Freeing up seized rear brake calipers - any tips?

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Oscar
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Freeing up seized rear brake calipers - any tips?

Post by Oscar »

Hello

One side of at least one caliper, if not both, is seized. I need to free them off, change discs and change pads. I might try and do this myself, if anyone can offer a few pointers. All tips gratefully received.

Oscar
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AndersDK
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Post by AndersDK »

Remove the friction pads, then insert 2 pieces of metal sheet if you need to protect the discs.
Refit (disc if removed) roadwheel - then raise/set the suspension height to maximum (to get brake pressure on a dangling wheel) - have engine idle and apply brakes several times until pistons have worked themselves out. Now grease the exposed piston circumference using any type automotive grease.
Lever the pistons back into the caliper halves using a large screwdriver, then work the pistons out again etc. to ensure the pistons are really freed up in the bores.

Do ONE side at a time :shock:

Once the pistons are free to move, you are ready for a rather easy rear brakes overhaul.

TIP : if you cant make the brake disc free the hub, then refit friction pads and roadwheels - but leave wheelbolts loose by ½ turn.
Then VERY CAREFULLY take a short drive around the block using the brakes abruptly several times. Finish off by driving slowly back and forth stamping the brake pedal. That should loosen the most stubborn wheel or brakedisc from the hub.
You can do both sides wheels/discs in one go, but dont do all 4 wheels - as that can make for some very strange behaviour from your car (and any PLOD around) :lol:
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Oscar
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Post by Oscar »

Hi Anders!

I knew you'd answer. Thank you for a very helpful and clear explanation.

Regards

Oscar
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Post by DLM »

Both rear calipers on Silver Machine had one side seized earlier this year, so something had to be done. On the good side I had the very rare luxury at present of both a space to work and a couple of days time, but on the bad side there was also a broken-off bleed nipple on one side.

I went for the caliper removal and rebuild route, as I managed to cobble together enough spare bits from my parts pile (backplates & clips), Tom donated a caliper half for the side with the broken-off bleeder, and I was able to buy or customise replacement nuts/bolts for the corroded-on ones holding the backplate in place (once I'd broken the orginals despite copius amounts of wirebrushing and loosening juice).

If you have to disassemble, beware of:

Rusted-in bleed nipple (at the risk of teaching grandmothers to suck eggs)
Rusted-through backplates (& corroded retaining nut/bolt)
Uneven corrosion on inners of caliper halves (stop pads from sliding)

For once, the BOL (Haynes) was a decent guide, and the note about using a footpump to blow out pistons was spot on - compressed air didn't shift them at all, while stamping on the footpump with some violence did. I had a few secondhand pistons to play with, but don't count on the old ones being 100% perfect. New discs went on and that particular side of things was now all sweetness and light - unlike the other jobs I was attempting to do while I could have the rear end of the car up in the air for a couple of days without disturbance.....
Back on two wheels and pedal power for the moment.
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Oscar
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Post by Oscar »

Well, in no time at all, three months later, a working caliper, two new pads and a new disc have been fitted. Unfortunately, re-reading Anders' message has reminded me that I need to grease the piston circumference, so the roadwheel will be coming off again early on Saturday morning....

It would have been good to have done this BEFORE sending it in for an MoT. It failed on...seized pads and corroded disc. I'm my own worst enemy.

Anyway, another lesson learned. Thanks for help.
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Post by jeremy »

When I picked my BX up from its MOT I was greeted by 'It was leaking from a bleed nipple - and I've tightened it.' - Strangely it was the one I couldn't get undone when changing the brake hoses despite soaking, bashing etc - but I couldn't get it close enough to a power supply at the time to use my MIG on it and had bled the caliper by loosening the hose.
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Post by Oscar »

OK Jon, a bit more work to do then I guess. I'll leave it until end of Feb as Lena is twitching a bit when I mention the car (I gave her a baby to play with - what more does she want?)

New front pads and possibly disks coming up too. Oh well. At least we have the ticket for this year - yippee!
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charlotte001

Freeing up caliper

Post by charlotte001 »

there would have been an easy way.

1. Remove caliper
2. Remove dust seal (if fitted)
3. Fit air pump to nipple switch on (DO NOT have hands anywhere near piston)
4. When piston is out clean the hole with fluid/ Petrol (Not Diesel)
5 lightly (And I mean lightly) clean any rust ouf of the piston hole with some very very fine wet and dry then blow out with air line
6.refit piston seals (always new seals)
7 refit piston making sure you've used some fluid on the piston (must be new fluid)
8 Refit everything and bleed off

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kermit the frog
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Post by kermit the frog »

You won't find rust or dust seals on the rear calipers of a BX as they are
Aluminium.

I also would not recomend getting petrol anywhere near brake components especially the seals which if you are carefull should be removed before cleaning.

A good clean with hot water and washing up liquid will do a far better job.
Just make sure you dry it out well preferably with an air line

And you can't remove the caliper in one piece as it is split and only held together by the locating bolt's
Also the pistons are anodised aluminium as well.
The only good thing is that the halves are interchangable.
The pipe hole and the nipple hole are the same.
so if you have a broken nipple or a siezed pipe you can make up a new caliper from two old ones.

IE : the outer part of a nearside rear caliper can be used to make the inner part of an offside rear caliper and vice versa.

Regards Kermit :) :)
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DavidRutherford
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Re: Freeing up caliper

Post by DavidRutherford »

charlotte001 wrote:there would have been an easy way.

1. Remove caliper
2. Remove dust seal (if fitted)
3. Fit air pump to nipple switch on (DO NOT have hands anywhere near piston)
4. When piston is out clean the hole with fluid/ Petrol (Not Diesel)
5 lightly (And I mean lightly) clean any rust ouf of the piston hole with some very very fine wet and dry then blow out with air line
6.refit piston seals (always new seals)
7 refit piston making sure you've used some fluid on the piston (must be new fluid)
8 Refit everything and bleed off
In relation to a BX rear caliper, this post makes no sense and is wrong in many ways.

Are you just quoting from a Haynes manual? Or possibly something even more useless than that? Given that you've had to ask for advice on how to check your LHM level, and clearly know very little about the hydraulics in a BX, are you really in a position to give advice on how to strip and rebuild a BX caliper?

Again, I'm not trying to be rude, but when seasoned BX owners are making points specific to the BX rear caliper, and then you turn up stating that theres an easier way, and then reel off a "generic" caliper rebuild process, I'm inclined to wonder what you're trying to prove...
this might be a signature
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