binding front brakes MG ZR

[rapidyellow]

advice needed, I have bought another ZR and on the road test it had a binding front brake [more near side than off], I have replaced the pads and the guide / slider pins and metal guides that the pads fit into were lightly greased with lithium high temp stuff, the pistons were a bit resistant to go back [ I think, not hard, I didnt pay a lot of attention but I have done this job many times and it wasnt THAT hard to push back compared to others] but they did push back, anyway the nearside brake was still binding





onto this evening and a chance to take another look

so I have had the hottest side [ns] apart and the piston pumps out of the caliper ok, and will press back in with a normal amount of resistance, fitted back together and with the pedal firm there is drag on the disc but what I would call a normal amount, you can turn the hub by hand with the wheel off [brakes obviously cold]

visual and physical feel of the flexy showed it to be in good, pliable order

I undone the nuts holding the master cylinder about 4mm, to see if the piston was being pushed with the brake off, dabbed the brake, still slight dragging.


so I have been out and have done done about 4 miles in it, not been hard on the brakes and they were smoking and stinking when I got back and its still binding quite bad and with a loss of feel [faded probably], it obviously gets much worse when the brakes are hot, possibly binding the same amount as it did with the old pads in, just the fronts but mainly the near side

can only just push the car on level tarmac with handbrake off


my step son says the brake fluid looks really dark, could it need changing?


wishing I hadnt bought it now thinking that sorting a binding front disc would be an easy fix


help!!

[Kieran]

Do the pads move freely in the carriers?

It's usually corrosion behind the caliper piston seals that cause dragging. The furry corrosion cause the rubber seals to grab the piston tighter, meaning they are more reluctant to release.

[rapidyellow]

Aug 21, 2015 20:23:20 GMT Kieran said:

Do the pads move freely in the carriers?

yes, no probs there

It's usually corrosion behind the caliber piston seals that cause dragging. The furry corrosion cause the rubber seals to grab the piston tighter, meaning they are more reluctant to release.

thanks for the suggestion, I did wonder that thats why I took them back apart and checked the piston pumped out, and pushed back in, and that test showed them to be ok, not rough at all either.

[Midas]

Even good looking flexi hoses can break down internally which can cause a non-return valve effect, I think I'd start by changing the flexis and using the opportunity to completely flush the old fluid out in the process.

[swampy76]

As said by Midas flexi can break Down internally and look fine on the outside.

I did have an issue similair to this on my 406 coupe , turned out to be the servo itself

[820]

I would replace the caliper and fluid, it is not unusual for these calipers to leak or stick.

[optimusprime2]

My friend had problems like this and we found it was the flexi hose .He was clamping it up so tigh he ruptured the rubber flexi pipe inside .Pressure going on but would not let the fluid return That might be why the fluid is black as its broken down inside

[stonyray]

As said, got to be the flexi hoses.

Common problem on fords. Not that expensive on the MGZR/Rover 25.

[ChasR]

I've never had a one way valve flexi issue on the 4 Mondeos that have been though our hands ; they all collectively have over a million miles on them too, or on the Focus, Kas or Escorts either . I have not had the best of luck with pattern flexi hoses with the age ageing prematurely or breaking at the end after around a year of use, leaving me to often go genuine or for braided items .

However, one way you could potentially rule the flexis out (although it is not guaranteed) is to see if the pistons go back easier with the bleed nipples slacked off a touch, or by removing the hoses as well and seeing if they become miles easier; I would expect less resistance than if the pistons were hooked up to the brake system, but not much less.

I'd be tempted to say new calipers in your case. When I switched the Escort calipers with no hoses attached I could still with enough force push the caliper piston back in by simply using the disc.

[rapidyellow]

right, I have taken the calipers off the green car and refitted them to the grey one, and all seems fine, I didnt take the brake flexys because if after changing the calipers they were still sticking, I would have bought new flexys, but all ok on the short drive I have just been on.