How do I refurbish front nearside caliper?
 

The front nearside brake has stuck on. I have managed to remove the sliding part of the caliper and have the spring and pads to one side.

Around the piston is a large dust seal. How does this come away from the caliper? Do I squeeze in the sides of the dust cover to break its seal and then do I pull it off, is it likely to rip?

I am hoping once the dust cover is removed to be able to get the piston out, clean it and put it back.

In case I need them, can you recommend where to get the piston seal and dust cover from?


stress level is high at the moment due to not having proper access to tools and access to a decent work area


macafee2

There is a video on YouTube that demonstrates a full rebuild on bmw e46 calipers. I cannot access it right now to share a link, but search for e46 caliper rebuild and should find it (they are slightly different calipers, but the principle and layout are the same).

Also search on ebay for the seller brakesint, they sell rebuild kits including the piston (youcan also.look for the exact part numbers via googling budweg brakes, and navigating their site).

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is this the kit you were thinking of?
https://www.ebay.co.uk/itm/FRONT-BRA...4AAOSw-I9dZp0r

macafee2

Having ruined the dust cover I know how it comes off. Within the dust cover against the caliper is a metal ring. Difficult to see the join between seal and caliper with years of crud having built up. Perhaps with a stanley knife blade it may be able to break the seal between dust cover and caliper if you can get it in between where the two meet and prise them apart

macafee2

Hello Ian,

What you're proposing to do is not an easy job by any means. You'll appreciate that the seal between piston and housing will be very tight indeed in order to prevent any leakage of brake fluid. Sorry if I'm asking the obvious but have you definitely established that the piston is the problem?

The weak point with sliding calipers is friction on the pins and/or the external cast iron moving parts. A good session with a wire brush and some suitable lubricant has always been successful for me.

I'd recommend asking an assistant to apply the brakes in a slow and controlled fashion whilst you observe the piston movement and check for any surface corrosion which can usually be cleaned off. If the piston travel is limited, don't overlook the possibility of air bubbles in the brake lines. Otherwise, try repeated manual back and forth movement of the piston.

If, after all this, you conclude that the piston is seized, there are people who specialise in the restoration of brake calipers and that solution would save you a lot of grief.

Simon

Simon, yes I am sure it is the piston. I removed the slider pins and still could not move the piston back. I was beginning to wonder how on earth I was going to remove the caliper it seemed so stuck. I will ask my wife to apply the brakes when she gets home to check again to make sure.

macafee2

When mine did the same, and after rebuilding them a few times, got fed up and just replaced the calipers, both n/side 😎😎

I did this job last year but I was careful not to damage any seals. I opened the bonnet and accessed the brake fluid reservoir to remove the cap and put a piece of polythene close by . Then I made sure that the bleed nipple would release before nipping it up again. I then lifted the calliper away from the disc and once supported, I pumped the pedal to push out the piston , having plenty of rags to soak up the fluid before putting the plastic over the brake fluid reservoir and screwing on the cap the reduce fluid loss. I then cleaned the piston with 800 wet and dry soaked in brake fluid and carefully cleaned the corrosion from just inside the area of the calliper before the internal seal . I then wiped the piston dry and smeared it with red brake grease and then opened the bleed nipple and carefully pushed the piston back in with a G clamp. It might take a few goes as the piston must be square in the hole and can jam if not straight. Once back together, remove the plastic bag or whatever you use from under the filler cap , top up and bleed the calliper. I’ve done this for years as a quick fix if the piston is not pitted. Mine has been perfect for 7 months and about 5000 miles.

Doing the same job but on my daughter's ZS180, both front brakes binding and it's the pistons at fault. Usually I manage to remove the pistons with compressed air (good 12 bar compressor) but these won't budge. Had to tap them out using a cold chisel - one out, one to go. Tea break at the moment. Cleaning with Autosol chrome polish and a rotary cotton pad.
Brakes International are very good, and rather than eBay I'd use their own website. Takes too long to order from UK nowadays so I'm cleaning and hoping for the best.

Regards

Tea break over. Removed the dust cover and seal, cleaned, compressed air, red rubber grease and now I was able to push the piston in by hand, pops out with compressed air. Progress

Not sure if it is the correct one, as they look the same.for.both 190 and standard calipers, but it does look correct.

This is budweg website(who seem.to.supply brakesint, and supply new genuine calipers)

https://budweg.com/

It gives a great breakdown of part numbers and items available.

It.may be worth.considering replacing, as a new caliper if I recall is around 50 pounds

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