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DIY: Do It Yourself
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Old 01-27-2016, 10:07 AM   #1
smcutter
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Help Needed: Brake Caliper Rebuild

Hey guys, I've searched thoroughly but cannot find any tips that will help me out. I'm rebuilding my front right caliper on my 2005 M3. I got all of the parts and tools that I need, but I'm stuck at the point where I need to remove the piston from the caliper.

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I used a pretty strong air compressor to get the piston out this far, but I cannot get it out any farther. Any tips would be greatly appreciated! I'm hoping this doesn't mean the caliper is really knackered and beyond rebuilding.
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Old 01-27-2016, 10:55 AM   #2
smcutter
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I found some DIYs that are not specific to BMWs. I'll give it a shot using the grease gun method and see if that works.
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Old 01-27-2016, 02:38 PM   #3
Gus-CO
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put a little piece of wood in front of the piston, take your hand away and inject compressed air where the brake line connects to caliper... it will spit the piston out, sometimes with quite a bit of speed, that's what the piece of wood is there for, to protect the piston from hitting the caliper on the other side...

Personally I like to get the piston almost all the way out while still connected to the brake line... pump your brake pedal slowly and observe the piston, you'll be able to tell when it starts to rock side-to-side a lot, that's almost out..... If it gets out while connected, no big deal, just have a pan under it to collect the brake fluid.

Last edited by Gus-CO; 01-27-2016 at 02:38 PM.
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Old 01-27-2016, 04:16 PM   #4
smcutter
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Originally Posted by Gus-CO View Post
put a little piece of wood in front of the piston, take your hand away and inject compressed air where the brake line connects to caliper... it will spit the piston out, sometimes with quite a bit of speed, that's what the piece of wood is there for, to protect the piston from hitting the caliper on the other side...

Personally I like to get the piston almost all the way out while still connected to the brake line... pump your brake pedal slowly and observe the piston, you'll be able to tell when it starts to rock side-to-side a lot, that's almost out..... If it gets out while connected, no big deal, just have a pan under it to collect the brake fluid.
Thanks for responding! As I noted below (under the picture, which is probably why you didn't see it) I used a pretty heavy duty air compressor and it's not doing the trick. When I get home from work I'm going to try using a grease gun to fill the caliper with grease and force the piston out. If that doesn't work, I'll try hooking it back up to the brake line and using the braking system's pressure to get it out as you suggested.
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Old 01-27-2016, 04:30 PM   #5
Gus-CO
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hahah I thought it was your signature and totally ignored it! Sorry..

Just a heads up, you probably have done it, but..... Plug the brake line somehow after you take the caliper out. You don't want fluid running out and emptying the whole brake system... It will be a pain to bleed it if that happens! It doesn't happen to every car, but better play safe.
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Old 01-27-2016, 05:22 PM   #6
smcutter
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Originally Posted by Gus-CO View Post
Just a heads up, you probably have done it, but..... Plug the brake line somehow after you take the caliper out. You don't want fluid running out and emptying the whole brake system... It will be a pain to bleed it if that happens! It doesn't happen to every car, but better play safe.
Yeah, I didn't play it safe. I thought I had plugged it well enough, but I got home yesterday and discovered about a pint of brake fluid in the catch pan I put down. Looks like I'm going to have to flush the whole brake system. I'll chalk it up to a learning experience.
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Old 01-27-2016, 09:26 PM   #7
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I tried all methods, and none of them were successful. I'll be ordering a rebuilt caliper tomorrow morning.
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Old 01-28-2016, 08:49 AM   #8
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Originally Posted by smcutter View Post
I tried all methods, and none of them were successful. I'll be ordering a rebuilt caliper tomorrow morning.

The probably the smartest way. I rebuilt a pair of calipers once. They were from an Austin Healey Sprite. What a pain!
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Old 01-28-2016, 10:47 AM   #9
smcutter
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Would you say it's necessary to replace both front calipers? What about pads? The pads were brand new when I bought the car 4,000 miles ago.
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Old 01-28-2016, 02:00 PM   #10
BKMrSteel
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Quote:
Originally Posted by Gus-CO View Post
put a little piece of wood in front of the piston, take your hand away and inject compressed air where the brake line connects to caliper... it will spit the piston out, sometimes with quite a bit of speed, that's what the piece of wood is there for, to protect the piston from hitting the caliper on the other side...
This is the best way I know of. Make sure you really seal the air to the hole. When it pops, it WILL pop with a lot of force! Do NOT have any fingers in the way!

It almost looks like you could just pull it out. Will it not rock side to side yet?
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Old 01-28-2016, 02:37 PM   #11
smcutter
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Originally Posted by BKMrSteel View Post

It almost looks like you could just pull it out. Will it not rock side to side yet?

It's jammed so tightly that even the car's brake system didn't generate enough PSI to eject the piston. I'm gonna call it busted.
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Old 01-28-2016, 03:08 PM   #12
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It's jammed so tightly that even the car's brake system didn't generate enough PSI to eject the piston. I'm gonna call it busted.
Did it tilt? Maybe I missed that information. You may want a new one if it scored the inside. That is to bad though.
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Old 01-28-2016, 03:19 PM   #13
smcutter
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Originally Posted by BKMrSteel View Post
Did it tilt? Maybe I missed that information. You may want a new one if it scored the inside. That is to bad though.
The notch on the outside of the piston is pretty badly scarred and I question its ability to hold a good seal. Combining that with the fact that nothing I've done can get the piston out, I just ordered a rebuilt brake caliper. At least I can do the installation myself.

In other news... does anyone need to buy a caliper rebuild kit for cheap? $10, perhaps? They go for $25ish online.
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