Seized brake caliper pistons

canada karl · Post by **canada karl** » Wed Jan 27, 2010 4:52 pm

I've allready got the calipers off the car . (I know ...I should have used the hydraulics to pop them out.)Two pistons are really seized up. Soaked the caliper in solvent for two days. Hard to get a grip on the outer pist

on with a vice grip as well.Anyone have any ideas on how to free them up short of mounting them back on the car, blocking the the other pistons and pressing the pedal down? What about filling the caliper with PB Blaster thru the bleeder valves? I was hoping to be able to free them up and reaseal them now that they are out of the car. Would a brake shop have an alternate method to get them out?

emmodg · Post by **emmodg** » Wed Jan 27, 2010 7:46 pm

I soaked mine in brake fluid for a good while, sprayed some PB Blaster on/in the seam between the frozen piston and caliper orifice. I then put the caliper in a vice, (you have to be "creative" on finding a way to clamp it...), then, and be careful here, I used some vice grips and "pinched" the edge of the stuck piston and started turning the piston back and forth. You have to be careful and mindful of the amount of damage you can do to the piston - DON'T scar/damage the sides of the pistons that go in and out of the caliper orifice! The pistons can take a little damage to the edge that contacts the brake pads but they'll leak like a sieve if you scar the piston sides. The vice-grip method worked like a charm. You may not be able to move them back and forth with the vice grips at first but eventually they'll move more and more until they start coming out. (You can "lift" the piston a little with the vice grips as the piston moves more and more.)

cpalmer · Post by **cpalmer** » Wed Jan 27, 2010 8:08 pm

I would use Marvel Mystery oil.

I found it a few months ago and am like a mad dog with it.

Makes PB blaster look like a vegie oil.

It frees up old frozen pistons in engines, it will work on the ones on your calipers.

It's what I used when I had a caliper re-stick after a brake job in the summer.

Stuff is freaking PRICELESS in my mind....

I would buy a big bottle and pour it all over, or put some in a spray bottle and go from there.

It's 5 bucks. Good luck.

canada karl · Post by **canada karl** » Wed Jan 27, 2010 9:30 pm

Lenny D. · Post by **Lenny D.** » Sat Jan 30, 2010 2:06 pm

I used compressed air the first time I rebuilt mine. Be careful as they will leave the caliper with force when exiting!

Now I just buy remans.

Mike W. · Post by **Mike W.** » Sun Jan 31, 2010 1:11 pm

Compressed air like Lenny said, and make sure your fingers aren't inbetween the pistons when you do apply air. I've never used it on seized ones, but just trying to get leaky ones out can be a challenge. Hit it with air and it comes right out. Remember your fingers though.

thomas_m535i · Post by **thomas_m535i** » Mon Feb 01, 2010 6:04 am

Interesting trick with the compressed air.

I'm also about to refurbish my brake calipers. It looks like the bolt (for keeping the two brake caliper parts together) is NLA. And I'm not quite certain it's reusable. Can one easily replace the pistons and rubbers without splitting the caliper?

Thanks, Thomas

Mike W. · Post by **Mike W.** » Mon Feb 01, 2010 1:51 pm

thomas_m535i wrote:Interesting trick with the compressed air.

I'm also about to refurbish my brake calipers. It looks like the bolt (for keeping the two brake caliper parts together) is NLA. And I'm not quite certain it's reusable. Can one easily replace the pistons and rubbers without splitting the caliper?

Thanks, Thomas

Yes, easily done without splitting the halves. And all the manuals I've seen make a big deal about not seperating them, I think there is a seal in between and I'm not sure it's available. But like I said, no need anyway.

thomas_m535i · Post by **thomas_m535i** » Mon Feb 01, 2010 2:53 pm

Thanks Mike, that's very good news!!

I found out more as well. According to Adam W. the bolts in question are stretch types (http://www.e12m535i.com/BMW_E12/myM535i/M535i_11.html), thus should probably not be reused, and are NLA. Surprisingly, W&N should've the seal and caliper bolts. Although it looks like the bolts will not fit on all E12's: http://www.wallothnesch.com/e/brake/brakee12.htm

So I reckon I will not split the halves

. A good cleaning, a quick bead blast, some heat resistant paint, new piston rubbers, and maybe new pistons should do the job. Let's just hope that those seals in between you mentioned will remain intact...

By the way, also check this write-up from Tony BMW (E12 M535i owner):
http://www.tonybmw.co.uk/pages/project_ ... liper.html

Firstfives.org

Seized brake caliper pistons

Seized brake caliper pistons

Thanks for the responces.n/m