HELP - NO BRAKES!

[brm brm]

Happily bimbling back from Castle Coombe yesterday after a quick blast through the back roads to Tormarten and all is well, 10 miles further down the M4 and I decide to brake gently when....... OOPS no brakes, pedal goes to the floor and no pressure. Frantic pumping and I get some brake pressure back but for the rest of the (slow) journey home the pedal is on the floor at the slightest touch. On investigation no leaks and fluid level OK, bled the system completely and went for a test drive, OK for about 20 min but again after 10min on the M4 with no real use the pedal is back on the floor and no brakes. I am very baffled so would be grateful for any pearls of wisdom... master cylinder perhaps???? Russ (and SEAC)

[GreenV8S]

Possibly pad knock-back from a duff wheel bearing? Peter Humphries (and a green V8S)

quote:Happily bimbling back from Castle Coombe yesterday after a quick blast through the back roads to Tormarten and all is well, 10 miles further down the M4 and I decide to brake gently when....... OOPS no brakes, pedal goes to the floor and no pressure. Frantic pumping and I get some brake pressure back but for the rest of the (slow) journey home the pedal is on the floor at the slightest touch. On investigation no leaks and fluid level OK, bled the system completely and went for a test drive, OK for about 20 min but again after 10min on the M4 with no real use the pedal is back on the floor and no brakes. I am very baffled so would be grateful for any pearls of wisdom... master cylinder perhaps???? Russ (and SEAC)

[tuscanboy]

Another likely reason is that after heavy use at castle coombe the brake fluid has boiled and now has water in the system. Although this effect is reversable, it never really goes away and will re-appear much quicker on susequent occassions. Only solution is a fuid replacement with some higher quality fluid. Steve Edited by tuscanboy on Monday 25th June 14:09 Edited by tuscanboy on Monday 25th June 14:10

[mikeb]

Could it also be that your car was sulking after we was robbed by the Lister!!??.... On a serious note, I would change your fluid asap. Mica Blue 350i

[alisonh]

Russ, I think I passed you on the M4 (blue S3), also on the way back from Castle Combe and did wonder why you were tailgating a rather large HGV. Thought you must have a problem, as I couldn’t see much enjoyment from sitting on the backside of a lorry on such a pleasant evening. Sorry, not much help but we all slowed to your pace a bit further on.

[Brm Brm]

HMMM sulking because Lister managed to pre-book a safety car could be the answer and yes, it woulod have been me loking rather glum in the inside lane - not a natural habitat for a SEAC! Seriously though, if anyone is interested I spoke to Richard at Wedge Auto this morning and these symptoms are well known to him. The fault is apparently an internal seal in the Master cylinder that fails, initially when the fluid is hot, but obviously getting worse with time. The only other possibilities were the fluid or a wheel bearing (see above)but as I said originally, the first thing I did was a full bleed and the bearings checked out OK. Good news is that Richard has master cylinders in stock, and they are not too expensive.(interestingly the best the Factory could come up with was a "part number to try"!) Guess what I'm doing on Staurday afternoon!!