Hello, new here but really struggling to find anything concrete to answer my question.

I have just replaced all rear calipers, pads and discs on my mk2 Octavia. At first I used the pump and hold method, at one point the pedal was lifted a small amount while the bleed screw was open. I now can not get a decent pedal. The pedal slowly sinks down, but does not touch the floor, though it is fairly close to touching the floor.

Worries the master cylinder is shot, didn’t know the pumping of the brake pedal can damage it.

I’ve bled every wheel, multiple times on the rears.

Car brakes well enough, but I’m not too confident in its ability.

What could I do to rule out the master cylinder? If it was the cylinder at fault, would the pedal actually touch the floor?

Thanks for any help

you did put the correct side callipers on ? if you put the d/s on the p/s the bleed screw is at the bottom and it will never bleed

I did yeah, both side nipple is pointing up

Does the handbrake now have a longer travel? If so you may have not set the correct cable clearance at the calipers and this can show up as a longer initial footbrake travel. However this will not account for the slow downward movement.

I read somewhere that if air has got into the ABS pump you will need to use a procedure (VCDS or similar) which runs the pump to expell the air.

It does, handbrake is almost at full travel before engaging.

Could I have gotten air into the ABS doing what I did? Reservoir never got low.

Would air in the ABS cause the sinking pedal?

Will look at getting VCDS, though I do have an OBED scanner. Can I run the ABS without VCDS?

Set the handbrake cable correctly (from memory is only 1mm gap at the caliper end) then see if you still have a problem.

Set the handbrake by tightening the bolt under the console or by another method? Cheers

So I did both, pumped brake many times, let off the brake, actioned the handbrake many times both with a decent amount of force. No change, it does feel like the front calipers are grabbing but the rears are taking a lot longer travel to activate.

Typically the handbrake should start to hold at 4-5 clicks of the ratchet. As said above you can also adjust at the handbrake compensator under the rear of the central console but on some trim levels it is a long winded job to gain access.

9 hours ago, Karlswat said:

So I did both, pumped brake many times, let off the brake, actioned the handbrake many times both with a decent amount of force. No change

This action will not do anything. It is the handbrake cable length that needs changing at the caliper end or under the rear of the central console.

Ok handbrake adjusted from underneath console. Engages in 4 clicks. A very slight improvement on pedal height

Had similar problem on mine and suspected air somewhere that wasnt coming out with manual bleeding. I got a Gunsons pressure kit and after a while a large bubble came through and brakes were back to normal. Not sure where the air was trapped but definitly not ABS as kept fluid high at all times. Wonder if theres a brake compensating valve for rear it was stuck in.

Alasdair

@Alasdair1 you had the sinking pedal? I can try bleed again. Though I’ve done every wheel with the gunsons. Maybe it’s just stuck somewhere

My pedal seemed soft and sunk a bit but difficult to tell if it was sinking or just spongy. It didnt feel right. If you used a gunsons kit I would have thought it would have cleared the air unless its stuck in ABS and may need VCDS to bleed properly. Check every one for slight leaks as well as flexi/brake lines etc as a slight leak somewhere will cause the same effect. It may not leak until under pressure.

Alasdair

Clamp the flexi hoses one at a time, see what it does to the pedal feel. That can help you find which wheel has the issue, or if it's a whole system problem (which would point to the master cylinder).

I'm a big fan of pre-filling calipers before connecting them, and using a vacuum bleeder rather than a pressure bleeder.

Edited 13 April13 Apr by StevesTruck

Update on this, I got my local garage to do a renewal of brake fluid. This seems to have fixed my problem, no issue with the master cylinder. Just some air left that I couldn’t shift