Boxerworks.com

84 R100

So I'm trying to install the calipers. They bled easy enough, but the left caliper leaks at the seam between the bleeder and the inlet pipe. That's where the O ring sits between the two halves of the caliper. I'm on my fourth attempt. It leaks when I apply break pressure. Parts are clean and dry, I've tried another new O ring and each time it leaks when I apply pressure. I'm tightening the parts at 22ft/pds and I've tried to snug it up a bit more. Can't understand why this is being a problem. the right side is fine.

So is it possible that some brake fluid is residual between the two sides, and when pressure is applied a little bit just reveals itself? It's barely visible. Brakes bled easily and lever is firm. The real disappointment is that after all this work, expense, hassle, the wheel doesn't spin much better than it did before with the brakes un-applied.

I would have thought that you would have cleaned up the facing halves to eliminate that from the equation.

I read it last night, but had no real solution. You had tried multiple o-rings.
Perhaps something slightly larger?

I had no problem at all when I split my caliper halves but the manufacturers and some guru's will tell you they are designed never to be split because of the possibility that they will warp. Even then surely a slightly thicker O ring will do it.

barryh wrote: ↑Thu Jul 06, 2017 3:21 pm I had no problem at all when I split my caliper halves but the manufacturers and some guru's will tell you they are designed never to be split because of the possibility that they will warp. Even then surely a slightly thicker O ring will do it.

The kit to rebuild the caliper comes with a new O ring and bolts from BMW.

Rob wrote: ↑Thu Jul 06, 2017 2:39 pm I would have thought that you would have cleaned up the facing halves to eliminate that from the equation.

I read it last night, but had no real solution. You had tried multiple o-rings.
Perhaps something slightly larger?

I had things very clean and dry but some must have liquid got between. This morning I tried it and there is no leak. What's the lesson????

When I did mine I was worried about that o-ring moving whilst approximating the caliper halves. I put a light smear of grease onto the o-ring, and set that half onto the bench, then lowered the other half onto it. If yours has stopped leaking now, maybe the torques have settled a bit or the seal has settled into place better?

The caliper seam is dry. I'm thinking a bit of brake fluid off the brake line, by capillary action, got into the seam. My problem is now, after all this, I still have drag on the brakes when not applied. If I push the pads back, the wheel spins. I'm wondering if there is a problem with the master. All components of the braking system that I have serviced were spotless. Probably because I am the original owner and flush my brakes min every two years.

My 81 front calipers have never backed off completely. Even with recent new pistons and seals. The rubber seal around the piston is what's supposed to pull the piston back.
I've also not had issues with pad or disc wear.

ME 109 wrote: ↑Fri Jul 07, 2017 4:59 pm My 81 front calipers have never backed off completely. Even with recent new pistons and seals. The rubber seal around the piston is what's supposed to pull the piston back.
I've also not had issues with pad or disc wear.

What a drag. I guess the brakes are working OK. I thought I had a problem with the pads rubbing on the discs. Saw some posts of wheels spinning freely. I guess that was BS that caused me a lot of work and money. Sometimes you're the nail.