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How do I remove pistons from the caliper?


=Enigma=

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Well, I'm at the point now where I'm ready to clean and rebuild my brake calipers. Unfortunately I have already removed them from the car as well as the rear wheel cylinders and I can't get the damn pistons to come out? Is there a trick to doing his when they are off the car?

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Air Pressure. I always use air pressure.

I know, many people don't have air pressure at home. I don't either. I take the calipers to a "friendly" shop in town and use theirs. Blow pressure into the fitting where the bridge tube was connected, but be ready to catch the pistons when they extend out from the caliper.

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Thanks Montoya, I'll give that a try in the morning. I hope I can get enough of a seal on there to get them to pop out. They were working before I removed them and both pads seem to be the same size so I don't think the pistons are seized, just sticky.

Ever seen one of these?

http://www.autobarn.net/lis28600.html

If the air pressure thing doesn't work, perhaps rotating the piston while applying air pressure would help. We'll see.

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my limited experience (I've only done this 3-4 times), is that you don't need a perfect seal (at least with pistons that aren't seized in place) because the volume and pressure of shop air is more than sufficient to rapidly fill (overfill) the caliper bore.

I don't see how rotating the piston (if you can) could hurt.

I've never seen the tool, I just manually push the pistons back into the bore when changing pads. My car has only front discs. Rears are drums.

Let us know how it works for you.

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Ever seen one of these?

http://www.autobarn.net/lis28600.html

If the air pressure thing doesn't work, perhaps rotating the piston while applying air pressure would help. We'll see.

You may need one to reassemble the rear calipers if they are the type with E-brake connections. On those the pistion sort of ratchets out when the ebrake is applied, they need to be screwed back into the caliper, if you just push they will break. I was able to just use a large screwdriver to twist mine back in. Be careful when blowing the piston out, don't get your finger between the piston and caliper body, they come out with a ton of pressure and could cause some real hurt!

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Ever seen one of these?

http://www.autobarn.net/lis28600.html

If the air pressure thing doesn't work, perhaps rotating the piston while applying air pressure would help. We'll see.

I have one of those, or one similar anyway. But those are for rear calipers as LanceM said. For the fronts I just use a blow gun with a rubber tip, apply pressure into the hole where the brake line was removed and the bleed screw closed, and blast it into a rubber pad that I cut just for that purpose.

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Back in my yout', before I had a garage and air tools, I rebuilt the calipers on my Z once. To get the pistons out, I used air pressure - from a hand tire pump! It worked, albeit a little hard to hold everything in place. Had to use one of those cone-shaped adapters that come with sets of ball inflation needles and such.

However, if you use air, DON'T GET YOUR FINGERS IN BETWEEN THE PISTONS! I made that mistake, and when one side let go, it smashed one finger nicely between the pistons. Didn't break anything, but WOW it hurt!

Also seems to me that I had to make sure that they came out pretty equally, since once one is out, you can't get air to help you get the other out.

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Also seems to me that I had to make sure that they came out pretty equally, since once one is out, you can't get air to help you get the other out.

on double piston brakes I use a piece of 2x4, then 1x4 to block them from coming totally out at once and thus ensure both pistons come out, and not just one. Compressed air for me.
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Well I got the pistons out with air from my compressor, but I wish I had read the rest of the posts since last night because I learned a valuable lesson the hard way. The pistons come out of the bore with extreme prejudice! My finger hurts like a son of a bitch. :) Nuff said. Thanks for the help.

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Errr, sorry that I didn't warn you about that. When I learned this trick, I my friend told me to leave the pads & hardware on the caliper (and to keep my fingers out of the way). He said with the pads in place there wasn't much chance of only one piston extending out, & leaving the other still stuck.

I feel bad, and hope that your finger isn't too badly squished. :nervous:

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Yeah, I ended up putting the pads back in so I could get both pistons out. Sounds like I went hrough the normal trials and tribulations of your typical Z newbie. The pistons are fairly clean. Just a few nicks and a little marring but nothing that can't be fixed. Thanks again for the help.

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  • 2 weeks later...

Amen on the crushed finger. I put my hand inside the caliper and applied the air. BANG! I had 2 sore fingers for a week. They turned black and blue. I think a block of wood will work just as well. When they come out, watch out. They fire just like a gun. Yeah baby!

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Pssssttttt . . . . BANG! POP! Owwwwww! Never had it happen to me. I always wrap a rag around the area where the air gun goes into the brake line hole and put one over the pistons as well. Flying brake fluid is definitely not good for your eyes.

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Better be careful with this "bolt into the caliper" trick. I an not certain the threaded hole is not a pipe thread or has a seat built into it. Stick with the air pressure and don't mess with the threads is my advice. (IMHO)

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even if the bolt trick worked (and I'm not too sure it would) that would still leave the piston in the other side of the caliper to deal with.

IMO air is the way to go, just watch where you park your pinkys. :)

On opposing piston brakes it would. I can't remember what the stock 240s are as I don't have them anymore.

As for the thread pitch, its 10mmx1.0 and there are no seals. My home business is powdercoating brakes, and I do 10-30 sets per month, but mostly corvette brakes now.

The point is, there is one seal inside of a brake and it runs the circumference of the pison, right next to the pad. Brakes are really simple, once you've taken them apart.

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This is on the same track as with the front caliper piston removal...

I have a stuck wheel cylinder piston I am trying to rebuild. For the life of me, I cannot pull it out, or even spin it, for that matter.

I tried cleaning it out with B12, then spraying PB on it, let it sit for an hour, tapped on it for about 5 mins, and nothing. I even tried spraying with the airgun into the brake-line fitting threads with 125PSI...nothing.

I filled the area around the piston (where the aluminum housing and piston meet) with PB and let sit overnight...nothing.

What more can I do? Does anyone know where I can find a left side wheel cylinder, new? Not on e-bay very often.

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If the piston is that stuck it probably isn't worth rebuilding.. But if you must, try using a small C clamp and try pushing it in, that may break it loose so it will come out. You should be able to find a new one at NAPA for around $20 or so.

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pre 6/72 production date RWC's are expensive compared to post 6/72 RWC.

As Lance says, if the piston is THAT stuck, the aluminum RWC bore is almost certainly trash.

MSA carries the ones you need, and I'm sure that other places do also, but I've never been able to get one from a NAPA, Autozone, Carquest etc for an "early" 240.

Good Luck in your quest.

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