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65stanger · Apr 5, 2005

Earlier this year I posted a thread about rebuilding front disc brake calipers. Y'all gave me A LOT of useful info and tips, Thank You....

One of these tips was to use compressed air to "pop" the pistons out of the caliper housings.....worked great, except...........on my four piston calipers only three pistons (of eight total) came out! One each side of one caliper, and one from the other caliper....
Before I took the air gun to the calipers I tapped the pistons (and housings) gently with a hammer, and generously sprayed them with WD40. I also separated the caliper halves.
Here's the question for the brain trust........:
How do I get the remaining pistons out of the caliper housings?
Especially the halves that already have one piston out?

Thanks again for the help........hope more is coming!

65fastback2+2 · Apr 5, 2005

couldnt you hook them up to a brake line with no disc in em and just push the pedal down and push them out?

65stanger · Apr 5, 2005

65fastback2+2 said:
couldnt you hook them up to a brake line with no disc in em and just push the pedal down and push them out?

Theoretically.
Except.......
These calipers were not on my car.
To hook them up so that the brake fluid would push the pistons out, you would need to bleed the entire system.
There are two pistons per "half", on those halves with one piston out brake fluid would just (as the air does now) come out where the piston had been.
The calipers would need to be reassembled, with the old hoses and lines (which were crappy and leaking) being replaced.

To give you a better idea of what I am talking about.......:
This is the calipers before I got the first pistons out, I was only able to get one piston out per caliper before I continued with disassembly.

This shows the partially disassembled calipers, the blue lines indicate the pistons I was able to remove.

limey66 · Apr 5, 2005

How about putting the popped out pistons and seals back in, just enough to make the caliper airtight again, wedge 'em in place with a block of wood (or something) and try and blow the others out. You could then remove the original ones with a bit of a wiggle...the pistons, not yo' ass...

65stanger · Apr 5, 2005

limey66 said:
How about putting the popped out pistons and seals back in, just enough to make the caliper airtight again, wedge 'em in place with a block of wood (or something) and try and blow the others out. You could then remove the original ones with a bit of a wiggle...the pistons, not yo' ass...

Thought of that, when I tried it the block holding in the loose piston was wedging the opposite piston so it wouldn't move either.
That was when i decided to continue on with further disassembling the calipers. I've given the remaining pistons a good soaking with WD40, I was thinking next trying to heat the cast housing?

limey66 · Apr 5, 2005

65stanger said:
Thought of that, when I tried it the block holding in the loose piston was wedging the opposite piston so it wouldn't move either.

OK, how about a 'G' clamp (that's what we call 'em over here, but you guys call a spanner a wrench...) hooked over from behind over the just popped in piston?

65stanger · Apr 5, 2005

limey66 said:
OK, how about a 'G' clamp (that's what we call 'em over here, but you guys call a spanner a wrench...) hooked over from behind over the just popped in piston?

Hmmmmm.....you know limey, you just might of hit on something there....at least it's given me an idea.............

BTW......we call them "C" clamps, but you're right they look more like "G"s.

limey66 · Apr 5, 2005

OK Big Blue, let me know how you get on, I'm going to bed - it's late over here...

65stanger · Apr 5, 2005

limey66 said:
OK Big Blue, let me know how you get on, I'm going to bed - it's late over here...

BRILLIANT limey!
I used the clamp and a block of wood to cover where I'd already removed the pistons, a little air pressure and POP! They came right out, except for two because my wood block started to splinter on the edges and I couldn't get a good seal anymore....
I'll cut a new block tomorrow and get the last two.......

WORD OF WARNING: To anyone else who does this, the pistons can and will shoot out of the caliper, so aim them AWAY from yourself unless you want to dent your head!

bnickel · Apr 5, 2005

65stanger said:
BRILLIANT limey!
I used the clamp and a block of wood to cover where I'd already removed the pistons, a little air pressure and POP! They came right out, except for two because my wood block started to splinter on the edges and I couldn't get a good seal anymore....
I'll cut a new block tomorrow and get the last two.......

WORD OF WARNING: To anyone else who does this, the pistons can and will shoot out of the caliper, so aim them AWAY from yourself unless you want to dent your head!

got a dent to go with this advice Fritz?

limey66 · Apr 6, 2005

Glad it worked.

If you lay a towel* or dust sheet over the caliper when you start to apply the air it should stop the piston shooting through the roof of your garage.

Apparently that's why the MIR spacestation came down a couple of years back...

*Ask your Mum (Mom?) or wife first...

65stanger · Apr 6, 2005

bnickel said:
got a dent to go with this advice Fritz?

Thank GOD, no! But I did almost imbed a piston in the back part of the workbench!

limey66 said:
Glad it worked.

If you lay a towel* or dust sheet over the caliper when you start to apply the air it should stop the piston shooting through the roof of your garage.

Nah, the last couple I just layed face down on the workbench with my hand on the back of the housing steadying it.......

limey66 said:
Apparently that's why the MIR spacestation came down a couple of years back...

*Ask your Mum (Mom?) or wife first...

Ask 'em what, If I can shoot down spacestations?

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