Brake servo,booster

[Woodside Auto services]

My 2006 ,2.7 diesel S Type has a brake problem, simply put when you gently press the pedal it almost goes down on its own,could it just be a weak spring in the servo or is it possible to have too much vacuum on it from pump, also is it possible to fit a servo of an xf,as the part number on mine matches an xf,but doesn't appear to match any I've seen or enquired about ,ps the brake's work fine it hasn't got a soft pedal.thanks for any help

[JustBadly]

It wouldn't hurt to introduce some lubricant into the vacuum device since there are several springs in there. A spray oil (no silicone) for example, there has to have been a grease or otherwise used during assembly and by this time it will have dried out. Galling, or cold welding as it is sometimes referred to, is a form of severe adhesive wear between two metal surfaces.

[JOE-DOT-COM]

Hi

That sounds like the master cylinder

if you pump the brakes with the engine off, the pedal should come up a bit and go hard,

if it goes down slowly then its the seals in the master cylinder, a good master cylinder and servo, should stay high and quite hard, once the engine is started the pedal should drop slightly

the diesels had problems with the servo and master cylinder been contaminated with engine oil, theres a non return valve between the servo and engine on the vacuum line that sticks open and lets oil vapour into the servo under boost, eventually the oil destroys the servo and master cylinder.

but your sounds like it might just be the master cylinder, servo can be checked once the master cylinder is off, to see if the servo has oil inside it, it should be clean and dry inside.

this was a recall for landrovers with the same engine

cheers

Joe