Brake Fluid Leak and a Caliper Headache

April 30, 2025 • Sivert • 6 views • 1 min read

I noticed a strange puddle under the car, and it was not petrol or oil. It was brake fluid. One of the rear calipers was leaking, and not by a little. GTI calipers are expensive, so I tried a rebuild kit first.

Disassembly took some figuring out. The Edition 35 calipers are not like others I have worked on. The retaining ring design made no sense to us, so we ended up whacking the back of the caliper with a hammer, on the theory that there was no retaining ring at all and this was a fine way to get it apart. Then we worked out that all we had to do was twist the brass ring out.

Retaining ring setup unique to Edition 35 — As you can see, there's an edge the bronze retainer hooks onto. All we had to do was twist it clockwise to loosen it.

We got the piston out and replaced the seals, and that is when the real culprit turned up: a rust path behind the seal.

Time was tight, because I had a big group drive the next day. So off to the auto parts store to buy a new caliper. Crisis (barely) averted.