Clutch Slave Cylinder Piston Replacement

[Tommd55 (Tom D)]

@Michael_Frank

All hydraulic systems are hydrostatic.

True, but not what the term hydrostatic is referring to. It is the adjustment that is being referred to as hydrostatic. (Didn’t we address this before. )

@Michael_Frank

Again, complete nonsense. All hydraulic systems are hydrostatic. With the self-adjusting system, the self-adjustment is powered by the clutch springs, not the hydraulics. The clutch springs push back on the release plate, which presses back on the release bearing, which pushes back on the lever, which causes the piston to retract, which pushes fluid back up to the master and on to the bottle. The release bearing can never lose touch with the plate, because all the force is supplied by the clutch. There’s nothing hydraulic or “hydrostatic” to maintain the adjustment. They supplied a thicker bearing to compensate for the extra wear, and that was that.

One can define things as one wishes, but I have trouble following your disagreement. However, the reason for adjustment routine on the non hydrostatic is because as the clutch disk wears, the 1/16" free play decreases. If it decreases too much it approaches 0 inches, and then goes to the point that the pressure plate is actually being slightly pushes, eventually causing the clutch to slip. So to prevent clutch slipping, one must readjust some clearance into it by manually and mechanically adjusting the push rod. On the hydrostatic system it is not initially adjusted to 1/16" free play. The rod/piston is pushed back to bottom out. Then manually mechanically adjusted initially to 3/4 inch free play. When one presses the pedal, the fluid pushes the TOB to the PP, and released, as you said, the PP pushes the TOB, rod, and piston back only to the 0 inch free play. And it will remain there until/as the clutch disk wears. As it wears, the TOB, rod and piston are all pushed back into the cylinder just a little bit further. When it moves 1/16 of an inch that is no problem as it just simply pushes more fluid back into the slave to keep the 0 free play, but no clutch disk slippage. So rather than someone manually mechanically adjusting the push rod to gain the 1/16 inch free play on the non hydrostatic system, on the hydrostatic system, the 0 free play is maintained automatically by less fluid in the cylinder. Thus automatic hydrostatically adjusting.

@Michael_Frank

self-adjustment is powered by the clutch springs,

Okay, yes it is powered by the clutch springs, but the adjustment is taken up by, thus adjusted by, the change in fluid volume in the cylinder rather than the length of the push rod.

@Michael_Frank

There are any number of ways you can screw up the adjustment and end up with an engine-out exercise to replace that fifty dollar part.

Agreed, but if one follows the manual, that is seldom a problem.

@Michael_Frank

he discussions here and on other lists revolve around pedantic positions based on nothing but guesswork, misinterpretations of the FSM, part numbers, and personal opinion.

100% agree, which is why I do not understand why everyone keeps trying to do it different. Choose one of Jaguar’s two methods and stick with it. I, like many do prefer the non hydrostatic.

@Michael_Frank

because the bearing ALWAYS drags on the disc face.

Does it? I do not have the evidence, but I would not be surprised that by the time one takes into account the crank end play, flywheel runout, PP runout that the TOB may actually be pushed back far enough to actually no longer be actually dragging. Maybe skimming? I am not sure the internal slave spring is strong enough to overcome the piston seal friction. If it is, then just minimal drag.

@Michael_Frank

calling it “hydrostatic” has led generations of mechanics into mistakenly believing that it was hydraulically adjusted.

Again, per Jaguar’s and the entire automotive industry, it is considered to be automatically hydraulically adjusted.

@Michael_Frank

I lay under my car for three days experimenting with seals, springs, rods, pistons and adjustments.

With all due respect, that was your choice. You could have done it without trying to change everything around. You could have chosen to do it Jaguar’s way in been done in a reasonable amount of time. Your choice, not a Jaguar issue.

