Went to bleed the brakes on my kart this morning and found that the rubber seal in the master cylinder had swollen to twice its original size. Bit confused as to why this happened as I used the fluid specified when I last bled the brakes. Will I just need to replace the seal and give it a real good flush? Or do I need to go further than that? Chassis is GP Racing and I can’t find any other rubber brake parts online. I’ve also found a small crack in the master cylinder cap, could this have let moisture in and caused it?
Welcome to KP.
Trying to visualize this. Rubber seals can and do swell but double in size sounds unusual. Do you have pics of this? I would suspect the fluid may have caused this. Brake fluid can absorb moisture but I don’t think water is causing the swell but may have caused corrosion in the MC which may cause the seal to appear larger too. If the body of the MC is good then new seals should fix the issue but I wonder about the caliper too.
What fluid is specified?