348 Master Cylinder - ABS

I bought a used Jaguar master cylinder / ABS, ATE number 10.2123-0105.9, which is the same as the 348 MC (10.2123-0106.9) except that it is a mirror image. The reason I bought it is to get all the seals out (which I am almost sure will fit the 348 MC) and see whether they can be sourced separately.
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First, I separated the ABS block from the cylinder. Note the 4 small O-rings (rectangular). In 1998, Jaguar issued a bulletin informing that, if you encounter a problem with the ABS operation, you can now replace the 4 O-rings as they are available separately thus there is no need to replace the whole assembly. This was, however, 8 years after the first installation of this type of MC-ABS in Jag XJ Sedans and XJS, 1990-1994. The part number of the 4 tiny O-rings is JLM11336 and it is currently available on Ebay for only USD 263.
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Next, I separated the two sections of the MC. After I undid the two M10 bolts with torx heads (easy with an impact gun, holding the MC in my hand), I could separate the two halves with a bit of gentle knocking with a plastic hammer. There are two tiny O-rings on one half and a large O-ring, supported by a wavy washer, on the other half. Will go deeper tomorrow (if there is a way to get the pistons out).
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When in the installed position, the 348 assembly has its ABS Block attached to the right side of the MC, the Jag assembly has the ABS attached to the left side. The front part of the assembly (the one with the fork) controls the pressure from the pump to the MC, i.e. it is equivalent to the Vacuum Booster. These front parts appear to be the same (same orientation) on Jag and 348 except that the high pressure pipe connection (high pressure from the pump) is on top on the 348 (banjo just in front of the reservoir) and on the Jag's it is slightly below on the side. The blanked extension in the casting on the left side, just below the banjo, of the 348 unit is where the high pressure pipe is connected on the Jag unit.
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Excellent idea Mike, I didn't think of that. Just checked at Ebay UK - the RHD Jaguar MC-ABS is the same as the 348, the ABS block is at the right side of the MC (the problem is that Ebay is full of American sellers).

So, it appears that the RHD Jag MC-ABS can be used on the 348. The high pressure pipe which, on the 348, is screwed into the banjo on top, can just be screwed into the port on the side of the Jag MC casting, positioned slightly below where the banjo is on the 348. Another difference is the fork - considerably longer on the 348 MC. I have yet to disassemble this part of the MC (the actuator body) and see if the forks can be swapped. If not, I believe that the whole actuator bodies can be swapped. More pictures of the Jag MC disassembly are coming soon.

 

When a British friend of mine (classic car restorer, lives in Malaysia) saw the ABS pump in my 348 he told me that it is the same as what the XJ40 Jags and some Range Rovers have (he also said the system was s**t). Then I checked the Jag MC-ABS units on the net and saw the similarity. I could not find any new Jag units for sale anywhere but Eurospares have new 348 units at GBP 3,500.

I don't think the Jags had a similar Master Brake Cylinder but without ABS. Models earlier than XJ40 had a vacuum booster and a conventional MC. The friend I mentioned did a number of conversions on Jags from the ATE MC-ABS (like the 348's) to the vacuum booster MC. Easy on Jags as it was used on previous models and there is enough space; not so much space in the 348.

 

Continuing with the Jag MC disassembly - it was very easy, just pulled it apart. The lip seal next to the smaller spring is the one that does the braking in a 23.80 mm bore (applies pressure to the calipers).
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Already found a replacement for the 23.80 mm lip seal (the seal that actually does the braking) - one example is the MC kit for the Mercedes W123. This size (23.80 mm) is quite common in ATE master cylinders: BMW-s, Volvos, etc. so it shouldn't be a problem getting one from their rebuild kits. However, the problem will be finding that 37.40 mm lip seal shown on the pic in my previous post. The rest are O-rings and it's just a matter of finding them made of the right material for brake fluid (EPDM, Silicone, Aflas, Viton Extreme? etc.). To be continued...
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Final part for the MC - the pressure switch out (3 O-rings).
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Next, the Actuator Body. Control arms taken out, one O-ring under the screw-plug. The fork just unscrews.
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The Valve Body fully disassembled. The pushrod is attached to the piston on the left. It pivots and turns (ball & socket inside) but it cannot be pulled out. The pushrod is actually attached to the inner sliding rod (the one seen in the "window" of the big piston with a hole in it). The inner sliding rod is retained by a solid staked pin. If this pin is removed, the pushrod can be pulled out together with the sliding rod but I don't think it can then be separated as there appears to be a permanent ball & socket joint between the two.
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There are only two seals in the Valve Body - an O-ring supported by a thin teflon split shim at the fork side and a teflon ring inside the body.
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The small Control Arms, and their engagement into the big piston of the Valve Body, seem to be different between 348 and Jag. I can only compare the 348's control arms shown on the drawing in the workshop manual with the arms taken out from the Jag's unit.
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I hope that someone has an old 348 MC-ABS and will disassemble it so that we can compare the innards. There could be two possibilities for swapping the forks/pushrods:

1. Take out the Jag pusrod together with the inner sliding rod (after removing the solid pin) and insert the 348's sliding rod and pushrod, if the sliding rods are same.

2. Replace the whole Jag (big piston)-(inner sliding rod)-(pushtod) assembly, shown at the left side of the picture, with the assembly from the 348. This would most probably require swapping of the control arms (attached to the screw-plug) assembly as well.
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I have already checked this. JLM1477 is a Reservoir Seal Kit, 3 or 4 seals associated with the plastic reservoir only. The only other kit by jaguar for the MC-ABS is JLM11336 (JLM11337 for the XJS) which consists of 4 small O-rings (10mm OD, rectangular section) that go in-between the ABS block and the MC. These are sold at around USD 250. I found a couple of sellers offering this kit (one on Ebay) but none of them show the picture (so that you don't shout "what the...250 for these!"). You can, however, shout after you have bought them and see them. This is the $250 JLM11336, the ruler is in milimetres.
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The MC-ABS in my 348 is perfect, it is dated 1996 (my 348 is 1991 meaning it was replaced by the PO at some point, looks like quite recently). The reason why I disassembled the used Jaguar MC-ABS I bough is to see whether it is easy to do (very easy) and to get a set of spare seals for my 348 MC-ABS; for, I hope, very distant future. The Jag MC-ABS is dated 2003 and the seals look excellent so it is a good source. I bought it for about the price of the 4 tiny seals, Jaguar p/n JLM11336. Plus, I now also have a complete spare ABS block.

I nearly forgot - I also did it for the benefit of the forum members!