@Michael_Frank

If the idea is to minimize wear on the hard-to-replace bearing,

I am not completely disagreeing with you here. But Jaguar’s goal was to avoid excessive pressure on the PP to avoid clutch slippage. I believe in their minds, the TOB was NOT the problem. After all, keep in mind, as the clutch is used, the clearance, per what others have previously posted, and I agree, the free play decreases. If the TOB was wearing, the free play would increase. Thus the clutch disk was wearing out faster than the TOB. TOB was not their issue. We have made the TOB the issue.

@Michael_Frank

As for what amount of free play is right, if you view my video…

Not sure how a worn system is relevant. My assumption is that typically the linkages will outlast a clutch disk. and at the point of replacing the disk, then all other worn parts should be addressed.

Tom

[ryaskovic (Rob Yaskovic '68 S1.5 OTS)]

A link to a post from 18 years ago from Dick V on some model and hydrostatic and non-hydrostatic clutch slave part information -

[E-Type] Re: 1967 Slave Cylinder Replacement II

Hello Chuck, The earliest clutch slave cylinder (used on all 3.8) was a non- hydrostatic model detailed as follows: C.16989 Complete Slave (110272) 8335 Body casting 8336 Spring (89500) 6139 Cup filler (87575) 8591 Seal, Piston (27526) 8592 Piston (103439) 8337 Circlip (K.19714) 6142 Rubber boot (33427) 6096 Bleeder screw (28696) 8593 Repair kit (SSB-601) C.9798 Operating rod (4.25" according my notes) C.10360 Adju…

I’m lucky my time machine worked…my hydrostatically non-hydrostatic flux capacitor is on the fritz!!

RobY

[davidxk (David Langley)]

Some data points concerning the serial numbers concerning the clutch release bearing, and hydrostatic clutch slave.

SPB C.11 dated May’64 Intro of 10" Laycock diaphragm spring clutch at Engine # RA.5801 (during 3.8 period). Introduced new release bearing C.22478 (82975/2) - replacing P/N 6840 (48444)

SPB C.15 dated Sept’65 Intro of Self Adjusting Clutch (hydrostatic slave) at Engine # 7E4607 (during S1 4.2 period). No change to the release bearing

SPB C.24 dated Jul’68 intro of 9-1/2" Borg & Beck diaphragm Spring clutch (replacing Laycock) at Engine # 7E13501 (2+2 7E53582) (during S1.5 period). Introduced new release bearing C.23575/1 (78261) - replacing C.22478.

At unspecified date, re-introduction of Manually Adjusted Clutch (with external return spring) at Engine # 7E18356 (2+2 7E55558) (during S1.5 period). No change to the release bearing.

At the introduction of the Series 2, the Borg & Beck diaphragm clutch was still the standard part, as was the C.23575/1 release bearing. The slave cylinder was now C.29801 which was not self-adjusting, and used the same external return spring as the earlier cars.

So, in conclusion, the change in release bearing seems to only be associated with the change in clutch pressure plate, and not with the clutch slave. The period of the self-adjusting clutch (which Jaguar called Hydrostatic) was from fairly early in the S1 4.2 period ([edit]spring fall 1965 ) through to late in the S1.5 period (summer 1968).

I trust that this post is totally devoid of

@Michael_Frank

pedantic positions based on nothing but guesswork, misinterpretations of the FSM, part numbers, and personal opinion

[Wiggles (Paul Wigton)]

@davidxk

The period of the self-adjusting clutch (which Jaguar called Hydrostatic) was from fairly early in the S1 4.2 period (spring 1965) through to late in the S1.5 period (summer 1968).

What were production numbers during that period (how many cars were made)?

[Ray_Livingston]

David,

Good information! So, as I suspected, the throwout change has to do with the pressure plate change, not the hydrostatic slave. But, there are now THREE throwouts?? One for the spring clutch, one for the Laycock, and another for the B&B? First I’ve heard of that! I wonder how the Laycock throwout differs from the B&B? Thicker or thinner? Probably kinda moot, since I have never even heard of a Laycock replacement clutch in over 20 years of E-Type driving.

@davidxk

The period of the self-adjusting clutch (which Jaguar called Hydrostatic) was from fairly early in the S1 4.2 period (spring 1965) through to late in the S1.5 period (summer 1968).

