Brake caliper problems...

Hi all, hope I can get some advice...

Rear brake discs were knackered on my disco so I have taken off the hub and replaced disc with new. I also need to replace the pads as they are likewise very badly worn.

Problem I've got is with new pads and disc (all mintex) I just cannot get the second pad into the caliper. I expected it to more or less just drop in but there just does not seem to be room...

Wondering if pistons are going back far enough. Should they go back absolutely flush with the inside face of the caliper housing, or do they remain proud by about <1mm even when fully retracted, like mine?

Also, looking at my housing there seems to be a 'false face' on it, like a thin spacer, between the back of the pad and the side of the caliper, with a hole in it for the piston to come through. This is only on the side of the unit. Gentle prying / tapping suggests it may be a bonded part of the unit and not meant to come off - is this normal / standard? (Even if it were to come out if the piston doesn't go back any further it won't make any more useful space.)

Any other hints or tips because I'm just about at my wits end with this and still have the other side of the vehicle to do!

Thanks,

M

pistons should go flush and pads just fit when fullly back usually wise to push pistons back with old disc in place as it doesnt matter if you damage it ,if you push brake pedal so that piston pushes out ,careful not to go too far you can clean piston before pushing back

Thanks James, that explains a lot. I'll have another go tomorrow. I guess if I've been driving around for a while with worn discs and pads the ends of the pistons will have been well exposed a lot of the time, giving them plenty of opportunity to get enough rust on the ends to stop them pushing back. I'll try giving them a gentle clean with some fine wet & dry or similar. Will report back on whether it works or not...

M.

Dont forget to take the top off the master cylinder resevoir so as the fliud can go back when you push pistons back in.

As james said you can carefully push the pistons out using the brake pedal - a bit of wood ( of suitable thickness ) etc placed between disc and piston will stop the piston coming out altogether.
You may find the ends of the pistons quite corroded - when cleaned up the piston should not be pitted etc .
If it is and you force it back it will damage the seal .
When I did this job I replaced pistons and seals . The parts are cheap and you have job done for a long time .

Just to let you know if your changing the piston make sure you measure the old one against the new one, i bought a new piston and seal kit turned out the new pistons were slightly longer than the old ones and would not push all the way in ended up having to put them in the lathe at work took about 8mm off if i remember right

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Thanks all. I've put a brake hose clamp on the hose above the rear dif and am opening the nipple on the brake caliper, in order to avoid any seal reversal in the master cylinder.

I'll have a go at cleaning the existing pistons first, although if I have to I'll replace them. Unfortunately doing that will add a further week to the job as I wait for the stuff to comet through the post (and then no doubt have to go to the sorting office to collect the parcel because no-one is at home when the delivery guy turns up).

Thanks for the warning Discogaz - I think I read another thread about that; something to do with the front caliper pistons being a few mm longer than the rear ones and parts getting mixed up.

M

Discogaz - I say, ol chap, turn orf the "imatit" Tork will you?

The Mad Hat Man said:

I say, ol chap, turn orf the "imatit" Tork will you?

Click to expand...

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You may find you will get the pistons right back it you work them in and out a fee times. I use a big flat screwdriver or a small pry bar to lever them back in, and always remember to have something between the piston and disc when pressing the brake pedal. I didn't do that one time and it was a PITA to get the piston away from the disc!!!

I would also not do it with the clamp on the flexi. When you are working the pistons in and out you need to fluid to move back and forth in the system.

Upon saying that, it sounds a neat way to get rid of the crap fluid and gunk that can sit in the caliper.

One final thing, if you are sending away for more things it is worth getting new nipples and swapping out the existing ones whilst you are in there. They are cheap enough to be almost free.

G

The Mad Hat Man said:

Discogaz - I say, ol chap, turn orf the "imatit" Tork will you?

Click to expand...

Sorry don't know what that means but i'll try, just talking from experience thought it might help

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I was alluding to the spam at the bottom of all of your posts. If you would be so kind as to turn it off, please.

I got sick of ****ty caliper pistons and not going back in, so because i'm too tight to buy a proper tool, made this

now I no longer have to prat about with bars, slip grips, etc. although a G clamp probably would have worked too but this pushes it in more evenly across the piston

The Mad Hat Man said:

I was alluding to the spam at the bottom of all of your posts. If you would be so kind as to turn it off, please.

Click to expand...

Sorry didn't know you could turn that off, think ive found how to sort it though, here goes

just get new calipers, only 30 quid and saves hours of messin bout...


SMC500240 LAND ROVER DISCOVERY 1 300TDi LEFT HAND REAR BRAKE CALIPER | eBay

Spent most of the day pfaffing around with this but have now got both new rear discs on and the hubs all rebuilt and on. Both caliper's are now in a box in the dining room and I will have a proper look at them and see what can be done with the pistons over the next few days. All the pistons are now at least part way out of their holes and some of them do look pretty rusty, so I'll probably be ordering some new pistons and seals. Reluctant to order new calipers as funds are tight at the moment, which is why I'm doing this job myself.

Thanks everyone who has contributed tips and suggestions, I hope I'll be able to contribute something useful eventually.

M.

McBad said:

Unfortunately doing that will add a further week to the job as I wait for the stuff to comet through the post (and then no doubt have to go to the sorting office to collect the parcel because no-one is at home when the delivery guy turns up).

Click to expand...

I used to have my parcels delivered to where I worked, always someone there to receive them and no trips to the post office. Not always practical I know but just a thought

OK, just to complete the story...

On inspection the outer few mm of each piston was quite rusty and pitted after cleaning so I removed them completely (I gently twisted them out with a big pipe wrench, not worrying about scratching them up as they were going to be chucked). They came out without much problem. I removed the wiper seals and fluid seals with a blunt screwdriver and cleaned the bores and seal recesses with brake fluid and cotton buds.

Rebuild with new seals and pistons was again easy. Lubricated everything well with brake fluid. To fit the wiper seals I put the piston in first, leaving it protruding a few mm, then fitted the wiper seal in it's metal carrier and dropped this over the piston.

Next I put a handily-sized brick bolster over the end of the piston and the wiper seal and used a G-clamp to press the bolster and therefore the piston and wiper seal into place. Worked a treat. When the pistons are fully retracted they are exactly flush with the inside face of the caliper.

Refitted calipers to vehicle, fitted brake pads, anti-rattle springs and split pins. Getting the split pins in is a bit of a fiddle but they went eventually. Gently tapping the metal tab on the brake pad back and forth to get the brake pad in the exact right spot helped.

Bled the brakes, put the wheels on and road tested. Seems to go, and more importantly stop. Result.