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Omega Help Area => Omega General Help => Topic started by: ScottieMV6 on 12 April 2010, 17:30:00

Title: Seized piston in rear brake caliper!
Post by: ScottieMV6 on 12 April 2010, 17:30:00
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?
Title: Re: Seized piston in rear brake caliper!
Post by: tigers_gonads on 12 April 2010, 17:32:42
can you get a bar in there and lever it back ?
Title: Re: Seized piston in rear brake caliper!
Post by: Entwood on 12 April 2010, 17:34:21
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 ....  :)
Title: Re: Seized piston in rear brake caliper!
Post by: ScottieMV6 on 12 April 2010, 17:38:11
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. :-/
Title: Re: Seized piston in rear brake caliper!
Post by: KW on 12 April 2010, 17:39:08
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.
Title: Re: Seized piston in rear brake caliper!
Post by: ScottieMV6 on 12 April 2010, 17:42:32
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. :y
Title: Re: Seized piston in rear brake caliper!
Post by: Andy B on 12 April 2010, 17:54:13
Quote
....

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

Can you get a decent sized G clamp in there?
Title: Re: Seized piston in rear brake caliper!
Post by: CaptainZok on 12 April 2010, 17:58:53
http://www.machinemart.co.uk/shop/product/details/cht268-disc-brake-piston-spreader/path/automotive-tools

How about one of those.
Title: Re: Seized piston in rear brake caliper!
Post by: Road Hog Mad on 12 April 2010, 17:58:59
a spray of WD 40 in that circle thing on the caliper
Title: Re: Seized piston in rear brake caliper!
Post by: ScottieMV6 on 12 April 2010, 18:23:47
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 :y
Title: Re: Seized piston in rear brake caliper!
Post by: Cliffo B on 12 April 2010, 19:06:02
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 :'( :-/ :o 
Title: Re: Seized piston in rear brake caliper!
Post by: Cliffo B on 12 April 2010, 20:03:46
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 :y :y 
Title: Re: Seized piston in rear brake caliper!
Post by: eddie on 12 April 2010, 22:27:52
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
Title: Re: Seized piston in rear brake caliper!
Post by: KW on 12 April 2010, 23:13:10
Quote
a spray of WD 40 in that circle thing on the caliper
Possibly not a good idea as WD40 destroys rubber in seconds.
Title: Re: Seized piston in rear brake caliper!
Post by: feeutfo on 13 April 2010, 08:04:23
may well have to pump the piston out altogether and replace the seals.

Is the piston going back in square to the caliper?
Title: Re: Seized piston in rear brake caliper!
Post by: ScottieMV6 on 13 April 2010, 14:14:43
Thanks for all the tips. Now sorted. SWMBO applied light pressure to brake pedal while I eased the piston back and forth. Finally went straight back in :y