I mentioned in my last post about flying, Owls Head Maine that the right brake continued having trouble after returning from the mechanics. We have been working on the brakes since then instead of flying.
First, we tried servicing the right master brake cylinder. Tyson took it to his work where they have a full shop. He disassembled, cleaned, inspected, and reassembled, but he did not identify anything in particular wrong with it. We mounted the cylinder back in the airplane and borrowed some equipment from a neighbor to bleed the brakes. The master brake cylinders on older RV-4’s are a pain to bleed because they are mounted upside down. Tyson test flew the airplane, and found the right brake to be no better than before.
So the next step was to entirely replace the master cylinder. My airplane had Cleveland cylinders because that was historically the preferred brand. Now they are rather expensive, so Tyson ordered a pair of slightly less expensive, but still well regarded Grove cylinders. There was even some chance they might fit right side up. We installed them. It turned out the cylinders did not quite fit right side up. My parents helped bleed the brakes. The brakes felt good when we tested in the hangar. Tyson took the airplane out for a test flight and before he had taxied half way down the runway, he reported that the right brake was still no good.
So Tyson spent another afternoon in the cold hangar fiddling with the bottom end of the brakes. The biggest issue he found was that the torque plates and pins were worn and had a lot of play. By wiggling those, he seemed to be able to replicate the brake problem. New parts ordered, wait a week for them to arrive. This Saturday, Tyson replaced one of the brake assemblies, with some emergency help from a neighbor. Unfortunately, we ran out of time to bleed the brakes or test fly the airplane, so we have to wait for next weekend to know if it is fixed for real.