd master cylinder in 6 years as the seals keep going in them!
However the seals in the master cylinders are a different story,im on my 3rd master cylinder in 6 years as the seals keep going in them!
Oooh, I love a good natter....
As long as everyone appreciates that I am a Dullo and have no training then I will give my thrupennyworth.
When my first Slave went (original TVR) my rantings with various peeps ont' 'phone revealed an intersting statement from Dave ( I think,...) at Clever Trevor who asked me what type of material my slave was made from. I hadn't a clue so said that it was heavy so Iron or Steel. He replied with 'Oh well, that'll be it then. Later Slaves were made all-alloy to stop the reactions between the metals from creating deposits which rubbed (and therefore broke-up) the seals'. Interesting, (in a Mr. Spock fashion) I thought.
At another time I also read that DOT 4 and DOT 5.1 liquids were created from different chemicals with quite different properties and I thought to myself 'Well, perhaps that was designed to resist heat failure but a reaction with the materials they work with could be an unexpected by-product'. Further food for thought.
The last time I rebuilt the Slave unit into the Bellhousing I was shocked to find that no chamfering of the edges that the seal had to pass over had been machined-in by the factory. I saw the fine layer that had been shaved off the seal on assembly and thought 'that's probably halved the working life of those seals'. Spoil the ship for a ha'penny-worth etc....
On Rog's mention of the contents of the Master reservoir: This time I had the failure, I took pictures and there was no breakdown of the chemical construction of the seal. It was in pieces, as if it had been actually torn or rubbed away.
On your point about brake seals though, I believe that they have a much tougher life with the ingress of every imaginable sort of filth that can be thrown up off the road surface and I can completely understand why they suffer corrosion and seal-surface attack but they generally do a far better job than TVR Clutch seals.
Like Esso I too, drowned the seal area in red grease but my last set lasted 12,000 - Just not built for purpose in my view.
After all this waffle I think that 5.1 is the best way to go BECAUSE of the heat build-up that occurs with the Bellhousing being nestled so cutely inbetween two catalysers running christ-knows what temperature.
I can easily believe that there is some, if only microscopic, build-up of reactionary material caused by incompatible materials working in close proximity under pressure and heat.
An amount of burr-removing from the (three) edges that seals pass over would
increase life several-fold
BUT
Why don't other performance-orientated vehicles suffer from this problem ?
My Suzuki is 23 years old, runs regularly at over 9000 rpm and still has the original Clutch.
My only deduction is that either the Factory or the Suppliers of the Seals just couldn't be bothered and thought "That'll give us an after-sales market".
The last time I talked to a technician at AP he was very indormative so I wonder if we should invite him in to give his views. They, after all, construct both the brakes and the clutches.
I rest m'case m'Lords.
As long as everyone appreciates that I am a Dullo and have no training then I will give my thrupennyworth.
When my first Slave went (original TVR) my rantings with various peeps ont' 'phone revealed an intersting statement from Dave ( I think,...) at Clever Trevor who asked me what type of material my slave was made from. I hadn't a clue so said that it was heavy so Iron or Steel. He replied with 'Oh well, that'll be it then. Later Slaves were made all-alloy to stop the reactions between the metals from creating deposits which rubbed (and therefore broke-up) the seals'. Interesting, (in a Mr. Spock fashion) I thought.
At another time I also read that DOT 4 and DOT 5.1 liquids were created from different chemicals with quite different properties and I thought to myself 'Well, perhaps that was designed to resist heat failure but a reaction with the materials they work with could be an unexpected by-product'. Further food for thought.
The last time I rebuilt the Slave unit into the Bellhousing I was shocked to find that no chamfering of the edges that the seal had to pass over had been machined-in by the factory. I saw the fine layer that had been shaved off the seal on assembly and thought 'that's probably halved the working life of those seals'. Spoil the ship for a ha'penny-worth etc....
On Rog's mention of the contents of the Master reservoir: This time I had the failure, I took pictures and there was no breakdown of the chemical construction of the seal. It was in pieces, as if it had been actually torn or rubbed away.
On your point about brake seals though, I believe that they have a much tougher life with the ingress of every imaginable sort of filth that can be thrown up off the road surface and I can completely understand why they suffer corrosion and seal-surface attack but they generally do a far better job than TVR Clutch seals.
Like Esso I too, drowned the seal area in red grease but my last set lasted 12,000 - Just not built for purpose in my view.
After all this waffle I think that 5.1 is the best way to go BECAUSE of the heat build-up that occurs with the Bellhousing being nestled so cutely inbetween two catalysers running christ-knows what temperature.
I can easily believe that there is some, if only microscopic, build-up of reactionary material caused by incompatible materials working in close proximity under pressure and heat.
An amount of burr-removing from the (three) edges that seals pass over would
increase life several-fold
BUT
Why don't other performance-orientated vehicles suffer from this problem ?
My Suzuki is 23 years old, runs regularly at over 9000 rpm and still has the original Clutch.
