DIY Thread.... http://forums.bimmerforums.com/forum/showpost.php?p=265815&postcount=7

Thanks James

I have a couple of questions.


Any lube other than brake fluid needed?
If you need to do one, should you do all of them?
Any tips on what to cap the brake lines? Just can't think of any household item.
how bad does the piston have to be before you replace it? Any pics of a shot one?

Thanks,
Craig

Any lube other than brake fluid needed?
No.
If you need to do one, should you do all of them?
Yes
Any tips on what to cap the brake lines?
Golf tees will work
how bad does the piston have to be before you replace it?
If there pitting or corrosion on the "wet part" of the piston, replace it. Likewise if there's any pitting of the cylinder bore, replace the caliper.

if its a hose end then a tee like stated or equivalent. If its a banjo end then slip a rubber vacuum hose through the hole

Someone suggested rebuilding them one at a time without disconnecting them from the brake lines. You basically use the pedal to pop the piston out. Anyone done it this way? I'm not liking it because I'm afraid I won't get the calipers as clean as I would if I could take them out and spray them down.

well if your rebuilding the calipers i suspect you are putting new pads in which would meen you either would have to go with new rotors or get the ones you have on cut.

Someone suggested rebuilding them one at a time without disconnecting them from the brake lines. You basically use the pedal to pop the piston out. Anyone done it this way? I'm not liking it because I'm afraid I won't get the rotor's as clean as I would if I could take them out and spray them down.

I assume you mean caliper or piston instead of "rotor's".

I've rebuilt single calipers on the car but if you plan to rebuild all of them anyway then on at a time using the pedal to pop them out is a PITA.

It is critically important that the piston and everything else is clean inside or it will not go back in.

Oops I meant caliper.

I think I'm going to put the car on all fours and pull them all off. I really don't like working bent over in my wheel wells, work bench will be much better.

I assume you mean caliper or piston instead of "rotor's".

I've rebuilt single calipers on the car but if you plan to rebuild all of them anyway then on at a time using the pedal to pop them out is a PITA.

It is critically important that the piston and everything else is clean inside or it will not go back in.

I think you will find it much easier to do with them removed and on the bench. If you have air, the pistons come out very easily.

So I'm half way through. I did the rears first as I figured if I was going to mess any up....I'd rather it not be the fronts. Getting the dust caps on were a little tricky, but I got much quicker on the second one.

When I compressed the first one in, with a 6" clamp, it kind of "popped" in. I hope this was ok...I put some air back in and moved it through it's range and it appeared smooth and stiff.

I used electrical wire nuts on the loose brake lines.

I also tried using caliper grease on the pad backings for the first time, we'll see.

I used the same grease on the guide pins.

Well, tomorrow I'll wrap up the fronts and bleed the system.

Thanks guys for all your input.

I used electrical wire nuts on the loose brake lines.




Careful. Wire nuts have a threaded metal insert inside that could mess up the ends of the lines.

Should work fine as long as you don't put them on too tight.

This is probably the best write up I've seen, too bad the guy kept hitting speedbumps.

http://bmwe32.masscom.net/sean750/caliper/RebuildBrakeCaliper.htm

The piston should go in with little pressure, don't force it. Make sure everything is clean.

Installing the piston a proper brake depressor is best because it keeps the piston square with the bore.

I was going to add that you should get some caliper grease when reinstalling the caliper, but you've already done that.

When I rebuilt the calipers on my Volvo, it was recommended that I put a piece of saran wrap over the resivoir and put the cap back on as a gasket, it would make the lines leak less. Not sure if it helped, I got fluid everywhere.

Also, when you're done and bleeding the brakes, it will be much, much more difficult than a fluid flush, because the air pockets like to get stuck to everything in the system. I'd bleed once/twice, then take it for a short drive carefully (possibly a longer period, say a week, if the pedal is not too bad) and then bleed again.

I was going to add that you should get some caliper grease when reinstalling the caliper, but you've already done that.

When I rebuilt the calipers on my Volvo, it was recommended that I put a piece of saran wrap over the resivoir and put the cap back on as a gasket, it would make the lines leak less. Not sure if it helped, I got fluid everywhere.

Also, when you're done and bleeding the brakes, it will be much, much more difficult than a fluid flush, because the air pockets like to get stuck to everything in the system. I'd bleed once/twice, then take it for a short drive carefully (possibly a longer period, say a week, if the pedal is not too bad) and then bleed again.

I was a bit reserved where to put the caliper grease. I greased the guide pins, but didn't feel confident to put it inside the caliper. Everywhere I read said that brake fluid is good.

Saran wrap is tough on our BMW's with plungers on the caps. I just used some wirenuts to cap the brake lines, next time I'll probably use rubber balloons or golf tees as suggested.

Bleeding.....well that one had me. I would bleed with my motive power bleeder, then just as I'd go to close it up, bubbles would pour out. I'd open it back up...do it again. I started to run low on fluid so I did it as best I could. Went for a test drive...pedal was a bit long and modulatuion was difficult. I've not ever knowingly had air in my lines, but I assume that's the symptom. I will get some more fluid and bleed soon. Track event is on Mon-Tues!!!!

Thanks again guys for your input.

Alright...I've been bleeding this R rear (the first) caliper for two hours on 15psi from a motive bleeder and still getting bubbles...What's up here? How can I get these bubbles out? Should I move on to the other four? Or just wait it out here on the RR?

Sometimes bubbles can come in around the threads of the nipple. I usually use pedal pressure along with my Motive when bleeding to speed the process.

Monitor the fluid used and once you've gone over 1/4 qt (in rear) move on.

Sometimes bubbles can come in around the threads of the nipple. I usually use pedal pressure along with my Motive when bleeding to speed the process.

Monitor the fluid used and once you've gone over 1/4 qt (in rear) move on.

Yes, this can definitely happen and be frustrating. Try to tighten the bleed screw enough that the bubbles stop but not too much that you choke the flow of brake fluid. Also you can try teflon tape (I think. Check to be sure this is brake system compatible)

Sometimes bubbles can come in around the threads of the nipple. I usually use pedal pressure along with my Motive when bleeding to speed the process.

Monitor the fluid used and once you've gone over 1/4 qt (in rear) move on.

Yes, this can definitely happen and be frustrating. Try to tighten the bleed screw enough that the bubbles stop but not too much that you choke the flow of brake fluid. Also you can try teflon tape (I think. Check to be sure this is brake system compatible)

Yes, this can definitely happen and be frustrating. Try to tighten the bleed screw enough that the bubbles stop but not too much that you choke the flow of brake fluid. Also you can try teflon tape (I think. Check to be sure this is brake system compatible)

I think this was the tip I really needed...I was recently shown to open the bleeder screw 1/6th. I think in addition to my caliper rebuild, my next flush is going to involve installing new bleeder valves.

Any input on speed bleeders? They make me a bit nervous, not sure why.