I installed a new brake master cylinder 2 months ago and now it is leaking from the cap, I think. I also changed the proportioning valve with a new one from the dealer, and I also did a new booster.

The new master cylinder had been sitting in my basement for the past 5 years, as I took a long time to get to this fix.

The brakes feel great. I have a smooth brake pedal with range and good incremental stopping power. But now I am leaking brake fluid. Any suggestions? Thanks.

 

I would suggest the neoprene seal in the cap has dried out and has a crack in it. There is a squirt of brake fluid every time you hit the pedal before the pistons seal off the relief ports that can be forceful and hit the top of the reservoir. A small crack can allow some fluid to leak out then. Problem is, I have no idea where to get a new seal. I'm surprised the piston seals are still good after sitting for 5 years!

 

Thanks, Dave. I try the old cap from the old reservoir and see what happens.

 

I do know if you don't remove the cap when pushing in the calipers, it will push out.