hello
I have a beautifull xjs 85 coupe that im using as daily driver here in NYC. Last week, going to the beach on a very hot day the brakes fail out of the blue on the middle of the Rockaway bridge...pedal almost all the way down with a hisssing sound like loosing air when pressing the pedaI. I stopped the car terrified I turned off and I wait. when i turned on again the problem was gone. I drove it for some days more without a problem and suddenly again in very similar conditions. I brought it to the mechanic and is telling me the master cylinder haa a leak and not much brake liquid was left on the system. Im not a mechanic but my filling is that if this is the cause of the failure the behavior of the brakes should be consisting and not failing once in a blue moon without previous sign. The AC stopped to blow cold close before the first brake incident...I dont know why I thought this could be related.
I would appreciate any suggestion on the matter

 

when its happened to me after a couple of years of not using it, it was a sticking caliper piston on the rear brakes although it could be any of the pistons, boiling the brake fluid,

 

And....you'd be wrong

Master cylinder failures can often be inconsistent. It's plausible that yours is faulty.

Hopefully, though, the mechanic thoroughly inspected the entire system and didn't merely assume it was the master cylinder at fault, or assume that *only* the master cylinder could be at fault.

Cheers
DD

 

Hi Volido

It sounds like it could be the Diaphragm in your Brake Booster/Servo

Have a look at this Thread:

https://www.jaguarforums.com/forum/x...ooster-147666/