I removed the Girling front calipers from my 1990 740 GLE 16v, and pulled the pistons out (what a chore!) to put rebuild kits in. The pistons do show some wear markings about halfway up, but are not heavily scored or pitted.

However, once I got the seals out and the pistons / bores cleaned up, I put the pistons back in the bores ... and it seems that one of the pistons in particular can be wiggled back and forth slightly in the cylinder. You can't see any movement, but you can hear it as you wiggle the piston. I have to say, sheepishly, that I might have caused some of this play with my brake cylinder hone. It was the first time I had used a hone, and it seemed like such a good idea; it did get the cylinder nice and clean, but I worry that I might have removed some metal also.

I put new seals in, and lubricated the pistons/bores with brake fluid, and put them back together. Things seem to fit pretty well ... too well, in fact, as I am not able to get the pistons to go all the way in without tapping them with a dowel and a hammer.

Question is - if there is play between the piston and bore, can the calipers be reused? Will this freeplay cause binding or leaks? Should I buy new calipers, or put everything back together and see what happens?

I also note that the upper guide pins are very wiggly in their guides, while the lower ones are much tighter. Anything that can be done about this? And, do new calipers come with mounting brackets and guides?

Thanks so much.

RO





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R.O.