Can someone explain the advantage or disadvantage to the 1994 mid-year ABS Brake System change? I've been reading about the ABS problems and how it causes complete brake failure. Did the mid-year change at VIN 198334 make any difference in the failure rate?

Thanks,
BQ

 

BQ,

The revised system from what Jaguar in the UK call the 1995.25 Model Year at VIN 198335, is a fundamentally easier system. It uses a traditional simple reservoir-fed master cylinder on the front of a traditional servo unit and this passes fluid to an abs modulator unit.

The earlier system uses a system where the pedal acts directly on an reservoir-fed actuator unit (This is not the master cylinder!) The "master cylinder" is merely the last chamber of actuator unit. The unit has the ABS valve assembly directly attached to it. This is why the whole unit costs £1000.

I wouldn't say the earlier unit is inherently more troublesome, it's just that the use of this major actuator unit & ABS valve block is expensive which necessitates more complex home repairs when problems arise. Whereas the separate master cylinder of the later system is about £100 and the abs modulator unit is a Ford part that was also used in certain Ford Granadas.

Apart from that, the rear discs changed to ventilated rather than solid.

Hope that helps.

Paul

 

That is Interesting!

Would it be possible to easily remove the Combined Actuator/Master Cylinder System from an 89/90 XJS and replace it with the later System as used on a 1995 XJS.

Any idea how much the Parts would cost as well as degree of difficulty in doing the Conversion.

Does anyone have any photos of the later System on the 1995 to make a comparison?

 

Thanks Paul for your explanation. Now I understand. A wise person recently suggested removing the ABS and replacing it with the parts from the entire non-ABS system from the calipers backward. I've never really thought much of ABS brakes anyway. I sounds like all you need is an early donor car. With all the non-running early 80's ones I see on Craig's List cheap, it looks workable.

BQ

 

Supplementary question : can the later model vented rear discs be fitted to outboard located rear discs on 1993 6.0 with early Teves abs or do they require different calipers ?

 

Paul,

You need to fit replacement calipers to fit the vented discs.

Paul

 

Thanks for your reply.


Any opinion as to how worthwhile this could be

 

Paul,

My suggestion: Don't bother at all.

The XJS is not an under-braked car in any form. The load on the rear brakes is much, much less than the front. I recently changed my rear outboard solid brake discs & shoes after 40,000 miles! I really can't see the need to change from the outboard rear solid discs to the vented type. Just my humble opinion.

Paul

 

Thanks Paul, your opinion and the reasoning it's based on seems sound to me