Found this on BaT: author unknown. For what it’s worth, I thought I would offer a simple way to restore those old ‘yellowed’ and often hard to find hydraulic Clutch and Brake reservoirs. At least it’s worth a try before spending time and money trying to find a NOS replacement. Of course, no guarantees, but it worked for me. First, drain the brake fluid, remove the ‘Discolored’ reservoir, and clean it/them thoroughly. Next source a bottle of Crème Developer (40 Vol – Peroxide Crème) from your wife’s stash or at your local beauty salon/supplier. Day 1 – Find a large Zip lock bag, add two cups of Developer and place the reservoir(s) in the bag, Zip it closed and swish the developer around ensuring that everything is completely coated. Leave the bag out in the direct sunshine for a complete day (Min 65F, 18C). Day 2 – Open the bag to release any gas and pressure build up. Zip the bag closed, swish again to thoroughly coat the reservoir(s) and leave out in the direct sunlight for a full day. Day 3 – Repeat the process one last time. Day 4 – Remove the reservoir(s), rinse thoroughly in warm, soap & water and blow ‘air’ dry ‘Voila’ – You should have a ‘White’ Reservoir(s). Regards, Alberto
I've tried this and a number of other methods. The plastic always is yellowish when done. Better than dirty but far from new looking.
