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I have been chasing a niggle with the clutch on my 1961 2.4 since I got it home. I am not happy with the operation on the hydraulic side, and currently cursing a lack of data! In brief, the biting point is either very high, or is slightly variable.
The potted version is the car has 37000 miles from new, a new clutch was put in back in 1995, mileage since then is around 2500 miles, 750 are what I have put in since May. I checked the clutch fluid and as it was pretty dire (black sludge at the bottom of the reservoir) I have stripped the hydraulics down, honed the bore on the slave and replaced the seals to eek a few more months out of it for the summer, and replaced the seals in the master cylinder, There was some seepage in the slave, and no sign of a leak from the master at all. Back in 1995 the garage fitted the later diaphragm clutch, along with a long type slave cylinder, fitted with the original return spring on the outside. The casting for the slave is marked as 3232-648C,which I believe is the later non-hydrostatic slave (C29801). This was when the car was with the previous owner.
Thanks to the bargain £40 Lidl inspection camera I have been able to look inside the bell housing to see it is definitely the diaphragm clutch, and the release bearing looks to be in good condition with little wear. The iron part is painted so I am pretty sure it is the correct matching one for the diaphragm clutch (type HD1099 according to David Manners website). I am pretty confident there are no problems in the clutch itself, as unless someone has driven riding the clutch continually before I took on the car I find it hard to belive the friction plate can have been worn out in less than the routine adjustment mileage!
Since I flushed the system (thoroughly with methylated spirit as per the service manual) and replaced the seals the clutch operation is less mushy, but the biting point varies a little before currently settling close to the top of the pedal. Beforehand it was feeling like it was dragging a little at times, and gets a fair amount of judder after a longish drive on a hot day in first and reverse. The variation in biting point I can put down to the condition of the slave bore even after honing and seals, but the high biting point is more of a puzzle.

The questions are:

1: Does anyone have accurate measurements for the different operating rods? Specifically for the short cylinder, and for the later non-hydrostatic cylinder, and whether this is just the rod itself or including the adjustable fork part.

2: Does it matter which cylinder is used with the diaphragm clutch, or is it irrelevant as long as the correct operating rod is used?

3: Which free play adjustment should I be working to: the 3/4" at the pedal as in the manual for the early cylinder, or the 1/16" at the operating rod and fork as in the service bulletin for the long non-hydrostatic cylinder? I am struggling to tell what the free play at the pedal is , as I am more used to setting up cable clutches. There is currently a bit of rattle room on the pedal and the release fork (close to the 1/16" in the bulletin), but for the pedal are we talking about the light resistance felt before the slave actually moves the fork?

I am pretty much decided that the current slave will be evicted and a new one fitted sooner rather than later, but I am loath to order a new one before I know whether to order the same one as I have now, or to return it to the orginal short cylinder. A new flexible hose will be going in on the order just to be on the safe side, but I'd rather order once and order right than end up chucking parts at things!

Hello Pegasus,

the diaphragm clutch should not use the return spring on the slave cylinder. The hydrostatic cylinder automatically adjusts itself as the clutch wears and the piston is not designed to return to the bottom of the cylinder, hence the extra length. Adjustment of the push rod should also not be required as it self adjusts.
Try removing the spring and see how you get on?

Alec

Hi Alec,
As far as I can tell after digging through stuff the cylinder on mine is the latest type one, which is the longer length, but was after Jaguar abandoned the hydrostatic setup and went back to a return spring. The information is quite muddled when you can find it, but it seems that the 3232-648C is this type C29801, and 3232-648 is C14145, the hydrostatic one, and the only difference is the type of spring fitted inside the cylinder. I assume it is thicker gauge to keep the cup and piston part way along the bore, whereas the other is thinner and only there to keep the cup and follower straight in the bore. A lot of what information is available is from E-type forums rather than saloon owners, but the part numbers mostly coincide with the Jaguar bulletins, specifically the 1968 one referring to the abandonment of the hydrostatic cylinder. I've pretty much settled on replacing the cylinder but the operating rod length is the thing I need to check as I would order the correct cylinder to suit the one currently fitted. I just don't know if the rod on mine is the original short cylinder one or the later one to suit the longer cylinders. The bulletin suggests the same rod works with both longer cylinder types, but as mine started off with a coil spring clutch it isn't that simple. As it was changed in 1995 I would assume the problems with the hydrostatic cylinder would have been well known, and that they fitted the non-hydrostatic one. Certainly the spring in the bore shows no willingness to move the cup and cylinder towards the open end at all with or without fluid behind it!

James

Hello James,

if the clutch is operational, which it sems to be I wouldn't bother replacing the slave cylinder. (judder may be engine mounts rather than clutch).
The spring will confuse what set up you now have and without it the pedal should eventually settle down and feel normal. There will be very little free play between the push rod and the fork but you should be able to force the push rod and piston back down the cylinder. If that amount of movement is small (1/4" or so) I would leave it, if very much longer, extend the push rod adustment. The short clearance will allow the piston to slowly go further into the cylinder as the clutch wears. If that clearance is lost there will possibly be tendency for the clutch to slip, just as if you had the clutch pedal depressed a short distance.

Alec

I wondered if Alec and James had anything to add after 4 years.
The clutch on my car started getting very hot and refusing to disengage. I discovered the flexible rubber section had started to leak more and more. Anyway that will be replaced in the next few days. I am torn whether to set up the 1/16th clearance with the return spring or the 3/4 clearance with no spring.
Other cars I have had with a graphite bearing all used the 1/16th clearance with a return spring to pull the graphite face away from the clutch cover, in normal driving. I always thought that was the way to do it.
A post on another forum suggested the 3/4 clearance was all about making it maintenance free. Presumably at the expense of release bearing wear.
Peter