D2 S8. Brake master cylinder.

Bandycoot · #1 1st September 2013, 06:38 AM

Morning chaps.

Are the brake master cylinders rebuildable with new seals or is it a case of replacing the old one with an new one?

Thanks

Steve

Adrian E · #2 1st September 2013, 01:29 PM

I can't see anything much in Etka that looks like a rebuild kit - they're about £230

Etka page attached

Bandycoot · #3 2nd September 2013, 08:25 AM

Thanks Adrian. If they are anything like the master cylinder on my 90 the they are not rebuildable. Ho Hum.

Adrian E · #4 2nd September 2013, 08:50 AM

Is it physically leaking or a symptom you're experiencing? Not sure it's a common failure point on these.

Bandycoot · #5 5th September 2013, 06:23 AM

The problem I'm getting is long pedal travel with generally poor braking performance. The overall performance has deteriorated over a period of time and with EBC discs and Yellowstuff pads the braking is normally very strong . I've changed the fluid repeatedly, bled the system again and again, changed the discs, pads. I'm now looking at the master cylinder as I'm running out of options. I also have a servo issue, which has just come to light, but I think this is just the servo hose leaking or split.

Adrian E · #6 5th September 2013, 06:31 AM

I was going to suggest brake booster as a possible cause - more likely than the master cylinder if it's not physically leaking fluid. You would expect dodgy seals in the master cylinder to lead to loss of fluid somewhere in the system?

Goran · #7 5th September 2013, 06:38 AM

Before you shell out on a new master cylinder, check for flex first. Ask someone to look under the bonnet how much the master clylinder flexes when you press the brake pedal hard. In the States they found on some cars it gets looser and moves too much, so they invented a 'brake block' which wedges between the cross bar and the end of the master cylinder to stop the firewall flexing.

http://forums.quattroworld.com/a8/msgs/5802.phtml

https://forums.quattroworld.com/a8/msgs/10684.phtml

Zip · #8 5th September 2013, 10:09 AM

Quote:

Originally Posted by Goran

Before you shell out on a new master cylinder, check for flex first. Ask someone to look under the bonnet how much the master clylinder flexes when you press the brake pedal hard. In the States they found on some cars it gets looser and moves too much, so they invented a 'brake block' which wedges between the cross bar and the end of the master cylinder to stop the firewall flexing.

http://forums.quattroworld.com/a8/msgs/5802.phtml

https://forums.quattroworld.com/a8/msgs/10684.phtml

I bought one of these off the guy in the states. Nice little modification, and seems to firm up the pedal feel when making "swift" progress. Beautifully made as well, and a perfect fit.

Zip

Bandycoot · #9 7th September 2013, 04:52 PM

Sorted!. It turned out to be valve in the servo hose just after it comes out of the inlet manifold. I changed this and everything is fine. Pedal travel normal and brakes as sharp as they should be.

I checked for flexing a couple of months ago and things were OK in this department but getting one of those blocks could be a good investment.

Thanks guys.

Steve