Front N/S brake grinding

[dougie212]

Right.... update......... just took the wheel off... doused all 4 bolts in WD40. After some work (and a little persuasion) the slider pins came out. The rear most was an absolute nightmare to get out. Caked in muck. They have both been cleaned and copper greased. The 2 carrier bolts are a little more challenging. It would appear that some heavy handed oaf has already attacked the bolts with everything in their armoury and rounded them off to the point that I don't even think mole grips will help.... Does anyone have any ideas what to do with these 2 monsters?? I am confident now that the slider bolts are the problem... When I drive I do get the grinding noise, but it changes and gets worse when the brake is applied, which suggests that the piston is moving. The noise eases when my foot is taken off the brake. Ive not been able to get hold of any pads so have put it back together. New pads and disc in order.
My questions I guess are does the above seem right, the piston etc.... and what do people suggest to do with the mashed carrier bolts please?
Thankyou!!

[Anton]

The last time I had a bolt that was mashed up like that, I took a cheap single hex socket that was 1mm too small and hammered it on. Undid the bolt and then put it in a vice, and used another bolt to hammer the first bolt back out.



Other options are to cut a slot in it with an angle grinder and try a really big screwdriver, or weld another bolt onto it (the heat of doing this often helps too).

[dougie212]

Thankyou. I'll try the smaller socket. Maybe hitting that on will shock it a bit too as I think they are really tight and seized. The slider bolts were pretty seized up but they eventually came out but these have been attacked and some and not even my mole grips seem to want to help them. Not got a welder sadly. Does my theory about the piston working as the noise changes when I press the pedal seem right?

[Anton]

I'm afraid it's not that simple - the piston may be partially stuck, and not backing off properly when you let off pressure - but normally when they stick, you find the vehicle pulling to the opposite side under braking.

It's impossible to tell. All I can really say is that money spent on reconditioning your brakes is money really really well spent.

Pull them, clean them, check the pistons and caliper bodies for scoring and pitting. If there's pitting, throw the part with pitting.

I got new seals and pistons when I did mine, painted them to protect them, and I've had perfect brakes ever since

[dougie212]

Are the callipers serviceable then Anton? I had an MGZS that had a caliper totally seize and I was absolutely hung out to dry with that as it wasn't serviceable allegedly...

[Anton]

Well, "servicable" means different things to different people.

To me it's anything I can take apart and repair, in which case calipers are serviceable as long as there's no pitting or scoring of the inner surface the piston touches. Even more so if the piston is clear of pitting and scoring.

To others "servicable" means "economic to repair" which, depending on the hourly rate being charged, could mean that nothing beyond an oil change is "serviceable".

I serviced mine just fine, including a set of Rover rear calipers (same as MGF rear calipers, fairly sure even the same as Mgzs rear ones)

Check my build thread for a few details.

[dougie212]

hmm. maybe when I get the wheel off again I'll try pushing the piston back, see if it goes in.. A large G clamp do the trick? Old pad over the piston and tighten?

[Anton]

That's what I do! But inspect the piston first. If the piston is pitted or scored, replace it. Get new seals too.

I use brakes international when I rebuild mine.

I would suggest that if you need to do one, do the opposite side at the same time. It's worth making sure your brakes are in good condition and that they "match" (i.e. you don't have to worry about the other side seizing up 6 months from now).

[dougie212]

Ok... the one thing Im just a bit worried about is inspecting the piston... How do i pull it out to inspect it? will it twist slightly. I looked at the edges of it yesterday and all seemed good with that but the piston was pretty much in the caliper. I looked at the rubber around the edge of it to and that all looked good but will inspect properly... just interested to know how the piston is to come out.

[Anton]

I used compressed air and a block of wood.

At least, I used a block of wood with the second one after the first one fired the piston across the front garden...



That trick won't work for Rover rear calipers because of the handbrake mechanism. But it worked for me with SJ calipers and a set of Vitara calipers. I used a bleed valve and modified it into a kind of air adapter.

I've also wound pistons out manually, but that only works for SJ Aisin calipers (might work for Jimny ones, or SJ Lucas-Girling calipers too, but probably not GV calipers)