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Tin top just failed M.O.T on front OS Brake binding
omega0684 - 18/11/10 at 03:51 PM

hi guys,

as per title really, tin top has just failed M.O.T on a binding front O/S brake, what are possible causes so i can investigate (im presuming caliper piston) and resolve? the car doesn't pull to the right under braking though.

All the best

Alex


jossey - 18/11/10 at 03:57 PM

strip it down and put copper slip on the bits and try lossen the piston. if you cant just get a new caliper set.

get a bleeding kit if your stripping it down. they are well helpful.....


dave


Stott - 18/11/10 at 03:58 PM

Clean the recesses that the pads slide around in on the calliper and also the calliper sliders, clean em out and put a touch of silicone grease on them (assuming they are the ford type of sliders)

Clean around the calliper seal as it's best practice while you're there.. That should free it up some.

You can assemble it without the pads and check the freeness of the sliders to be sure before going for a retest.


HTH
Stott

EDIT: I meant clean around the calliper dust seal, not the piston seal. I wouldn't visit the calliper piston itself before it was all thoroughly cleaned out and checked as above.

[Edited on 18/11/10 by Stott]


BenB - 18/11/10 at 03:59 PM

Garage owners got a big overdraught and needs the work? Just kidding!
Otherwise it's worth taking the caliper off and seeing what kind of shape the guide pins are in. If it's just one sided it's not an MC or servo problem so if the pins are okay and the disk isn't warped think caliper piston.


carpmart - 18/11/10 at 04:01 PM

Not sure on the car (?) but check the sliding mechanism that the caliper moves on. Take the brakes apart and give all the parts where the pads sit and the parts where the sliders operate a good wire brush the use judicious amounts of copper grease in the areas which require.

Since you have the pads out as your doing this job, carefully clean the edge of the piston and check for pitting and corrosion. You should carefully try to push the piston out (so you can clean them well) by using the brake pedal, but put something in the caliper to make sure you can't pop the piston out! Also watch that you don't damage the dust seals as you clean! As you retract the piston, make sure that it moves reasonably freely. Repeat on the 'good' side!

That's what I would do anyway!


carpmart - 18/11/10 at 04:02 PM

I'm too bloody slow at typing!


adithorp - 18/11/10 at 04:25 PM

In order of popularity...

1. Pads sticking/rusted in the carrier... clean the rust off both pad and carrier and (lightly) copperslip contact points.
2. Caliper sticking on sliders... clean pins and lube with silicone spray or red rubber grease. Also with ally calipers (late ford rear mainly) we're getting corrosion between the caliper and the rubber bush that the pins go through causing tightness... pull out the rubber clean and refit.
3. Piston sticking... pump out, clean and press back, repeat. If that doesn't cure strip down, fit new seals, etc.
4.Blocking flex hose. Rare but do see occationally... fit new flexis

You often don't feel pull when driving with a sticking brake. Odd but true.


britishtrident - 18/11/10 at 04:47 PM

Don't use WD40 it may contain silicones but most of it is kerosene --- even a tiny trace will turn the seal hard.

Usually sticking front calipers are down to the pads or guide pins seized/jamming or the callipers seals have lost elasticity.


peter_m7uk - 18/11/10 at 09:25 PM

quote:
Originally posted by omega0684
hi guys,

as per title really, tin top has just failed M.O.T on a binding front O/S brake, what are possible causes so i can investigate (im presuming caliper piston) and resolve? the car doesn't pull to the right under braking though.

All the best

Alex


Maybe daft question. but how worn are your discs and pads? I failed on the same thing in September, put new discs and pads on (they were fairly worn down) and it sailed through.

Pete