19 replies to this topic

[Duncy H]

Does anybody have some handy hints for removing a piston from an ap caliper? The seals have had it and need replacing. I have one side out which is on the side of the bleed nipple but can't manage to pull out the other side.

Thanks in advance for any help.

P.s. will the average brake centre type place have seal kits/calipers the same as i have off the shelf?

[bmcecosse]

Well - my method only works if both pistons are in place...... my grease gun connector thread fits the hose connection perfectly (3/8 UNF) - pump in grease and when one piston starts to move, clamp it and keep pumping till the second piston moves. Then move the clamp (if necessary) and pump away until the piston opposite the hose connector falls out - remove the grease gun and put a steel rod through the hose hole against the piston and push it out using a vice. Obviously - ALL the grease must be completely removed before rebuilding. And no - I think seals only from Mini specialists - and DO get stainless pistons too!

[L400RAS]

How much of the piston is exposed? I used mole grips and large stilson pliers to twist and pull the remaining piston out. Only use this method if you are replacing the pistons, as it will scratch the sides...
If there is not enough to grip onto, reconnect the calier to the car and squeeze some out. You may have to replace the removed piston...

As bmcecosse says, choose stainless pistons.

Edited by L400RAS, 17 July 2011 - 02:05 PM.

[Duncy H]

Well - my method only works if both pistons are in place...... my grease gun connector thread fits the hose connection perfectly (3/8 UNF) - pump in grease and when one piston starts to move, clamp it and keep pumping till the second piston moves. Then move the clamp (if necessary) and pump away until the piston opposite the hose connector falls out - remove the grease gun and put a steel rod through the hose hole against the piston and push it out using a vice. Obviously - ALL the grease must be completely removed before rebuilding. And no - I think seals only from Mini specialists - and DO get stainless pistons too!

Cheers for the help, I got the first one out with an air compressor, i'm going to try and pop it back in and clamp it down. With what i don't know though, lots of cable ties might do the trick Looks like i will have to make another long trip to a mini garage then (N)

[Duncy H]

How much piston is exposed? I used mole grips and large stilson pliers to twist and pull the remaining piston out. Only use this method if you are replacing the pistons, as it will scratch the sides...

As bmcecosse says, choose stainless pistons.

Maybe about 3mm. I might give it a go but ideally I'd have liked not to replce the piston.

[bmcecosse]

The old pistons are best thrown away.....

[Duncy H]

The old pistons are best thrown away.....

If that's the case then I'll not hold anything back getting it out then.

[bmcecosse]

http://cgi.ebay.co.u...=item5882118d9a

But check if these are the correct diameter before buying - because his listing is confusing. If they fit a Mini - they won't fit a Cooper S for example!

[Duncy H]

http://cgi.ebay.co.u...=item5882118d9a

But check if these are the correct diameter before buying - because his listing is confusing. If they fit a Mini - they won't fit a Cooper S for example!

I don't think they are the correct ones, I'll get my ass over to a mini place tomorrow and make sure i get the right onesw with my caliper in hand. Thanks for all your help, it's really errrr helped

[bmcecosse]

I think they ARE the right ones - but just check diameter with him before parting with cash!

[AndyR]

Just my method of getting out the pistons............if you are interested in a cleaner version of the grease gun above and a less dangerous version of the high pressure you mentioned with the air compressor

I took an old caliper hose and plugged one end into the caliper (obviously) and the other end stuffed into a hand bicycle pump - one with a locking presta valve attachment. Then carefully increased the pressure until the piston moved to nearly popping out. Then i used a wood workers "F" clamp to prevent that piston from flying out and continued increasing the pressure until the opposite piston came out - it still does fly out at quite a speed so you still need to be careful but not as dangerously fast as will a compressed air gun. The first piston can then be removed by hand as its far enough out to just wiggle out.

Andy

[bmcecosse]

I have tried with air - and never had any movement whatsoever. I guess your's weren't 'stuck'.......

[AndyR]

True....i have never had to remove "stuck" pistons, i guess when that happens more drastic (less compressive) measures have to be taken.

Just thought i would add a way that i thought could be done with tools that most households will have and can be done effectively and safely. Albeit in less drastic cases.

Andy

[Big_Adam]

My engine guy always suggest pumping grease into them and forcing them out.

[Duncy H]

It's not that it is stuck (I don't think) as it is just the seal that is perished and hasn't been stood or whatever. It's just that it's tricky to get out. Anybody got any tips for putting the pistons back in too?