Brake servo / booster replacement help please

A little advise please.

I've got a MY2008 (facelift) S3. The last few weeks its developed a hissing noise noise from the drivers footwell whenever I am NOT breaking. After a bit of an inspection and reading up I've worked out that the servo must be leaking. I've done a few tests on the servo and it seems to be operating correctly. However the noise is really doing my head in and although the servo seems to fine now I don't really want to risk it failing one day.

So I've decided to change the servo myself, I am a competent engineer and I'm not paying the huge price for a garage to do it. Has anyone done this before or know of a guide? Any specialist tools required? I appreciate that the engine needs to come forwards to get enough space. Will have to remove the engine from the gearbox? Or the drive shafts from the gearbox to get enough movement in the engine?

Any advice would be greatly appreciated.

Thanks.

Can't find any info on A3/S3 8P, however I've done some digging and found a bit if info for the Mk5 Golf GTI which should be pretty similar. Apparently you have to remove exhaust manifold and turbo and other hoses and bits and pieces then you can drop the engine down about 6 inches on a couple of jacks. Don't know if anyone can confirm if the same is true for the S3?

So I've bought the bits from Audi and I'm starting it this afternoon and hopefully will finish before the end of the weekend! I spoke to one of Audi's fitters when I bought the parts to get a bit of an insight. He says I'm brave for doing it on my drive. I took that to mean that he thinks I'm crazy! He advised me that the method of dropping it down on jacks should work. The only special tool required is to remove the clip that holds the pedal onto the servo. Audi won't sell me tool but he says I should be able to get it off with a couple of small screwdrivers. Wish me luck! I'll post the results.

Servo changed! Really wasn't a bad job. Don't get me wrong it's a big job, took about 9 hours to do but was fairly straight forward with no particularly awkward bits. Everything is easily accessible.

The way I choose to do it, which may not be the quickest or easiest but worked fine for me;
Remove engine cover,
Remove battery and tray,
Disconnect coolant hoses from radiator, bottle and heater matrix,
Disconnect intercooler pipes,
Disconnect A/C discharge from condenser and suction pipe from compressor (gas will need to be removed first),
Disconnect A/C high pressure switch wiring,
Disconnect oil level sensor wiring from sump,
Remove radiator fans and cowling (slides out of bottom in one go),
Disconnect fuel supply and return pipes from top of engine,
Disconnect servo hose join above gear box,
Disconnect anti roll bar drop links from front struts,
Remove drivers side lower dash trim,
Remove drivers foot rest,
Remove steering column to steering rack bolt (mark first so you get it back in the same place),
Remove lower wishbone connecting plate (large aluminium plate joining both wishbones) This should drop the whole steering rack and wishbone assembly,

Now you should be ready to lower the engine! I lowered the gearbox by 3-4 inches onto an axle stand then using a jack under the sump lower the engine by around 6-8 inches keeping on the exhaust, drive shafts and prop shaft,
Drain enough brake fluid out of the front brakes to empty the master cylinder,
Remove brake pedal from the servo (Audi have a special tool for this which they won't sell you) I used a screw driver to push the white lugs in through the pedal and pull the pedal away,
Disconnect brake lines from master cylinder,
Disconnect wiring from master cylinder,
Disconnect clutch feed pipe from master cylinder,
Remove master cylinder,
Disconnect servo hose,
Remove servo.

Reinstall in reverse.
Bleed brakes.

Parts required;
Servo (if you can't work this one out then probably best if you don't try this job yourself),
1 litre of brake fluid,
3 litres of coolant,
A/C compressor discharge pipe to condenser o-ring,
A/C compressor suction pipe o-ring,
I would also recommend changing the brake pedal to servo clip as it's easily broken and cheap,
A/C will require a pressure test and re-gas afterwards.


Hopefully this will help other people out before they take the plunge on this one as I found it hard to get any real info on this job before starting it.