Urgent(ish) - changing a brake servo

[smoker]

Hi - further to a post a few weeks ago I'm convinced my brake servo is finished (hissing from the pedal area during and after brakes applied. Vaccum disappears in seconds of turning off engine).

MOT is now imminent, therefore lookign for real world guidance on how to change the offending article. Can it be down without breaking into hydraulic circuits?

Thx al

[rory_perrett]

The short answer is generally yes. Not done it on a Xsara but the usual form is that the master cylinder is bolted onto the servo (normally 2 nuts in studs). Once undone the master cylinder can be moved being careful not to damage the brake pipes. Disconnect the vacuum pipe from the servo and the servo rod is then disconnected from the brake pedal and the servo unbolted from the bulk head. If you are lucky there is enough play in the brake pipes to move the master cylinder sufficiently out of the way to get the servo out.

Repair time for a servo change is 1.5 hours. Are you sure it's the servo and not a failed non return valve or split hose?

[smoker]

Many thanks for the quick reply - sounds like it might be doable at home. I can't be sure it is the servo. However, the hissing noise is definately in the footwell and all I can see is the end of the servo poking through the bulkhead with the rod attached to the brake pedal. I hadn't fully appreciated that there is a separate non-return valve (assumed this was built into servo) - I guess that could be a contender depending on where it is. Don't think it could be a hose as I guess those are all under the bonnet (i.e. vacuum pump to servo) and I probably wouldn't hear them leaking from the driver's seat.

[citronut]

you may be correct on the servo leaking,
but the test for the servo working or not at the MOT is,

with the engine off pump the pedal to dissipate any vacuum in the system, then on the last press down hold your foot pressure on the pedal whilst starting the engine, if the pedal sinks it will pass the MOT

the valve is usually pluged into the engine bay side of the servo body, and has the vacuum pipe attached to it

[smoker]

Well what a £$%^&* nightmare. Hint - if you've got a diesel xsara and the servo fails, your first call should be to the local scrap dealer to see how much they'll give you for the car. The way I got it in and out is get undertray off, remove o/s top engine mount and drop engine, remove sundry vacuum hoses etc then prize apart the old servo and remove in bits. I then squeezed in the new one zip-tied together to reduce its overall length and once roughly in place, cut zip ties. THEN, realise that the servo you've been sold doesn't fit...

Car now completely immobilised while I see if I can get the right part next week.

I know this may not go down well here, but I really am shocked how badly designed and built the car is.

[addo]

I think it's one of those situations where you're suffering the consequences of forcing a left-hooker to be built as RHD.