I think that should be fall 1965, rather than spring, no? You earlier gave the introduction date as Sept '65.

7E18356 is very close to the end, if not THE end, of S1.5 production.

[davidxk (David Langley)]

@Wiggles

What were production numbers during that period

Don’t forget that in addition to the E-Type, other Jaguar models went through the same slave cylinder dance. The 2.4, 3.4, and 3.8 Mark 2, and 3.4 and 3.8 S-Types were all affected. I don’t have any numbers, but based on the E-Type engine numbers you would think that (18356-4607)+(55558-50001) E-Types would have had the hydrostatic slave, that is 19306.

[davidxk (David Langley)]

@Ray_Livingston

But, there are now THREE throwouts??

Yes. I’m pretty sure I’ve seen photos of all 3 side by side somewhere.

@Ray_Livingston

I have never even heard of a Laycock replacement clutch in over 20 years of E-Type driving.

Me neither.

@Ray_Livingston

I think that should be fall 1965

Correct. I was remembering the May’65 date, but was for the Laycock diaphragm clutch. My mistake. I will correct my post in case it is used for reference in future.

@Ray_Livingston

7E18356 is very close to the end, if not THE end, of S1.5 production.

Agreed. 7E18372 is the latest I’ve found on xkedata, so it is, to all intent and purpose the end of the S1.5s

[Ray_Livingston]

Nice to finally get to the bottom of the story on the different variations of throwouts!

[robrien24 (Rick OBrien)]

@Ray_Livingston

Nice to finally get to the bottom of the story on the different variations of throwouts!

It seems you guys have a pretty good handle on the correct clutch/slave/TO combinations. So I’m hoping you can help me out.

A million years ago when I thought my powertrain would be restored any day now, I bought a new cover, clutch and TO bearing from Gran Turismo Jaguar. I would now like to use them as NOS. I also recently had White Post restore my slave. I’d like to verify I now have a workable combination.

The car is 1E30148 (very early 1965 4.2 FHC, build date Oct 1964. The engine is 7E1369-9. It is likely the old clutch I removed is not original to the car since it had 90k miles in 1978 when I bought it, and was on its second transmission (KE instead of the original EJ).

Here is the slave, most likely original. WP substituted a different boot. Hopefully it’s OK.

Here are the NOS cover and clutch with inset box labels:

Note the clutch is a Laycock apparently intended for a diaphragm spring cover but I remember GTJ saying it would work fine for the coil spring version, as long as both were 10".

And here’s the NOS TO bearing compared to the one I removed from the car. They don’t match. But I don’t know which is right (if either one of them is). When I took the car off the road, the clutch had no free pedal and engaged very high. So something was amiss.

Incidentally, the clutch/cover I removed looks just like the new NOS parts. But the TO bearing is suspect. It is larger than the old one and has a different pivot offset. It is also larger, barely passing thru the fork.

So what do you think?

Thanks
Rick OBrien
65 FHC in FL

[Ray_Livingston]

ANY slave cylinder will work, provided you do not try to duplicate the (failed) self-adjusting feature of the “hydrostatic slave”, and use a string external return spring. You may, or may not, need to lengthen, or shorten, the pushrod, depending on which one you have. With the spring pressure plate, you need the thinner (in your case blue) throwout. DEFINITELY test that you can fully release the clutch BEFORE re-installing the engine in the car.

[Michael_Frank]

Question: I see the replacement slave laid out with the external spring on the top bolt. Mine, and most of the ones I’ve seen, have the spring mounted to the bottom bolt. The significance is that the pin would be reversed. That would make it much easier to install the clip, but much harder to install the spring. I’m also not sure if there’s clearance to install the pin upside down. Anyone played with this, and care to comment?

