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[ScottieMV6]

Replacing th rear brake pads for MOT. Easy job I thought but typically nothing is ever as easy as I think it will be

Offside changed no problems but on the nearside one of the pistons is seized and will not push back into the caliper. The only thing I can think of is removing the caliper and servicing it on the bench (not easy as the nut that holds the pipe on is rounded).

Does anyone have any "tricks" that I might try first?

[tigers_gonads]

can you get a bar in there and lever it back ?

[Entwood]

I'm assuming you have released the bleed screw, I use a large pair of "plumbers pliers" tomove the caliper pistons. thre is a nice flat on the back of the caliper and a large pair of pliers reaches across both sides of the piston to keep it flat ... good squeeze and in she slides .... 

[ScottieMV6]

I have released the bleed screw and have been using a large flat bar (it reaches right across the piston) to try and move it but it will not shift. :-/

[KW]

Remove caliper body from hub assembly, insert old pads back in caliper to act as spacers, have someone press VERY gently on brake pedal to move piston outwards by a millimetre or so, then secure caliper somewhere and push piston back using a pry bar between the old pads.

If piston appears stiff going back in, use a pair of water pump pliers to rotate piston back & forth while exerting slight pressure with the aforementioned pry bar.


PS

The above advice assumes you have (at minimum) removed the cap on the brake fluid reservoir, but ideally have slackened off the bleed nipple on the caliper you are working on when attempting to push the piston back.

[ScottieMV6]

As said I have slackened the bleed nipple and I did have the cap off the reservoir too.

I will give your suggestion a try tomorrow KW and see what happens.

[Andy B]

....

Does anyone have any "tricks" that I might try first?

Can you get a decent sized G clamp in there?

[CaptainZok]

http://www.machinemart.co.uk/shop/product/details/cht268-disc-brake-piston-spreader/path/automotive-tools

How about one of those.

[Road Hog Mad]

a spray of WD 40 in that circle thing on the caliper

[ScottieMV6]

Andy - I would suggest not, not enough room

Captain - Don't really want to spend £23 on something I might only use once.

RHM - Plenty of plus gas already used

[Cliffo B]

Sorry to have to say that oil based products and brake fluid definetley dont mix you must never allow oil of any sort to come in contact with rubber brake pistons they soften and swell could be whats happened :-/  

[Cliffo B]

Just remembered Scottie, I think the only common cleaning agents that can be used on brake parts is brake fluid itself or meths, I hope this helps  

[eddie]

I had same problem on  a front caliper. by removing the outer pad and dropping the caliper back over the disk I was able to pump the piston out a bit further. Plenty of silicon grease under the rubber boot on the piston surface and then used a Ford rotary retractor to squeeze and twist the piston back in.
I did this a couple of times to lubricate and free up the piston.  HTH.

eddie

[KW]

a spray of WD 40 in that circle thing on the caliper

Possibly not a good idea as WD40 destroys rubber in seconds.

[feeutfo]

may well have to pump the piston out altogether and replace the seals.

Is the piston going back in square to the caliper?