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Discussion Starter #1
So, I have just spent two hours unsuccessfully trying to change the pads on my rear disc brakes. The problem is that the new green stuff pads are much thicker than the ones I am taking out and I am unable to get the piston to retract. I released both pins, removed the spring and took the pads out. Whatever I did I couldn't get the Pistons to retract, even when I losened the bleed valve. I detached the calipers to try and get more leverage, but to no avail. I also tried to take the calipers apart, but I was unable to take out the two outside bolts as the rear part is recessed and I was unable to get a purchase on them. I presume I am just being dumb as this must be something most of the members on this forum have done without the need to post for help, but any insight would be gratefully received.
 

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Its designed to slide in while the caliper and pads are in place so no need to remove anything
 

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I just did a rear end rebuild and found my calipers seized solid, on a car used every few days and bought with a MOT! If the pistons are that hard to move then I suspect there is something wrong. I got brand new ones and pistons slid back by hand easy. I replaced the rear limit valve too...brake stuff was never made to work for 35 years without some work.
 

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If the pistons are that hard to move then I suspect there is something wrong.....
agree, the pistons should slide back easily (that caliper retractor above that I also have should have no problems, if it does your pistons are seized)

@ Mattystar: what do you mean by "I also tried to take the calipers apart, but I was unable to take out the two outside bolts as the rear part is recessed and I was unable to get a purchase on them"

you are not trying to split the calipers in half? don't do that unless you want a full rebuild on your hands.
Are you saying the calipers are off the car and the pistons won't budge? in or out?
 

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Discussion Starter #7
agree, the pistons should slide back easily (that caliper retractor above that I also have should have no problems, if it does your pistons are seized)

@ Mattystar: what do you mean by "I also tried to take the calipers apart, but I was unable to take out the two outside bolts as the rear part is recessed and I was unable to get a purchase on them"

you are not trying to split the calipers in half? don't do that unless you want a full rebuild on your hands.
Are you saying the calipers are off the car and the pistons won't budge? in or out?
Luckily the car clearly realised what an idiot I was and so stopped me from splitting the calliper! After much frustration I tried the front instead and ended up taking the whole calliper off and pushing the piston back with a g clamp. Tried the other front calliper and couldn't disconnect as all the nuts I needed to undo were inaccessible. Ordered one of the spreaders that Joe and you have (spider) which arrives today. Subject to that being the fix I need I am going to bleed the brakes and then hope all is sorted.
 

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Discussion Starter #9
even if you get the pistons to retract, then make sure they move back and forth smoothly
Looking at the trouble you are having, I can't imagine your brakes were any good at all...were they?

this is an excellent write up on caliper restoration (the greasegun trick he uses is because he is splitting the calipers anyway)

Restoring Some 105/115 Rear Calipers... - Alfa Romeo Bulletin Board & Forums
The brakes were poor, hence the new pads and bleeding. The spreader tool has been a revelation and has saved me significant time. I have now unfortunately come across one properly seized piston on the outside front right calliper. I realise that I may need to redo the brakes at some point in the future (e.g. strip them down and rebuild them), but I need the car for next week and so ideally would be able to get it back on the road today. Any tips on how to unseize a piston, does it require disassembled of the calliper?
 

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Any tips on how to unseize a piston, does it require disassembled of the calliper?
perhaps put one new pad in the good side and a thin piece of wood in the stuck side and use pedal pressure to move the piston out, not back, this might unstick it, then try wind it back...

if it is not hooked up you could try compressed air to move it out (important: you need to put a block between the pistons or they will become missiles!); if it moves out a bit, then see if it winds back.

tbh though you are looking at a rebuild.

'the Nutty Professor' here has a video with some ideas...

https://www.youtube.com/watch?v=qc4zlGaJgoA
 

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Discussion Starter #11
Thanks Spider, after a long afternoon I have reassembled everything (had to put one old pad and one new pad) in the front right caliper and I bled the system. The brakes are better and amazingly don't pull to one side, they definitely still need to be rebuilt, but I will leave that for when I have more time.
 
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