Wow! I just got back from a 4-day camping trip and I find lots of interesting contributions to this thread. I love Mike F’s videos. I’m going to have to do that. For me the important observation is how much better the Isuzu bellows functions. I had thought about using it but decided to go for the “original” look. Now I think, FWIW, it is an improvement and who but me will ever look under my car. I’ll make the change to the Isuzu bellows.
I’ll make a couple of other comments: First, my setup is with the short slave cylinder; hence my car does not use a hydrostatic setup. At the beginning of the thread I stated I switched out the springs. I.e., I used the “Jag” spring along with the Isuzu piston. I looked at that Isuzu spring and thought it way too “different” (stronger) than what appeared to be a factory-type spring, so I swapped the springs. I just flipped it end-for-end and it fitted onto the Isuzu piston. Re. the springs, hear, and actually believe, the comments on the uselessness of the internal spring. However, I cannot understand why Jaguar/Lockheed used an internal spring in the first place. Not truly knowing its function, I went with an internal spring…but a weak one like the original setup. I have convinced myself there is no harm in using it. I do think the stronger Isuzu internal spring is a game changer, so I chose to not use it…whatever it does. The external spring easily overcomes any counterforce attributed by the internal spring as many have commented.
I found it interesting that the pin fixing the pushrod to the T.O. lever has a land for the spring. That is not the same as the earlier cars. Also in my earlier car, there is no need to rotate the tab that the spring attaches to. In my case the spring is of such a length that it has plenty of “spring” in it when attaching it to the pin; at rest the slave cylinder will bottom out and I’ll just need to adjust the pushrod length so as to keep the T.O.B. off the pressure plate (that 1/16" adjustment).
I’m sorry I had to blow off some steam on this, it was a long weekend. Multiple times in and out with the clutch slave can do that. The efficacy of the lip seal may be better than the original cup seal. It really doesn’t matter. The cup seals work for many years in normal service. And if the cup seal in the clutch slave seems heinous, replacing it does nothing about the cup seals in the clutch master, brake master or the brake servo. So as a mod, it’s just an alternative way of doing it, not a sea change in function or reliability. It won’t regrow hair or make you fall in love again. The Isuzu part is dirt cheap, thanks to the donor cars disappearing from the road , so that’s a plus. And the best part of the mod may be the tight fitting accordion dust seal. As long as you spend your weekend driving, rather than staring up from the garage floor, you’ve made the right choice.
The questions surrounding the clutch slave seem to originate in Jaguar’s own confusion about how it should work, witnessed by a series of part number changes to the release bearings, slave cylinders, springs and adjustment procedures. I would guess that the design of this part was relegated to a junior engineer, or maybe to the Lockheed salesman. They weren’t paying attention, and it shows. The worst thing they did was to introduce the phrase “hydrostatic cylinder” to the discussion, and that naturally led to the “non-hydrostatic” slave cylinder which followed. Think about any hydraulic system you’ve ever encountered…clutch, brake, power steering, city water, rudder and aileron, whatever. Anything that works with fluid pressure. All are hydrostatic, because the system will be in motion until the pressures on the working fluid are in equilibrium. And so the non-hydrostatic cylinder is just as hydrostatic as the hydrostatic cylinder. I’ve finally encountered an automotive term that’s less accurate and more annoying than “spade terminal.” So let’s not fight about it, just blame Jaguar.
The clearer way to think about these systems is the way that they were described in the Lockheed literature: self adjusting vs manual adjusting. Pay attention to primary objective: the slave cylinder has to be set up to minimize wear on the fragile carbon release bearing. Which means that the resting position of the piston and the length of the actuator rod have to set up so that, in the case of the self-adjusting system, the release bearing just barely contacts the clutch plate. In the case of the manual adjusting system, there has to be enough free play to allow a small gap between the release bearing and the plate when the system is at rest.
