I put on a new (rebuilt) brake master cylinder and it has a slow leak out of the bottom between the rubber collars and the plastic reservoir. It was hard to get on until I opened the lid on the reservoir. Is it likely that I damaged the rubber collars? I'd pull it off again but this is a big mess.

 

I used a big Tie wrap to hold it down tight, Its working so far

 

Swap this for a new/reman that comes with the reservoir already attached.

 

Unless it leaks to the point of dripping it shouldn't be a problem. I had the same problem after installing the old reservoir on a new master cylinder (what a PITA that was), but it isn't leaking to the point of dripping and doesn't seemed to have affected the performance of the brakes.

 

I'd replace or repair it because it shouldn't be leaking at all, and of all the things that could leak on a car, the brakes are the last thing I'd want leaking besides fuel.

Also, If I were going to go through the trouble of replacing the original master cyl with a different one, i'd want to do it right and install one thats not leaking, seeping, condensating, or what ever else you want to describe it as. It should be bone dry on the outside.

 

For what it's worth, mine is also doing this right now. I had some work done over the summer and my master and slave were replaced, they may have kept the old tank.

I don't see it drip but if I leave the car in the garage for a week or two it'll have some brake fluid on the floor, maybe one drop per day. I've had to top it off a few times to keep the brake light from coming on while I drive it.

I'll try the zip tie idea and see how that works.