Fred the Zed wrote:johny brando wrote:scott wrote:Kev there are two tiny holes in the master cylinder, make sure these are clear, think one is called a relief hole. A very fine piece of wire should open up the hole, which is probably full of shite......had the same problem on my A2.
Scotts correct ! Theres 2 tiny holes . 1 down stream of the the Piston seal this one acts when the levers is released after being pressurized .... this to allow released pressure to escape back into the reservoir the other tiny hole is upstream of the Piston seal & this one keeps the Piston chamber primed & it is this one that is likely blocked & trying to clear this using back pressuring via Caliper Bleed nipples etc will not clear the blockage, as back pressure cannot (by design) access this area , you will have to remove the piston & seal & then clear the tiny drilling using compressed air is best ...wire of any description can & likely will do damage. While your in there at the same time it's probably wise to put a rebuild kit through it & when bleeding the system take off & invert the Reservoir to start the procedure & this will ensure the reservoir is fully primed. Good luck & Cheers, Johny Brando.
I've has the rear master cylinder apart today as bleeding it is difficult and I wanted to make sure it was clean. One question..... what the 22mm nut for on the side of the unit? It was locked solid and I didn't want to force it.
Fred
Righto
The 22mm nut allows access to the 2 holes that Scott usefully mentioned. I haven't got access to an airline so I carefully used a fine bristle from a paint brush to clear out the tiny hole which had a minute amount of crud in it. A bristle won't increase the hole size like a wire will.
Once reassembled and fitted with a new HEL stainless line it bled quite easily, even though I've fitted an underslung AP caliper. Bleeding took about 20 mins, far quicker than I've ever managed it before.
Fred
