22 replies to this topic

[minimissionary]

I thought they might be "once only" bolts, but considering the other one is untouched, I'll take the risk and tighten the buggery out of it and use loctite.
Can I use spray on 'Gunk' to clean the caliper inside and out? Looks like water has leaked in and stained the bore, but it's not rusted or anything, just dirty as hell. Will be wire brushing the outside to make them shiny.
One last thing; is there a certain way up for the seal and dust boot to go in? They look the same either way up, but I'm sure I read somewhere theres a right (and wrong) way up.

[dklawson]

With the brake calipers on the Mini (and most other cars) it is not rusting of the caliper bore that is necessarily a problem but rust in/on...
1) The glands/grooves where the seals sit in the calipers, and
2) The outer cylindrical surface of the pistons.

The bore of the brake caliper does nothing more than guide the piston. Remove rust there to prevent binding and to remove contamination in general. While cleaning the bores, look very carefully at the grooves where the seals sit. Make sure they are clean and that any rust in them is removed. You have new pistons now so their outer diameter should be pristine. Pits on the OD of brake pistons (like your old ones) are only really OK to use if the pitting is WAY out on the tip of the piston and not in an area where the pits will be working their way over the rubber seals.

The dust seal on the larger brakes must be different than on the 7.5" calipers that I am used to. On the 7.5" calipers the dust seal can go in either way but the metal keeper that holds it in place is "L" shaped and must go into the groove with the foot of the "L" pointing out to hold the dust seal in place. There have been some threads over the past year discussing how best to seat that metal retainer. It can be a pain if you don't have a tool or something to improvise with.

Since your calipers will be almost completely apart, clean away with your Gunk. However, after the gunk be sure to use regular soap and water to remove any petroleum residue before you fit the seals. Brake rubber does not like petroleum. Also, wire brushing will not make them shiny but it will remove loose rust and dirt. Clean the calipers up as clean as you can (inside and out), blow the calipers dry with compressed air (inside and out), then consider masking the caliper bores and tapped holes and spraying them with brake caliper paint. Above all else, keep everything clean and make sure you have washed out all the petroleum from the Gunk.

[Cooperman]

Best to strip the two calliper parts and clean with 'Brake & Clutch Cleaner' very, very thoroughly. There must be absolutely no DGS anywhere inside the brake fluid areas.
Then when re-assembling use rubber-grease and clean brake fluid.
The old bolts holding the two halves together can be re-used, but torque them to 45 lb. ft, not just very tight, and use some Loctite on the threads.
Fitting the dust shields can be very difficult, so do it slowly and with care.

[minimissionary]

The 'L' pointing out? So the seal sits in the foot of the 'L'? In which case, whoever did these last completely mucked it up!

[Cooperman]

Of course, the 'L' points inwards. If it didn't the seal could just fall out!

[minimissionary]

Got quite confused there Think I'll buy some brake cleaner tomorrow. Might as well do it by the book.

[minimissionary]

I've started cleaning them with a brillo pad to get any crud off without scoring anything badly enough to prevent it sealing properly. Will the detergent react badly with anything? I've got some brake cleaner to use afterwards to remove any last bits of grease.

[dklawson]

The Brillo will be fine. When you are done, use an old toothbrush or similar to clean inside the caliper bores and sealing glands in the bore. Rinse thoroughly with water and scrub again with the toothbrush, then blow dry. Finally flush the surfaces with your brake cleaner and blow that dry.