My only deduction is that either the Factory or the Suppliers of the Seals just couldn't be bothered and thought "That'll give us an after-sales market".
The last time I talked to a technician at AP he was very indormative so I wonder if we should invite him in to give his views. They, after all, construct both the brakes and the clutches.
I rest m'case m'Lords.
Edited by Mr Cerbera on Saturday 21st April 16:43
One other point is that the fluids contain swelling agents which expand but soften the seals. If you change the fluid to a different type then you are probably asking the seals to swell and soften a second time. Whilst i religiously change my brake fluid I never touch the clutch fluid and I have yet to have a slave cylinder seal go. Then again i have only had the Cerb 18 months but it is still on its original slave at 44k miles.
I'm not sure how much heat the slave has to put up with, not as much as the brake calipers(?)
Also, the clutch fluid isn't subjected to the same pressures as the brake fluid. High boiling point and resistance to being compressed are the major properties of (reasons for using) brake fluid. I do wonder whether some sort of oil could be used for the clutch instead.
Actually, Nick's comment about dust from the clutch might explain the black gunk. The wet slave piston would trap particles of friction material, which are then scraped by the seals and no doubt drawn into the slave (and fluid) when the pedal is released. Most cars have an external slave and activation arm - perhaps its contamination from clutch friction material due to it being inside the bellhousing that is the root cause. Changing the fluid regularly is said to prolong the slave's life (ironic given the location of the reservoir!)
Also, the clutch fluid isn't subjected to the same pressures as the brake fluid. High boiling point and resistance to being compressed are the major properties of (reasons for using) brake fluid. I do wonder whether some sort of oil could be used for the clutch instead.
Actually, Nick's comment about dust from the clutch might explain the black gunk. The wet slave piston would trap particles of friction material, which are then scraped by the seals and no doubt drawn into the slave (and fluid) when the pedal is released. Most cars have an external slave and activation arm - perhaps its contamination from clutch friction material due to it being inside the bellhousing that is the root cause. Changing the fluid regularly is said to prolong the slave's life (ironic given the location of the reservoir!)
Nickccc said:
There seem to be a few problems. Fist off the seal doesn't seem to be compatible with brake fluid, secondly the seals are not shrouded from clutch lining dust.
A vitron seal would help in regards the fluid incompatibility. A square section seal might help here as well, but you still have the problem that's it's all open to clutch dust.
http://www.tiltonracing.com/ins/98-1110.pdf
This is pretty much the cusp of it, seals not compatible with brake fluid... A vitron seal would help in regards the fluid incompatibility. A square section seal might help here as well, but you still have the problem that's it's all open to clutch dust.
http://www.tiltonracing.com/ins/98-1110.pdf
and the dust ingress. Viton would certainly solve most of the problems.A better system would use the dual seal arrangement of the Raceproved cylinder with a font dust seal as per 99% of road car applications these days.
I think the O-ring seal would be better combined with PTFE backing to support the inner cylinder within the outer. This way any thrust loading is supported by the PTFE and not squashing the seal and allowing the cylinders to contact.
Nickccc said:
From the Tilton pdf:E. Clutch Master Cylinder Priming
1. Prime the clutch master cylinder by filling the master cylinder reservoir with brake fluid. Do not use DOT 5, silicone based or high temperature resistant brake fluids designed for more than 550oF as some will cause the seals to swell.
I think I used ATE Racing Blue which is 280C/536F, wonder whether that was a good move.
I noticed that the first set of new seals, which I damaged when reassembling the slave, appeared to be better quality than the replacements that I finally used.
When I look at the garagefloor, I see litle black oil drops. Is this a sign of leaking seals??
The seals and perhaps the cilinders were changed, but from the beginning it showed these litle black oil drops. When I asked the garage, who did this, what they exaclty changed I didn't get a convincing answer and therefore I am not sure what they did.
I am now afraid eveything wil have to go of again.
Do I understand this right? When a raceproved cilinder (the complete thing) is changed, you stil have a good chance of early failure?
The seals and perhaps the cilinders were changed, but from the beginning it showed these litle black oil drops. When I asked the garage, who did this, what they exaclty changed I didn't get a convincing answer and therefore I am not sure what they did.
I am now afraid eveything wil have to go of again.
Do I understand this right? When a raceproved cilinder (the complete thing) is changed, you stil have a good chance of early failure?
I think I know what you mean. We did have an inspection once, because I was afraid that it was a leak from the crank seal. The engine had been overfilled with oil from the workshop. It wasn't from the crank though. Everything was put back (with al least new seals)and after collection of the car the drips were stil there.
flyingdutchie said:
I think I know what you mean. We did have an inspection once, because I was afraid that it was a leak from the crank seal. The engine had been overfilled with oil from the workshop. It wasn't from the crank though. Everything was put back (with al least new seals)and after collection of the car the drips were stil there.
A crank seal leak will normally come out between the bellhosuing and the block (or lack of on our engines at the bottom).Slave cylinder or Transmission input seal leak will come out between the transmission and the bellhousing.
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