Went to the builders yard this morning and when i got there i could smell cooking brakes. Got out for a look and passenger front wheel was smoking hot.

Got it home driving slower and using the brakes as little as possible, and i've pulled the corner apart hoping it was just a stuck slider, except i cant actually see anything wrong.

sliders are free, pads werent even stuck in the carriers. I lifted the pistons boots and the pistons are shiney clean. I then got a G clamp, and if i push one piston in, the other pops out and vice versa, very little force needed, suggesting the pistons themselves are free. Now heres where it gets really odd...

I put a block of wood in the caliper leaving about 10mm of space, jumped in and pressed the brake pedal, in an attempt to push the pistons out some more, so i could check for rust, except nothing happened. The space remained at 10mm. I turned the ignition on and charged up the brake pump and properly heaved on the pedal... same thing.

Got a chunk of metal across both pistons and managed to force them both back 5mm or so with the g clamp. Reinstalled the caliper on the car. Since i pushed the pistons back theres now a 5mm gap between the caliper and pads. Stomped on the pedal as hard as i could inside the car, but the gap didnt close.

So what on earth is going on here!?!

One minute they're stuck on, and now they;re not getting any pressure at all?

Corrosion inside the pipes & rust particles blocking the flow ?

I'm wondering if its a collapsed flexi? They look pretty old.

My money would be on a collapsed flexi. Usually makes its presence felt after the flexi has been clamped for work to be done, but there's nothing to say it can't happen with an old hose. Particularly on the front where it is constantly bent back and forth when steering.

If not a collapsed flexi could it be a problem inside the ABS unit?

Lpgc wrote:

If not a collapsed flexi could it be a problem inside the ABS unit?
Yeah that was the only other thing that was on my mind...

I drove it up and down the drive a few times after putting it all back together. brakes feel normal, but the passenger caliper is still loose and not even touching the pads.

I think i'll order a pair of front flexis and go from there.

okay sooo its still broken.

Swapped the passenger front flexi this afternoon. Was slightly worried to see zero fluid coming out of the line when i disconnected it from the hardline. Put the new line in and pressed the pedal and... nothing. Exactly the same as before, no pressure getting to the caliper.

I then grabbed the old flexi i removed and tried to skoosh some WD40 thru it, and sure enough, its not blocked and the spray comes flying right thru.

So something weird going on inside the Wabco unit?!

I connected the nanocom to see if there were any faults, and there doesnt seem to be any.

On the outputs page there are 8 options, front right inlet and outlet valve, front left inlet and outlet valve etc for all four corners.

No idea what they do but i decided to start pressing things and discovered a discrepancy. If i apply some brake pedal and click any of the four inlet valves, i get a small kickback from the brake pedal. If i then click the corresponding outlet valve, i hear a distinct click from the Wabco unit, except for the front left... For the front left i get no click when i press the outlet valve.

The inner workings of the Wabco are a bit of a mystery, but it would seem that its faulty in some way?

Ordered up another Wabco unit from the bay and started the swap procedure today.

Removing the modulator is fairly straightforwards if a little awkward, however i got hit with a bit of a snag... The top bolt that holds the modulator to the bulkhead was properly stuck. After heaving on it i got it moving and eventually it worked its way out of the nut, but wouldnt move any further. Corrosion between the ally housing and steel bolt.

I ended up managing to remove the L bracket between the modulator and bulkhead, which was a proper pig as the bracket goes in before the steering column, so getting at the two nuts requires lots of creativity...

With that off, the modulator came out and i managed to free the bolt off with a punch and big hammer. Oddly the bolt actually appears to be slightly bent (possibly due to me beating on it...), so i'll need to sort another one.

Then it got dark so i gave up for the evening.

I did discover something odd, with all the brake lines removed, the pedal on the old modulator still wouldnt depress... It moved about 1cm then went solid. I would sort of expect to have got a long spongy pedal with all the lines removed?

When i got it on the bench and prodded it some more, eventually i opened the bleeder for the master cylinder. When i did that and pushed the pedal fork, fluid shot out of the bleeder and the rod now moves.