Failed MOT (never made it) - help!

[cuneus]

Car started but would hardly budge - tried pumping brake pedal and drove backwards and forwards a bit - no joy

Have now jacked front - OSF wheel stuck - have taken wheel off. Any ideas where to go from here?

[adam quantrill]

Get a few G clamps (e.g. woodworking ones) and get them on the plates on the brake pads.

You should then be able to push the pistons back in a little and free it off.

Then remove the pads and push the pistons back in fully, they should free up.

I usually keep some old fully used pads that I can put in and wedge the pistons back without damaging the faces.

[philh]

might be collapsed flexible pipe, if the inside collapses it stop the fluid returning.

[adam quantrill]

True - if so you could open the bleed nipple to allow the pistons to return - that will help diagnose the problem too.

[cuneus]

Thanks a lot - update tomorrow!

[The Hatter]

Same front brakes as mine...

If it's the same problem as mine, it's likely to be corrosion on the piston bores of the calipers between the dust seal and the main seal. There might be some corrosion on the pistons and if you're lucky cleaning that off will fix it enough to get you going, otherwise it's a caliper rebuild.

If you get the pads out (brute force I'm afraid) you can put a thin piece of wood between the piston and the disc and then push the pistons out with the brake pedal to check.

The dust seals are a sod to get back on too...

[honestjohntoo]

It's not for your car, but the stuff at the foot of page 5 of the pdf available from this link explains what seems to have happened to your front brakes.

http://www.vintagemodelairplane.com/pages/Download...

[cuneus]

The rather mundane update is the only clamps I have are far too long or far too small - so new tool ordered

[cuneus]

Opened the bleed nipple:



and I can now turn the wheel - thanks

I have cleaned up the disc (which didn't seem bad). Is it just a case of reassemble and hope?

[blaineuk]

Do the pistons now move freely?

[TOPTON]

cuneus said:

Is it just a case of reassemble and hope?

Nope, I would be stripping the calipers and looking at the pistons to see why they stayed stuck out and locked the wheel.
They may stay free for a while if left now, but it will happen again. More probably, if left like that the brake will start binding, overheat and possibly cook itself

[cuneus]

Hmm

I have removed the inboard pad which had plenty of room

The other one is very tight - read I cannot get it out at the moment!

Any tips for extraction?

[adam quantrill]

You could try rotating the disk (might need a big lever between the studs). Otherwise the piston is stuck. Can the caliper be moved now one pad is out? Might give enough room to get the pad out without damaging it, then follow the advice about cleaning up the pistons.

[cuneus]

I managed to tap the stuck pad out with an aluminum bar from the other side

There is virtually no wear on it (the bottom one in the pic) suggesting it has been like that since the caliper was rebuilt 4 years ago

which leads me onto removing the caliper: the 2 bolt heads which I need to undo are fouled by ears from the bracket supporting the
brake pipe ??

[Wedg1e]

cuneus said:

which leads me onto removing the caliper: the 2 bolt heads which I need to undo are fouled by ears from the bracket supporting the brake pipe ??

Lever or tap them back with a screwdriver, tap back into place on refitting. They're lock tabs to top the bolts unscrewing. Ideally you'd replace them at every rebuild but I've never seen it happen. There must be a shed somewhere with millions of them in, unsold...

[TOPTON]

They are not fouled by the bracket, it is supposed to be like that. They are tabs bent up to stop the bolts coming undone. Tap them down flat, but remember to bend them up again when refitting

ETA great minds think alike and fools never differ

[cuneus]

Thanks again!

[adam quantrill]

I would tap the lugs back with a screwdriver and then, oh, err... ;^)

[cuneus]

Took the advice and once I'd found the breaker bar:

Should the pistons slide in and out easily by hand? (cos they don't)

[adam quantrill]

Not quite - you have to be careful to push them in square and even then it might be a fair effots with both thumbs to push one back in.

Don't forget that under hydraulic force the pressures are quite high (at least if the servo is working OK) so they will push out. The only trouble comes when they won't knock back in fraction of a mm necessary to stop the pads binding when the pedal is released - as you have found. I would investigate under the rubber seal of the one you found was stuck, and leave the rest alone.