Well, this solves a small mystery and solves a stupid problem.
My new slave (from XKS) pushes it’s piston towards the bottom and requires the long rod (from XKS).
When I replaced the slave cylinder on my '67,I was unable to get a proper adjustment. I added the spring and made a longer rod from a cut off bolt. I’m still not too happy with the shifting. Next time I mess with the adjustment I will try the 3/4"
Hello,
My name is Julian and I’m a Classic Cars French mechanic, currently working on a 1968 Jaguar 340 (# 1J80385DN), LHD, manual gearbox. I’m a little bit annoyed with the clutch.
When the engine is off, all the gears can be very easily engaged, but once turned on, it’s very difficult to engage any gears. The clutch is the default, no problem with that. But all the parts of the clutch system are new (coming from SNG Barratt) : clutch master cylinder, clutch slave cylinder, 3-piece clutch kit, hose). The clutch liquid (dot 4) has been drained and replaced. I have no leak…
According to the manual and the fact that the clutch slave cylinder is a hydrostatic type (I think ! See picture to confirm please), I respected the free-play and adjusted the rod length to obtain 19mm (3/4"). I bled the circuit as usually but without any result !!!
My questions
Should I use a longer rod, even with a hydrostatic slave cylinder ?
Should I bleed first and then adjust the rod length, or the opposite as I did ?
Does a special bleeding method exist with the hydrostatic slave cylinder ?
If your advice is to fit an external return spring, may you please join a picture ?
Thank you for your help.
Julian
I strongly recommend NOT using the hydrostatic slave, as it will lead to premature throw-out bearing failure. Instead, REMOVE the internal return spring, and fit the external return spring for an earlier or later car with non-hydrostatic slave. Then, make sure you do the periodic pushrod adjustments per the factory manual. If you insist on using the hydrostatic slave with the internal spring, you must NOT install the external spring.
Regards,
Ray L.
Thank you Ray for your answer. I’m not specially a hydrostatic slave cylinder lover ! I fitted this type of slave cylinder because it’s the original one.
SNG Barratt proposes the 2 slave cylinder types. Maybe it’s easier to return the hydrostatic one and exchange with a hydraulic type, rather than dismantle a new part to extract a spring…
Anyway, I will follow your advice and let you know.
Kind regards,
Julian
Julian:
FYI, the pic you show is a standard non-hydrostatic slave cylinder measuring 3 3/4" or about 95mm in length - see pic showing differences between the two types.
Good luck.
Gary,
You’re right when you say that my slave cylinder is 3"3/4 (95mm) but are you sure that’s a standard-non hydrostatic type one ? Because according to the SNG Barratt parts catalogue, it’s the hydrostatic one…
Has anyone get a picture of a hydrostatic slave cylinder… ?
The ONLY differences between the hydrostatic slave and non-hydrostatic slave are the length, and the internal vs external spring, and the pushrod length. Remove the internal spring, install the external spring, shorten or lengthen the pushrod as necessary, and the hydrostatic is functionally identical to the non-hydrostatic.
The set-up I have on my '67 FHC is as shown in this pic with the longer (3 3/4") slave cylinder and an external return spring.
I’m not absolutely sure if it’s factory correct or not as it’s possible it may have been converted from the short style cylinder by a previous owner. Free play is set at 1/16" and it works well in this configuration. 
I just replaced the slave cylinder on my 67 and have exactly the same configuration as yours. However, I did not remove the internal spring as Ray suggested, but as it is opposed by the much stronger external spring I cannot imagine that it makes any difference.
Rod
On my 1970 I needed to install a slightly stronger spring at the slave cylinder to get the throw-out bearing to separate from the clutch. With the stock spring it still would ride the bearing…Set the gap to 1/16" if I remember correctly.
Julian The clutch slave is very difficult to bleed - the inlet and bleed screws are on the “wrong” side of the cylinder for bleeding. I find it so frustrating that I’ve made new fittings to reroute the inlet to the bottom and the bleed on top. I strongly believe that this is why you are having a problem. Maybe somebody has a guaranteed method of bleeding this, but I can only suggest you try a vacuum bleed.
Incidentally I’ve used the hydrostatic slaves on my '68 E for years, and maybe 200k miles without issue. Mind you the clutch and bearing get changed periodically but never at mileage less than I think appropriate. Unless you’ve got a bad one from your supplier it’s not the equipment that is causing problems, and the rod, rod length and lack of external spring have nothing to do with your problem.
You should adjust the rod first, before bleeding, as you did.
Terry,
It’s exact ! It’s not the first time that I meet some trouble with bleeding a hydraulic clutch system ! And I’m not used to thinking that the equipment is causing problem but thrust me, it happens !
About this Jaguar 340, I’ve already modified the inlet rigid hose. So that, my bleed screw is on the top. No result any more. I haven’t used a vacuum bleed yet but why not…
If my current slave cylinder is not a hydrostatic type one as Gary affirms, so I think I will try to install an external return spring (easy job) and put in a longer rod (easy job too).
I will update you.
Kind regards,
Julian
1/16" gap with the standard slave cylinder, that’s it ? It’s very short, like 1.6mm…
There is a large ratio of moment arm length (the cylinder verses the pedal) at the pedal, so that 1/16 becomes a lot at the pedal. I tend to keep mine closer to 1/8, and just accept the larger free play at the top. Keep in mind as the clutch wears the gap will close up (although the release bearing wear will kind of make up for it), so you need to keep on top of it, although you can tell from inside the car, if the free play closes up you need to go adjust it.
The clutch hydraulics will typically self-bleed if you simply open the bleed valve, and walk away for about 15 minutes, then close the valve.
Regards,
Ray L.
1 Like
I’ve no doubt that works as too many people say it does. But, since the bleed nipple is on the bottom of the slave and air in the system rises, how does the air get out of the system? I’m assuming it bubbles up through all the piping and master to the reservoir.
I don’t know how it works, I just know it does.
Regards,
Ray L.
2 Likes
I reverse bled mine. Filled large syringe with fluid, connected it to slave bleeder, depressed syringe, close bleeder. I then checked the reservoir and there was some fluid in it. Filled reservoir and we had a clutch.
2 Likes
The hard pipe on the MGA is huge. Bleeding this is especially hard because air rises about as fast as you can tighten, release the pedal, open, push… Most of us reverse bleed it. Much less stressful and easier on the neighbor’s ears.