Adjusting the mechanism correctly doesn’t require heavy springs or cocking the spring bracket to increase force. Nor does it always require forcing the piston to the end of the cylinder. It just requires careful attention to the position of the release bearing. This isn’t clearly conveyed by the set up instructions in the FSM. Worse, the set up instructions in the FSM applied to the release bearing/clutch slave hardware of the moment, which may not be what’s actually in the car 60 years on. They may not even have applied to what was in the car when it rolled off the line. You’re better off using the instruction in the Lockheed manual, even though they aren’t specific to any make or model.
Last word. Pay attention to the release bearing, not the discussions about seals, crushing the piston to the rear, or “non-hydrostatics.” The Isuzu mod is good, but if you go that way, just omit the spring. Otherwise, you will have to whittle down the actuator rod, and you may have the slave in and out of the car a few times.
Yep to all Mike. Except that last statement on the actuator rod. Granted I do not have brake fluid in my system as yet, but I don’t think that matters and I don’t believe I’ll have to shorten my push rod. As it sits now, the piston is bottomed out in the cylinder by the external spring. There is ample adjustment on my pushrod to eliminate the free motion of the T.O. lever. So I believe the push rod length is correct as is. I’ll just have to adjust it when there is fluid in the system.
I have to build the pipes to the master cylinder before I’ll know for sure.
Yes, but you used the weaker Lockheed spring, so that would seem to be another workable alternative.
The exercise isn’t to eliminate the free motion of the TO lever. With the clutch at rest and the external spring detached, you should be able to pull the lever arm at least 1/16" further back. It’s only when you apply the external spring that the free play should be taken out. I would submit that you would have a difficult time determining free plat with the stronger Isuzu spring and stock 4.5" rod. And remember that adding retracting force by cocking the external spring translates to more foot pressure.
As far at the 1/16" measurement, not only am I not convinced it’s critically precise, I’m not even convinced that the lever ratio is 1:1 or that the action is precisely proportional after 60 years of wear. A little looser is better than a little tighter. You should already have about 1" of free play at the pedal, whether the slave is adding 1/16" or 1/8" shouldn’t be palpable. But a dragging release bearing will cost you a tidy sum and/or a lot of work at some point.
IMO, there was no confusion. They knew exactly what they were doing.
I believe they knew exactly what they were doing. They called it hydrostatic for a very clear reason. This system was no longer mechanically adjusted by a mechanic, it was automatically adjusted. And it was not automatically adjusted by a mechanical means, it was automatically adjusted hydraulically. So they could have called it the automatically hydraulically adjusting clutch system. Or they just called it the hydrostatic system to differentiate from the mechanically adjusted system. The engineers already knew they were both hydraulic. However, you do not need to like the name.
Now this I am less familiar with, as I never worked on these cars in mass. (Maybe some who worked on these back in the day have more comments.) We all love to criticize this “stupid” carbon TOB. But look at it and compare it to the ball bearing TOB of the time. The carbon had no moving parts. Nothing to lube. Nothing to go dry. Since nothing can be perfect, it did not matter if it was slightly off center of the pressure plate… The fork mechanism could be simpler. Then look at the ball/roller bearing. It needed lubrication. Because of its location, usually lubed for life- not as common back then. And look at its usage. It would be at 0 rpms. Then, with the engine at 5000 rpms, one presses on the pedal and instantly the ball bearing would be accelerated to 5000 rpms. And at point of contact to the PP, the metal would be clashing/skidding. Maybe the carbon does not sound quite as bad?? And to life, what did a clutch typically last back then? 70K miles? Did the carbon TOB usually last that long/ What was the ball bearing TOB failure rate back then?
And to the hydrostatic style being so terrible. Was the problem the design? Jaguar was trying to eliminate a maintenance point, one that was probably already causing failure because it was not always done. I am sure Jaguar did fairly extensive testing before they released it. But just as we, 50 years later, are mixing and matching cylinders, springs and adjustment procedures, they were probably doing the same back then. Some were probably seeing this “new” style and installing a “missing” spring. Some were probably “correcting” the faulty adjustment and going for 1/6 inch. I wonder how many properly adjusted hydrostatic system prematurely failed?
