Rear brake mk 3

I have completed a rear brake m/cyl rebuild (thanks for the help L.A.B) and have previously done a rebuild of the rear caliper. One thing remains the same........ I need to pump twice to get a good bite on the disc. First pump after standing only a second or two will see the push rod bottoming on the m/cyl body.

Yes, I say "air in the system"as well but I have bled the system thoroughly and I don't believe there is any air present.

I recall when racing a TZ that there was a thing called pad knock-off due to discs not running true when hot and this seems similar, you need to give it a pump prior to actuation, but in this case the disc isn't turning.

Any thoughts would be appreciated.

Vince,

My guess is that you still have air in the systm. MK3 rear brakes can be tricky to bleed. Try "cracking" the tubing fitting near the caliper and purging the air out at that location.

Try wedging the pads to force the pistons right back into the caliper then bleed again. That usually works for me.

Cash

probably some air bubles hiding

I had the exact same issue a few weeks ago on my Mark 3. Had rebuilt the master cylinder and caliper and put on new pads, so everything should have been perfect.

Bled the lines thoroughly (or so i thought).

But I was getting the same problem you have. So i brought in an assistant to help with the bleeding (the eight year old kid next door - who felt very privileged to have such an important job). I had him tap and wiggle the flexible line repeatedly while i worked the brake pedal and wrench on the bleed nipple.

On several of his wiggle and tapping movements of the line - out came some more bubbles. I paid him a buck for his expert work and my brakes worked fine every since. Note- his services are very exclusive (soccer and surfing take up all his free time), but anybody who can provide a third hand will do).

Or you can tie a bungie cord on the brake pedal so you still have two hands free for the line jiggling and wrenching.

Good luck.

Part of the Mk3 flexible rear brake hose sits at a higher level than the caliper inlet; -and, as has been said already, air can get trapped in the hose, so I would suggest pulling the hose down and then tying it temporarily to either the swinging arm, or the exhaust bracket assembly before trying to bleed the system, as any air in the system will rise toward the caliper, and not tend to rise back to the high point of the hose if the hose was set in its normal position.

The first time I bled mine, I think I went through a pint of brake fluid. The tip on tying down the flexible hose sounds like the ticket.