Braking Issues XJ40

My 1990 XJ40 (4litre straight 6) failed MOT - rear brakes inoperative on rear n/s and only 25% on rear o/s

It is presently with The Jagman in Wigan and he tells me he cannot bleed rears because master cylinder appears to be causing fault, he has never expererienced failed master cylinder in all years he has worked on these cars. Although car is over 30 years old it has only done 45k miles.

Couple of questions-

Anyone expererienced similar problem and any advice on fix?

I may be able to get one through David Manners (used unit) I am told they are tricky cos one may be working on one car and not work when fitted to mine…odd

Any help would be welcome.


You are on the wrong list, Dave - we deal with earlier, ‘series’ cars…

…which have master cylinders that fail often enough to be familiar for any mechanic - ‘these cars’ he refers to must be unique in that respect…?

xj6 85 Sov Europe (UK/NZ)

Hi Dave I’ve moved the query onto the correct list.
It sounds as though the mechanic is conversant with the XJ40.
The fact that there is an imbalance between the rears is obviously a concern, I take it he has already reconned the calipers to ensure they are working as they should?

Hi Dave, that’s a very unusually fault. The only thing I can think of that would cause those symptoms would be two siezed or partially siezed calipers. You mentioned in a previous post that you don’t use the car very often and this can cause the calipers to freeze. If the calipers are not sliding freely on the guide pins the pistons won’t depress so little or no fluid can come out of the bleed nipples. However when I took my car to Jagman he was very knowledgeable regarding XJ 40’s so I’d be surprised if he hadn’t checked for siezed guide pins ? As he has already pointed out the master cylinders are usually very long lived.


I can only suggest you use the search function (magnifying glass icon upper right of this page) in the XJ40 archives for “rear brake bleeding XJ40” to find loads of posts on the subject, some of which also question the possibility of a (most unlikely) master cylinder failure.

Remember you DO NEED the Teves accumulator on your car to be pressurised to effectively bleed the rear brakes.