As to the manually adjusted/non-hydrostatic free play spec of 1/16 inch. I believe the only “magic” to it is a determination of how often it needs to be service. If one desires to check and adjust every week, set the spec at 0.001 inch. If one wants to adjust it every 50K miles, adjust to half inch. But if one wants to adjust at a reasonable interval and still have quick pedal response, 1/16 inch was a good compromise.
Having said my say , am am not a big fan of the carbon TOB or the hydrostatic system either, but I believe we should look at these systems objectively. But to each their own!
Edit- BTW, Michael, although I used your quotes in my response, this is not to be critical of you. I very much respect your views- this was just an opportunity to express mine on this particular topic.
Tom
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.
Although I said the release bearing was fragile, that wasn’t a criticism, but rather recognition that it requires special care. 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. The discussions here and on other lists revolve around pedantic positions based on nothing but guesswork, misinterpretations of the FSM, part numbers, and personal opinion. Stronger springs, weaker springs, no springs, the spring doesn’t matter, the piston must be all the way to the rear, hydrostatic this, non-hydrostatic that. And don’t forget the lip seal vs cup seal debate. It’s all just hand waving. The self adjusting system was a fail…Jaguar themselves replaced it…because the bearing ALWAYS drags on the disc face. And despite what the FSM says, calling it “hydrostatic” has led generations of mechanics into mistakenly believing that it was hydraulically adjusted.
You say we should look at these systems objectively. And objectively, I lay under my car for three days experimenting with seals, springs, rods, pistons and adjustments. My objective observation is that physics still works. If the idea is to minimize wear on the hard-to-replace bearing, then the only way to get there is by having a little free play at the arm. How you accomplish that doesn’t matter, although I would say that if you think you have to begin by crushing the piston all the way back, you’re off to a bad start. If the secondary objective is not to burden an already heavy-footed system, then you also want to set it up with the least amount of spring tension. So a little bit of free play, and a little bit of spring tension to pull the arm back, and the rest is just talk. Although I would say that if my car had the self-adjusting slave, I’d add a spring to save the release bearing.
As for what amount of free play is right, if you view my video above and turn up the sound, you’ll hear a little squeak each time the clutch engages. That’s caused by wear on the rod end. Yes, I have to go in yet again to replace it. If there’s wear on the rod end, there’s likely wear on the pivot points on the release arm. Since these are buried in the bell housing, they won’t be serviced or inspected anytime soon. So how much free play do I need to account for sloppy pivot points, as well as to supply the proper gap? 1/16" won’t be enough. Lockheed designed the system, not Jaguar. And they say the free play should be measured at the bearing, not the slave rod. The measurement at the rod includes all the slop that’s developed over the last half century of use. There’s free play at both ends of the system, so the safe bet may be to put more free play in the slave, and take it up at the pedal if it feels loose. The point is that you have to think about the work in front of you, and accomplish what needs to be accomplished, without the fear of insulting the jaguar gods.
Is that really true? My understanding has always been that the thicker carbon bearing was introduced in '65 with the diaphragm pressure plate, which is “thinner” (distance from flywheel friction surface to contact face with throw-out bearing) than the older spring pressure plate. The “hydrostatic” slave did not come until, IIRC, early S2.
I’m not sure, but I just found this in the factory workshop manual, saying that they implemented at 7E4607, and went away from the self-adjusting slave on engine number 7E18356.
So, if I’m interpreting the information correctly, the self-adjusting design spanned 7E4606 to 7E18356.
I don’t know if there were any ‘jumps’ in the engine serial numbers, but if not, then that’s a lot more cars than the “short period” that gets tossed around.
Looks like the 7E engines were all S1 and S1.5, all 4.2s. Presumably the first was near 7E0000, so the first with Hydrostatic would be ~4600 in, then ended less than 14,000 cars later. That certainly puts the introduction early in the 4.2 run, but nowhere near the beginning. Wasn’t the diaphragm clutch there from the start of 4.2 production? And, surely, the thicker throw-out is needed throughout all 4.2 production?
~17,000 is correct for the entire run of S1 4.2s, and S1.5. That would mean the change to hydrostatic likely did not come in until probably 1966, and went away with the S2, more or less.
