Loss of braking on Series II car.

[skodajag]

My braking reduced significantly although it remained progressive and with no pulling to either side. Pumping brakes hard a couple of times, I heard/felt something give and full braking was restored. Waited for it to go again which it did and suspected loss of breaking or front or rear system. Tested it on gravel which showed that it is loss to the rear wheels. Fluid levels all correct. Advice appreciated on what I should check first....

[David Oslo]

You need to pull master cylinder and overhaul it. Or replace it with a new unit if you prefer. Costs are ?20-ish versus ?180-ish quid for OEM parts.

One of seals on the intermediate piston within the master cylinder has failed. Hence loss of one circuit. However the design is fail-safe so the piston bottoms out (hence the soft pedal / loss of brakes feeling) and then continues to work for the remaining circuit (hence the gravel results).

You've done all the checking you need to do. It's just to order parts now. Or book into garage, whatever your preference.

[skodajag]

Thanks David. I discounted the master cylinder, because I fitted a new one about 300 miles back. But I suppose, with the quality of replacement parts, that was unwise....

[David Oslo]

Have just read a post from Heuer (on clutch slaves) noting that he has changed two clutch slaves due to failed seals (and is now on AP NOS part).

I was going blindly from your symptoms. I guess adding in a "new" master cylinder with seals potentially of the same quality as Heuer and others experience makes it even more 'plausible'.

Golly... I am looking forward to the coming season now ... I am busy fitting "new" clutch slave & master cylinders right now. Maybe I should just pop the old BW auto 'box back in the car :D