Hi, I seem to have a strange problem with my 2006 S-type twin turbo diesel brakes. I had to leave it standing for a couple of months, just started once a month and moved it back and forth a bit.

Now when I drive it the brake pedal, as soon as it is touched, drops and the brakes stay lightly on. As I drive the brake pedal comes (after about 50 yards or so) back up. If I have to brake harder the pedal drops down further and again after moving off it starts to come back up. I've been stopped a couple of times with people telling me my brake lights are permanently on. 

I took all the wheels off, then the calipers to check for sticking but could not fault them. Reversing is the same, maybe even a little worse, as they seem to stick more and I have to apply more throttle to get moving.

After driving for a few miles  they seem to get a little better with less swift dropping of the pedal. I'm scratching my head on this one, Brake booster or master cylinder seem quite expensive so I'd really like to know if either may be the cause before splashing out on replacements.

Discs and pad are in good order the car has done 47k.

Thanks Al

It appears, after talking to a jaguar specialist, that this can be cause by a sticking rod. I took the cover off under the steering wheel and sprayed liberal amounts of WD40.

This appears to have done the trick.! no change of servo or master cylinder.. I'm overjoyed..

It was stull a bit stiff but after doing about 200 miles its now back to normal.

HI Al,

That's a cracking result. You can afford to treat your car to some TLC now, only having spent 30p on a few squirts of WD40..😆