I thought I would do a write up on rebuilding my brake callipers as I found out that one had seized when I tried to change the brake pads. My car is a E36 328i with M3 evo calipers but this should work for any BMW single piston caliper.
So, this sounds quite daunting but is actually really easy. Your going to need a few things, there is nothing like having the right tool for the job.
1. 7mm Allen wrench socket
2. Torque wrench
3. 13mm spanner
4. 6mm spanner
5. A G-clamp
6. A tray for catching the fluid
7. A box for keeping the bits your taking off safe
8. 500ml of brake fluid
9. A caliper rebuild kit (about £36 each side with replacement piston or £15 without, mine was with)
10. Cheesy bacon roll.
OK, first thing to do is remove the caliper off the hub, youíll need the 7 Allen socket for this. Remove the dust caps and undo/remove slider bolts.
Some guides will advise to hook the caliper onto the strut with wire but I found it best to have a box sitting high enough to rest the caliper on. Remove the pads; if youíre keeping the same pads, put in a box or tray with the slider bolts and anti rattle clip for later.
I should also say at this point the Iím only doing one caliper at a time, the reason for this will become apparent in this next bit.
Next thing to do is put the caliper in a tub or tray and pump the brake peddle. This will push the piston out until you can remove it by hand (the other caliper will just press against the disc). Just pump the peddle a couple of times then go round and check to see how far it has moved, you donít want to pump out any more brake fluid than you need to. It should then look like this:
Now to undo the brake line. I have to admit that I was not particularly gentle with the lines but mine are braided and can probably take a bit more punishment (no excuse). Just be careful if you have the standard ones.
Check the rust out here, if yours is like this you know that this is going to be worthwhile.
I found this little rubber cap that came off the HSD top mount thread for protection, it was perfect for stopping the brake line dripping all over the place. Maybe a valve cap would do the same job.
OK, so if you have got this far your caliper should be free and clear and in a pool of itís own fluid. Lucky calliper!
This is my refurb kit, it comes with all rubber seals and a new piston.
Itís time now to remove all the rubber part from the caliper , itís really simple but hereís a few pics anyway.
Now time to give the inside or the block a clean and inspection. Scrap away any areas with any corrosion, pay particular attention to the groves where the seals fit. If there is corrosion inside past the inner seal you might be looking at a new caliper altogether. Remember people, these are one of the most important parts of your car, donít go cheap on them.
Still here? Good. Time to put the new seals and rubber part on fairly self explanatory. For the slider boots just pull then thru with some thin nosed pliers, and I will say this; its much easier to do it this wayÖ
Öthan this way.
The inner seal is really easy to fit, use plenty of the silicon greaseÖ
The piston dust guard is slightly trickierÖ but there is a knack to it. Iíll try and explain but youíll really only know what I mean when you try.
Place the guard over the piston, the inner seal that fits on to the piston is at the opposite end and the outer seal is sticking out over the top like soÖ
And again, plenty of silicon grease over the whole thing. Now place the piston in position and line up the outer seal at the bottom, this will actually align itself which is handy. Now you want to push the seal in all the way around, hold it with your fingers at either side and leave enough of a gap between the piston and the caliper just to tuck it in. Once you have tucked it in push the piston in slightly and youíll feel that the seal has aligned all the way around. You can now push the piston in as far as you can.
I will most likely be quite hard to push it by hand so I put the old pad back on and used the clamp to gently press it back in. You will need to push it right back so the dust boot folds in on itself if you are fitting brand new pads due to the thickness.
Fit your new pads and reattach the brake line. Itís important that you do this before reattaching the caliper to the hub as the brake line wonít twist. Also depending on which side you are doing, remember to clip the pad wear sensor back in too, then bolt the slider bolts back in. Bleed the brake by loosening the bleed nipple attaching a short hose into a carton and pump the peddle until the fluid comes out and re-tighten. Donít forget the dust caps too and youíll need to top up the brake fluid.
Now stand back and feel very proud of yourself. And have that cheesy bacon roll.
I did both sides on mine coz Iím OCD like that. Check the difference between the two. The rusty one was the troublesome one and you can really see why
Well I hope this helps (and works too as I havenít tested it yet :O)
As usual, this is that way I have done it, I accept no responsibility for you injuring yourself or damaging you car yada yada yadaÖ..