I was wondering if anyone may be able to help me with a problem I have with my Octavia. Therre's a lot of history so please bear with me:

History:

• For the last 2-3,000 miles the car has been making a ‘wheel bearing’ type noise from the front wheels.
  
• It’s not the wheel bearings as both have been replaced. All bushes and struts are in good condition or have been replaced, as far a I know (and have been told by 2 garages) everything else in the wheel / hub are is OK.
  
• Front disk’s and pads were changed - same rotational noise but a different ‘tune’.
  
• Went for a service – change brake fluid – mechanic had a problem bleeding the system but got the job done with a bit of tenacity.
  
• Mechanic didn’t bleed master cylinder properly & break pedal was really soft – Durr!
  
• Car goes back in & system bled properly.
  
• Car drives fine for 3 miles then becomes apparent that brakes are binding & overheating. Get to 5 miles and the car becomes virtually un-drivable as the disk / pads heat up and expand.
  
• In hind-sight the binding problem may have been there before the brakes were bled properly – as they started to squeal a bit while driving after 5 miles (when I got home) – I suspect that the air in the system allowed the pads to retract as the disks expanded.
  

Any ideas as to the problem?, could it be a faulty master cylinder? – and if so what is there to go wrong in it and how do I test if it’s faulty?

It could be a faulty master cyl,depending on how your mechanic bleed your brakes he may of damaged the seals in the master cyl,it may be a faulty servo.if it was driving ok(no binding) before he bleed the brakes my guess is the master cyl.

The slides haven't got stuck have they?

My first car had the tin caps on the end of the bolts rust through and allowed water into the slides causing them to seize.

Or as other people say the master cylinder may have failed.

I wouldn't think that it's a problem in the caliper as it's all of the brakes that are causing issues and I'm sure that I'm not that unlucky to have all 4 seize at the same time! - the front one obviously get hotter as they're bearing most of the load.

What is in the master cylinder to go wrong (other than seals as you suggested)? - am I right in thinking that it's just a resevoir for the brake fluid?.

Is the binding likely to be related to the 'wheel bearing' noise that I've got - or is that likely to be another issue?

Cheers for the help so far.

From an Audi site:-

If you are planning to change the pads you'll need to retract/wind back

the calipers - you may need a special tool to do this. When you wind back

the calipers you will force fluid back out & up through the system - this

can i) damage your ABS and ii) invert the seals in the master cylinder also overflow the fluid reservoir. Solution is to release fluid from the bleed nipple on the caliper (via a hose into a jar!) as you wind the thing back.