This topic relates to my 1996/7 Mini, more specifically to the brake master cylinder (MC) as shown in the photo. Some time ago I refurbished this with a new seal kit GRK1032. All worked fine until suddenly this week it didn't any longer: all brake fluid had leaked out from the reservoir. I then verified that the slave cylinders (rear) and calipers (front) were not leaking, and that all the brake hoses and connections were dry. Which was the case, so the problem was limited to this MC. I topped up the reservoir with fresh brake fluid to see what would happen. The next day all fluid was on the floor, and I could clearly see where it had leaked. The reservoir has two points where it feeds into the MC. Each of them has a black seal, as visible in the photo. The one on the left hand side in the photo (near the ap logo) is leaking; the other one is dry. Also: after removing the MC from the car I could confirm that the MC itself is not leaking: all is dry at the piston, and there is no fluid in the brake booster (servo).
Looking back into my notes I made when I refurbished this MC I notice that I had great difficulty in installing the reservoir on top of the MC. There is/was a fitment issue with the two seals at that location. If I placed the seal over the reservoir tube was I not able to push it into the MC. If I placed the seal in the MC was I not able to push the reservoir on top of it. The seals' wall are slightly too thick to fit properly. So I used a sharp knife to remove a little bit of material to make it fit. It could be that this improvisation is now the root cause of the leakage. I didn't notice it at the time, but now notice that the reservoir can easily be wiggled from left to right. It doesn't seem to be mounted very solidly on the MC.
My questions are:
1. Have others had the same fitment problem with these seals between the reservoir and the MC?
2. What solutions are available to have it properly fitting, and still being able to assemble it?
3. Any other recommendations or tips related to this topic?
Attached Files
Edited by NLinPEN, Today, 11:43 AM.












