S3 V12 Brakes Sticking on... a few seconds then releasing

[NigelHCooper]

This is getting progressively worse. Hit the brakes, wonderful stopping power with new Green Stuff and the brakes stay on, gradually releasing in a few seconds or after driving a 100yds or so, (A tad embarrassing at lights and roundabouts)
1, Someone suggested the hose flex to the IRS
2, I thought stick calliper piston or
3, Dodgy brake servo hanging on too long
before I dive in, any clues or suggestions on diagnosis of which this may be, or another issue?
Thanks, Nigel

[PoB]

There are to my knowledge about 3 reasons for this:

1 Air valve piston sticking, remove the white plastic air valve and there is a small pin sticking out. This sometimes sticks causing brakes to bind.

2. Failed IRS or caliper hose

3. Collapsed servo hose

If you still have original hoses hydraulic and servo then replace, they are 35+ years old

Regards
Pat

[NigelHCooper]

There are to my knowledge about 3 reasons for this:

1 Air valve piston sticking, remove the white plastic air valve and there is a small pin sticking out. This sometimes sticks causing brakes to bind.

2. Failed IRS or caliper hose

3. Collapsed servo hose

If you still have original hoses hydraulic and servo then replace, they are 35+ years old

Regards
Pat

Thanks Pat I will get on it, whilst the vacuum pipes on the engine are all new, the others are original.
Regards Nigel

[body159]

Hi,
I inherited my fathers S3 e and it had a similar problem but the brakes only held for one or two seconds. It turned out to be the use of synthetic brake fluid causing the seals to harden. The problem was cured by replacing the fluid with normal hydraulic type.

[DaveK]

I inherited my fathers S3 e and it had a similar problem but the brakes only held for one or two seconds. It turned out to be the use of synthetic brake fluid causing the seals to harden. The problem was cured by replacing the fluid with normal hydraulic type.


There are many myths surrounding synthetic brake fluid it wouldn't be that your fathers E had never had the seals changed from new would it? I have run with silicon fluid from day one on my E-Type (5 years now) and have never had a problem and to be honst wouldn' use anything else.
Wouldn't like to risk the paintwork.

Dave