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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Appreciate you posting this. I had a problem with mine last month and there was only one person on here who was a brake specialist that gave an accurate diagnosis. So along with hours of searches I came to the conclusion that not to many are familiar with the working of this unit.
The early 355s have the same unit.
Question, when you said the jaguar unit was the same except that it has a "mirror image". What did you mean by this?

 

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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Miroljub, I'm sure you have already investigated this, but are the Jag assemblies the same in both LHD and RHD models?

 

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.

 

Way cool! As if what you've found so far wasn't already encouraging, this is even more good news. Thanks so much for doing this research. About the only thing that dampens my enthusiasm for the 348 is the ever-looming prospect that something unobtanium will fail, and the brake master is kinda necessary. Finding a path to a replacement and/or rebuild parts would be huge for the community. I'm still shocked that it's not available as an off-the-$$$helf factory replacement part. Amazing how much $$ Maranello leaves on the table with regard to replacement parts.

I'm curious as to whether or not the pushrods will just interchange, so looking forward to your findings there.

 

Wow, this is great stuff!! How did you know about the Jag unit being so similar? Do you by chance know what the replacement cost is for the Jag unit? As I recall the Ferrari unit from Ricambi is over $12,000. Unbelievable...
One more question: do you know if the Jag model with this similar unit was available without ABS? It would be handy if in the future when things start going bonkers with these complex systems, if there was a simple non-ABS brake master cylinder alternative.
Great job doing this research!

 

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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Its great to see all this. One of the few things I haven't had apart. Yet. Thanks for posting.

 

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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Great thread

 

If your main goal is replacing seals, when I dig around on line it looks like there maybe a seal kit available for the Jaguar unit. There is a site called Jaguar Heritage, if you go into the XJS parts and into brakes and then to "actuation assembly and reservoir" they have a part JLM1477 they call an O ring and seal kit for £20. I wonder if that would do the trick.
For the same model listing they also show a non-ABS standard vacuum boosted master cylinder, but the bolt hole pattern that attaches it to the car is different from the pattern for the ABS unit. So aside from fitment issues of the vacuum booster, you can't just unbolt one and slip the other into it's place.
Does anyone know what people who race 348s do for brakes? Do they go with the stock ABS pump and actuator/master cylinder unit, or do they save a boat-load of weight by scrapping all that for a non ABS master cylinder?

 

May i ask why did you strip your ABS master cylinder?
As i said last month i had a problem with my pedal and the problem was in the abs valve block on the master cylinder. So i striped mine down to.
So what was your problem for you to want to undertake this job?

 

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!

 

And here I thought that you only liked to take things apart.

Very cool thread Miroljub and a huge benefit. Thanks!