[Marco (Mark)]

Yes. The installation can be done either way but difficult to stretch the spring when it’s on top. If I recall my logic was to keep the retainer clip on the bottom so if it failed gravity did not pull the pin out but kept it in.
Classic case of me overthinking things…

[robrien24 (Rick OBrien)]

@Michael_Frank

Question: I see the replacement slave laid out with the external spring on the top bolt. Mine, and most of the ones I’ve seen, have the spring mounted to the bottom bolt. The significance is that the pin would be reversed. That would make it much easier to install the clip, but much harder to install the spring. I’m also not sure if there’s clearance to install the pin upside down. Anyone played with this, and care to comment?

I just wasn’t paying attention when I took the photo. I plan to install it the conventional way. I may also use coarse threaded SHCS instead of the studs and nuts. My pin is badly butchered and should be replaced but the current photos seem to be missing the spring perch. Generic photo maybe? Or do I have the wrong P/N?

[davidxk (David Langley)]

That’s the pin from the earlier cars without the “turret” for the spring. With that version the spring just hooks over the pin and a washer/split pin stop it coming off. Lots of discussion on another recent thread - Adding a clutch return spring - Parts? - #2 by Ahwahnee

[robrien24 (Rick OBrien)]

Ah, now I see. I seem to have the setup from a later car, perhaps the one where my KE tranny was harvested from. At any rate, the whole assembly is pretty bad so replacing all of it is in order. I do like the SNGB design better than what was original for my car. I notice none of the repros have the bronze bushing in them that I have, but who’s kidding who…I’ll never wear this part out!

Thanks for the insight
Rick

[Les_Halls (Les Halls 1968 S1.5 2+2 Atlanta)]

Apologies for jumping in here with a question that just might have been answered, although I didn’t see it…anyway…

I have a '68 S1.5. It appears that Jaguar used two types of slave cylinder…hydrostatic (no outside return spring but has an internal spring) which I believe I have on my car, then later on went back to what I believe is the original type (outside return spring and no internal one). My question is…when changing out a leaky or old hydrostatic device, which is the best type to replace it with and is a new adjusting/actuating rod required?

Thanks in advance.

[Michael_Frank]

First of all, after much fiddling, I’ve come to the conclusion that Jaguar was in error when they called these hydrostatic cylincers. All hydraulic components are hydrostatic, there’s no distinguishing characteristic that makes these “more” hydrostatic than the next slave cylinder design. Lockheed’s more accurate term for these cylinders is self-adjusting vs non self-adjusting. The self adjusting cylinders allow the throw out bearing to rest against the release plate at all times. The manual adjusting cylinder uses an external spring to pull the bearing away from the release face by a little bit. Given the extraordinary cost to R&R the engine and transmission, I’d go with the non self-adjusting system. Saving even a little bit of wear and tear on the throw out bearing is worth the effort of making an annual adjustment.

[robrien24 (Rick OBrien)]

@Ray_Livingston

ANY slave cylinder will work, provided you do not try to duplicate the (failed) self-adjusting feature of the “hydrostatic slave”, and use a string external return spring. You may, or may not, need to lengthen, or shorten, the pushrod, depending on which one you have. With the spring pressure plate, you need the thinner (in your case blue) throwout. DEFINITELY test that you can fully release the clutch BEFORE re-installing the engine in the car.

I’m still a bit concerned about the physical size of my AP/Borg & Beck HD3325 release bearing. It barely fits in the fork. In fact, I’ll have to dress down the parting line in the forging to get it to completely clear. The graphite area and ID are larger too. I have a suspicion this was intended for the V-12. Can anyone verify it’s OK for my application?

Thanks
Rick

[Wiggles (Paul Wigton)]

Looking back, I never understood the "hydrostatic " cylinder, given it allowed unnecessary contact between the throwout bearing and the pressure plate.

I completely concur with you, that a periodic adjustment is a far superior design, with this type of throwout bearing.

[Dagenham (Ben E)]

I’ve mentioned this before, but MGA’s and MGB’s all have a ‘self-adjusting’ clutch, that works just like the one on an E-type.

Their carbon TO bearings regularly go 100k with “common sense” use.

Jaguar really seems to have screwed this one up, because the carbon TO bearing in my car is virtually worn out at 29k.