Rusty brake callipers

Drew20

Drew20

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I've had a set of four callipers knocking about in my garage for many years. Think they're from an E12 based E24, so have the same 4 pot front/ 2 pot rear set up as on our E9s. Not sure if they interchange, but that's not the point for now!
Thought I'd rebuild them....
So I got all the bleed nipples free, which was a good result. Some plusgas, a few whacks with a hammer and all 8 of them came out without a fight

The calliper pistons are going to be more of an issue though. One is moving freely after a blast of compressed air, but the other 11 look fairly jammed in place. My compressor goes to 7 bar, which is just over 100psi. So not that much really, and not enough to blast them out.
I've read avout using grease guns, or a diesel injector pump tester (whatever that might be). Looking for tips...

I tried soaking a piston in plusgas (so removing the dust seal and filling the channel between the piston and the calliper body) but no joy yet.
 
Funny,

I just got one apart yesterday with the same problem I had the caliper half soaking in a combo of ATF and acetone for a few days Air got all out except for one I had to use some soft wood against the caliper half inside to seal it off ( I had all ready split them ) and then have the good piston also blocked by a piece of wood so it sits at about half way in the bore ( easier to get out later ) Put a grease fitting in the bleeder hole and just start pumping the seized piston just pushed out nice and smooth Now the crappy part, cleaning the grease out of everywhere Next step is to media blast them all, then I will powder coat all the individual pieces


So use the grease it will work
 
The e12 has a slightly larger brake pad and although mount spacing is the same as are the pistons, they sit slightly off center to the rotor. People do use them but you need to compare to your e9 calipers. I have a set of both.
 
Was hoping to avoid hooking them up to my E9, as I've only just flushed and bled the system. But yes, this is a good option, lots of psi going spare! Actually think I do have some old MCs somewhere, not sure about metal brake line, but can diy flare one well enough, maybe...
Don't have a grease gun
 
I filled a grease gun with brake fluid and it worked fine, but the pistons were not so stuck.. Didn’t try air hydraulic is more controllable.
 
I cut off the schrader piece from a bike inner tube, press it tightly into the caliper and hit it with 100psi and boom out they come, put a thin piece of wood in the middle of the caliper to keep it in place but not so much that you lose pressure in the other bore, this will allow both to pop out enough to grab and twist out. No mess.
 
Air pressure did the trick for me as well. Used a slab of wood in between the pistons and out they came. If you dont use the wood, then one piston will come out entirely, releasing the pressure and they other one will remain stuck.
 
I've got five of the 12 pistons free so far. After a tough day in the "office", this counts as therapy... of a sort
:)
One of the pistons in a rear calliper is seized and also fully retracted so I can't even wiggle it. Think I'll need a grease gun for that. The ones I got out have succumbed to heavy duty wiggling with a crowbar. Once they move even slightly, it's only a matter of time
 
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