Seized rear brake calliper piston

jpbdrogheda

I'm looking for some tips on how to fix a seized rear brake calliper piston on an 04 Saab 93. Went to change the rear brake pads today and while the passenger side was a doddle to do i ran into a problem on the rear drivers side. I couldn't retract the piston and it seemed seized. I have the correct retractor tool and it worked fine on the other side.

I dosed it in brake cleaner in the hope it might unseize it but no luck.

Does anyone have any tips on how to fix it? for now i put the old set of pad on. I know thats not ideal. So would be grateful if anyone had any advice on how to retract the piston.

Thanks

CJhaughey

If its seized then it needs to be rebuilt or replaced.
Is it a screw in type piston or a push type? Push types can be moved with a
G-clamp but once you have done so it will need cleaning and rebuilding. Likely its full of rust and corrosion behind the rubber boot on the piston.

jpbdrogheda

Its a screw in type so G-Calmp won't work. Thanks though.

mobfromcork

I had this on a Mazda some time back. (Couldn't push the front piston back in rather than one of the rears that needs a winder.)
I kind of knew I'd probably end up needing a new one so tried a few things first. I ended up forcing it with a g-clamp and it did go after a lot of pressure but when I put it back together it kept binding and wouldn't retract properly. I popped the piston afterwards and it was all rusted/scored where the rubber gaiter had torn.
Had to get a new caliper.

The Sidewards Man

Extract the piston and clean up and grease with red rubber grease. Was the boot on the piston damaged?

biko

Take caliper off and take it apart. Clean thoroughly and grease everything up and see if that works.
If not you may have to get a pro's opinion or simply replace.

jpbdrogheda

The Sidewards Man wrote: »

Extract the piston and clean up and grease with red rubber grease. Was the boot on the piston damaged?

Thanks for the advice. The rubber doesn't look damaged at all. From what i can tell anyway. Do i need any special tools to extract the piston and get it back in place? Is it just enough to clamp the brake hose shut when taking it off?

jpbdrogheda

biko wrote: »

Take caliper off and take it apart. Clean thoroughly and grease everything up and see if that works.
If not you may have to get a pro's opinion or simply replace.

Yeah i might consider taking it off. Or just pick up a second hand one from a scrap yard. Thanks for your advice.

shietpilot

If there's any roughness to the piston there is no point in replacing the seal as the rough piston will just destroy the seal again.

I wouldn't waste my time and just replace the whole caliper after you check what it looks like!

CJhaughey

shietpilot wrote: »

If there's any roughness to the piston there is no point in replacing the seal as the rough piston will just destroy the seal again.

I wouldn't waste my time and just replace the whole caliper after you check what it looks like!

I have cleaned up rusty pistons and reused the original seals and they were fine, no leaks.
Its amazing how you can look at a piston and see a pile of rust but when its cleaned up it works well.
The problem is usually related to two things, 1. Rusty piston and resultant lack of movement.
2. Corrosion behind the seals which forces them out and increases stiction on the piston.
Combined they prevent the piston from retracting the tiny amount needed to release the brake pads from the disc.

I agree that red rubber grease is essential to the proper maintenance of calipers, When I rebuilt the rears on my Accord they were full of rusty gunge, After removing the seals and boot I heated them with a blowtorch until they were dried out then used a wirebrush to clean the grooves and packed them with Red Rubber grease, then rebuilt them with the original parts.

To remove the piston, pump it out with the pedal as far as it will go, you may need to refill the master cylinder as it can use a lot of fluid.
Its a lot easier than trying to pull them out.


All good now and my economy has significantly increased which I also attribute to lack of brake drag.

shietpilot

CJhaughey wrote: »

I have cleaned up rusty pistons and reused the original seals and they were fine, no leaks.
Its amazing how you can look at a piston and see a pile of rust but when its cleaned up it works well.
The problem is usually related to two things, 1. Rusty piston and resultant lack of movement.
2. Corrosion behind the seals which forces them out and increases stiction on the piston.
Combined they prevent the piston from retracting the tiny amount needed to release the brake pads from the disc.

I agree that red rubber grease is essential to the proper maintenance of calipers, When I rebuilt the rears on my Accord they were full of rusty gunge, After removing the seals and boot I heated them with a blowtorch until they were dried out then used a wirebrush to clean the grooves and packed them with Red Rubber grease, then rebuilt them with the original parts.

To remove the piston, pump it out with the pedal as far as it will go, you may need to refill the master cylinder as it can use a lot of fluid.
Its a lot easier than trying to pull them out.


All good now and my economy has significantly increased which I also attribute to lack of brake drag.

Yeah if the piston surface is relatively smooth after cleaning the rust up it will be fine with a new seal but usually the piston is very rough under the rust and the roughness pretty much destroys the seal to the point where it doesn't retract any longer.

It takes time to rebuild one so it may just be easier getting a new caliper and being done with it. Depends on the extent of the damage of course.

dooroy

You can get a rebuild kit for a lot of calipers now - new piston , new seal and boots etc.
I have got them from the UK a few times but I think they are now advertised on DD in Meath or around that area . You need to have measurements of the old piston to be sure - but your caliper than should be as good as new .

martinr5232

jpbdrogheda wrote:

I'm looking for some tips on how to fix a seized rear brake calliper piston on an 04 Saab 93. Went to change the rear brake pads today and while the passenger side was a doddle to do i ran into a problem on the rear drivers side. I couldn't retract the piston and it seemed seized. I have the correct retractor tool and it worked fine on the other side.

Are you sure your going in the right direction with it one side may be a l/h thread and the other is a r/h.

jpbdrogheda

Thanks all for your replies. Sorry i haven't been about to reply to them all. Lots of good suggestions there. I am having a mechanic friend look at it later this week to see if it can be rescued.

I tried both the LH and RH retraction tool and neither would budge it.

Will update you with mechanics verdict. But thanks for all your replies.

jpbdrogheda

jpbdrogheda wrote: »

Thanks all for your replies. Sorry i haven't been about to reply to them all. Lots of good suggestions there. I am having a mechanic friend look at it later this week to see if it can be rescued.

I tried both the LH and RH retraction tool and neither would budge it.

Will update you with mechanics verdict. But thanks for all your replies.

Spent some time today working on the seized piston. I read somewhere online to open bleed valve a little and turn ignition to ON when retracting the piston. I also spray some brake cleaner around the inside of the rubber boot. I attached a vice grips to the retractor tool and slowly but surely it started to retract

Im not sure which step helped the most but i eventually got the piston all the way in and the new pads fitted. Bled the brakes with the new pads in using the 2-man method. And voila all fixed and working fine.