Failure of new clutch slave cylinder?

[Garth]

Alan and Graeme very kindly helped me put together my engine and gearbox yesterday - refurbished type 9 box on Sigma engine with new clutch, pressure plate and slave cylinder. All was going well (more or less!!) until we finished bleeding the clutch. The clutch pedal was very stiff and in pushing it very hard (probably should have realised something was wrong) there was a little pop as something burst! Fluid poured out onto the bulkhead below the master cylinder and also out of the bell housing.

Alan and I scratched our heads for a while (after cleaning up as much of the fluid as we could) and then closed the garage door in disgust and abandoned the car! 

We cannot think what might have happened? Either a faulty slave cylinder - or pressure plate somehow stuck so slave cylinder could not budge it? Or is there something else we should have done? Clutch and pressure plate replaced by a very reputable Caterham man!

Guess it is a new master cylinder too? Where is the best place to get one?

Planning to get it back out tomorrow morning to inspect.

Any thoughts most welcome.....

Thanks

Garth

 

[Jonathan Kay]

Guess it is a new master cylinder too? Where is the best place to get one?

I'd try Redline first.

Jonathan

[Garth]

Cheers Jonathan

[Shaun_E]

If it's the same/similar slave cylinder as used on Duratec cars then if you over extend it then it will go pop - it goes hard just before this point. A clutch stop is essential.

[john milner]

If it is the master you might be able to buy a recon kit that replaces all the seals.

When the seals went on my master (K Series-Type 9) it was only a few months and the slave went as well. I put it down to one part being brought up to full strength killing off the other although it could be just coincidence.

[ChrisC]

The connection between slave and the braided hose is only a push fit with a clip, could it have become unclipped?   Its not the same slave as the duratec cars, but if its failed its the same engine out result. 

[Alan Reeves]

The start was bleeding the lines and that expelled the air. Close the nipple and and it produce a severe pressure at the peddle.

pressing really hard obviously sends that pressure through the lines and hence a burst system.

does that indicate that the slave was stuck hard and not moving and hence causing over pressure in the lines.

what would cause the slave to not activate , the lack of a peddle stop during the bleed cycle ? Not sure if there is one on Garth’s car

Painful 

 

[Garth]

Shaun - I responded to your over extension comments, but must have failed to hit the post button! The clutch pedal was very stiff - almost brake like - from the very top of the travel. It was also a like for like replacement so I am assuming the travel should be much the same as before - unless I am missing something?

Hi Chris - my braided hose has a threaded connection into the slave and banjo onto master - so no chance of popping off!

I think there is a clutch stop on my car Alan - will check tomorrow when we get it out! Hopefully all will be revealed, but still a bit of a mystery to me!

[7 wonders of the world]

There should be no need to pump the pedal for bleeding as you can simply use gravity, open the nipple and wait - job done nice and easy.

CSC are sensitive to correct fitting height which should be checked for each application to prevent over extension, sounds like you have pumped it too much to bleed and indeed you have taken it beyond its permitted travel.

Unlikely you will need a new master though, as the fluid displaced here will be as a result of the CSC piston being sprung back into its rest position albeit minus a working seal - hence fluid loss via the bellhousing, its an arse as it will be an engine out job I'm afraid.

I do run a clutch stop too, I set mine short and adjusted until I gained sufficient clearance to eliminate any clutch drag

[Garth]

Have had the engine out and checked everything. Slave looks ok - some fluid looks like it came out of the connection between the slave and the hose or bleed nipple. The new slave is about 10mm longer than the original when fully compressed, so I think this is the problem? When fitted it was likely fully compressed against the pressure plate and in its fully compressed state it will not extend because fluid paths are blocked? 

Difficult to see how it can be over extended whist bleeding as the fluid will take the path of least resistance and simply flow out of the bleed nipple?

Have had the master cylinder out and it looks as though the only place the fluid could have come out was the banjo connection as seal around piston is dry and any fluid coming from here would have ended up in the foot well (there was no sign of fluid here!).

Looking to source a ford slave cylinder identical to my original.

I do have a clutch stop and will be adjusting it carefully!

Thanks

Garth

[Ian Mackenzie]

Hi Garth

There will only be around 10mm travel or less to release the clutch with the slave. So if the new one was 10mm longer is will of been the same as the old one at full stroke, only with no pressure. Most likely is the new one was now fully compressed and jammed with no mechanical movement left, hence the firm pedal. The other thing to note is the concentric slaves do not like being compressed before the are installed as you can damage the seals. Cheers Ian

[Garth]

Thanks Ian - very helpful - am now trying to source the correct slave. Garth