Rebuilding Rusty Brake Calipers – Black Flagged E30


 I can’t afford a big brake kit for my e30. Not yet anyway. There are too many other upgrades and repairs that have to happen before I can spend the money on a proper set of brakes. 

 

So in the meantime I’ve decided to rebuild my old stock BMW brakes. The previous owner had given me a set of brand new replacement rotors and pads he hadn’t installed, so I already had a head start. All that was left was to take these old rusty calipers and make them look and work like new again. When I say rusty I mean 27 years of nobody even cleaning them. Judging by how hard it was to break the lugs free the first time I took the wheels off, I’m not sure anyone even looked at them since 1991. But here I am, the lucky winner. 

E30 Rusty Brake Calipers

The first thing I did after removing these crusty old calipers from the car was disassemble them in preparation for sandblasting—removing the pistons, seals, etc. Fortunately my brother-in-law has a nice industrial sandblast cabinet in his machine shop just down the road, so it didn’t take much to take off all the years of buildup. As an experiment, I tried cleaning one caliper with a wire wheel and drill before sandblasting, in order to compare the results. What a huge difference the sandblasting made in cleaning these calipers—no contest really.

e30 rusty calipers cleaned up

With calipers this rusty, a little pitting is inevitable

After getting the calipers good and clean with sandblasting, I promptly took them home, plugged all the holes, and sprayed them with primer. Three coats. Then I painted them with black caliper paint. Again, just a spray can. Obviously there were other colors available, but I’m a fan of black. And since these are just stock calipers I didn’t want anything too flashy—no need to bring attention to a standard setup in my opinion. So three coats of black, then three coats of clear. I let them cure for a couple days then got to work on rebuilding them. For stronger, more permanent finish, see if you can find a 2 stage caliper enamel.

Black Flagged E30 rusty calipers

I ordered the appropriate caliper rebuild kits for the front and rear, along with new bleed screws and guide repair kit (front) or guide bushing set (rear) so I can build them to as good as new.

BMW E30 Brake Caliper Rebuild Parts

Everything went together without a hitch. I learned it’s a good idea to put a little brake fluid around the piston and on the new seals when installing them, just to keep everything lubed and moving smoothly. Friction is the enemy. Everything else was pretty straightforward. After rebuilding the calipers I installed new pads and then it was a done deal.  Check out the video above for the details.

Installing new orings and seals bmw e30 calipers

Now I have to wait until I finish the front end rebuild as well as rebuilding the rear before I can install these beauties and test everything out. There’s a lot of work to do, but it’s definitely going to be worth it. 

e30 rusty calipers painted

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2 thoughts on “Rebuilding Rusty Brake Calipers – Black Flagged E30
  1. John Fox

    What about the condition of the piston and the bore of the caliper? did you clean and hone these? I’d expect the piston and bore surface were rusty or scored if the calipers were so old, neglected. Any moisture in the brake fluid will give you corrosion, and the piston dragging a less than perfect surface over the new seal will wear out the seal.

    Curious, did you hone the bore? clean the piston surface? use a new piston?

    • Black Flagged

      Hey John,

      The pistons were actually in good condition, so I didn’t do anything to them. The only part that was a little rough was the exposed portion that goes against the caliper, so I just cleaned that up slightly with a file to make sure it was nice and flat. But I left the inner part of the piston alone since it looked good.

      Does that answer your question?

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