Hey guys,

with my brake system in pieces, I was wondering: do the master brake cylinders on these cars fail? Especially the ABS system ones!?

And then the question: are the cylinders serviceable? My 960 had one you could take apart without any special tools... And then of course service...

Cheers guys!

Damien

PS: no need to mention the ABS block, that is totally healthy and fine

 

Daim,

I'm sure it may have happened, but I've never heard of seals failing on the Actuation unit (I'm assume that's what you mean?) on the Teves ABS cars. I've never been able to track down a source of the seals so maybe it's just as well that they don't seem to fail!

LookingLooking forward to seeing pics of your stripped-down valve block!

Paul

 

Look in my thread, you'll see them there

And I was actjally as written refering to the main brake cykinder. That what the brake pedal is attatched to

 

Daim,

I'll go and have a look the pics!

The overall unit that is connected to the brake pedal on the Teves system is referred by Jaguar as an Actuation Unit. The "master cylinder" is a small chamber at the very front end of that Actuation Unit, which is providing the fluid pressure to the front brakes . It has discrete seals which used to be sold as part of the total seal pack for the Actuation Unit by Jaguar, but they haven't been available for at least 13 years. I'm sure that Jaguar must have the detailed spec for all those seals documented somewhere. I might try and talk to them sometime and see if I can get the spec.

I'm not sure why the seals never seem to fail. Maybe because the Actuation unit is quite unusual or perhaps because other parts of the system seem to fail first!

Cheers

Paul

 

Cheers Paul.

I have heard of the 'actuation' unit fail ing on normal servo assisted models (non ABS) and they are still available new. I was wondering if I could take it apart. I believe the unit is 'standard' ATE metric part (all screws and nuts I have found were metric). So I would assume it shares parts with other cars... Especially since the adapters (between body and actuator) are custom drilled (IIRC the bracket to mount the actuator to the body has different part numbers as ABS vs. non-ABS).

I would therefore assume it is a standard but altered ATE part...

But as the previous owners had the fluid changed very commonly, I would expect the master cylinder aka actuator to be in a nearly new condition...

 

Yeah, they go out. Mine did around the same time that the seals went out on my rear calipers. Very serviceable (88 non-ABS). Took probably 2 hours including painting the master and bleeding.

 

Hi Daim,

I've never taken apart an Actuation Unit. However, it is really quite different to a Master Cylinder as used on the pre-ABS cars which is simply a single chamber running a tandem piston arrangement to two ports. My knowledge of the Actuation Unit is from the various diagrams in the workshop manuals. As you probably know, it works quite differently using a lever mechanism to initiate fluid flow via pumped assistance for the rear brakes and return of fluid to the reservoir. The secondary mechanism allows a separate small piston pressure into that very front "master cylinder chamber which provides front non-boosted fluid to the front brakes and also allows the initiation of the secondary boost assistance to the front brakes.

So although it's very different from a simple Master Cylinder, I suspect it could be broadly the same type of Actuation unit as fitted to many GM cars that used the Teves II system. The pump and accumulator seem to have been used on some GM models, so perhaps the same type of Actuation Unit was used?

Jaguar used to sell a service kit but that's been NLA for many, many years. Knowing how many US cars are sod, I'd be surprised if there isn't some source of a service kit for GM models that might be suitable if they really did use a similar Actuation Unit. I wonder if they are relatively reliable compared to a Master Cylinder because most of the functionality and pressure control is achieved by the pump, accumulator and valve block rather than the seals of the chambers in the Actuation Unit?

It would be really helpful if we could gather some detailed knowledge on these units as it's the one relatively unknown part of the system. I'd hate to suggest that you pull yours apart but if you did, I'd really love to see some pics!

Cheers

Paul

 

I won't be pulling my 'actuator' apart, as I don't want to have to buy another one. I'll be getting a used one with unknown function (something I scrapped with my scrap XJ-S DOH!!!!!) and taking that to pieces just to see how it looks inside, what is there and what can be repaired/replaced.

The MK II setup seems a quite popular fit. Quite a few Fords had it. Like the Ford Granada/Scorpio (depending on country etc.), the Saab 900 and afaik the 9000 (as they were independant), and a few British makers, like, IIRC, Rolls Royce and Bentley, until they split.

 

GM also used the M2 in some cars, Reatta was one I know of.

You do raise a good point here Daim, and it would be interesting to compare a unit from GM or Ford to see which parts are interchangeable.

 

Have you got a copy of this

 

Cheers Warren, but I have that in my super duper Jaguar book... All included as supplements...

Googling more pictures came up with Saab 9000 and 900 using the same initial base unit BUT with a few little differences. The pressure chamber was part of the main unit...

The Lincoln MK VII has the MK II too... But again, a little different. But maybe adaptable...

 

Yep the XJ40 Mk2 system also had the pump and accumulator as part of the master cylinder.

 

Hi Warren,

I thought the XJ40 used the same setup as the Mk 2 Teves XJS system with a separate pump and accumulator on the other side of the car? I've stripped an XJ40 to get parts for a colleague's XJS and it was fundamentally the same braking system as my XJS. Perhaps overseas cars were different?

Paul

 

They did change with time. I think the XJ40 had the same setup until around the minor facekift, when the XJ81 (V12) was fitted. Space was a problem and they changed a few bits. The X300 got a complete Bosch kit. The X308 again a totally different one...

 

Who knows what Jaguar did, all of the XJ40's I have seen, and that is not a lot have had the integrated system, the PDF I attached also mentions the XJS has a separate pump unit and the sedan an integrated system.

I know - Jaguar used up all of the old XJS systems on some XJ40's. I'm only half joking here.