Am in the middle of doing brakes on my 2013 MCS.

I depressed the pedal halfway before removing all 4 calipers and rebuilding them, did not lose much fluid. Rebuilt all 4 calipers after paint them silver with new seals, same pistons.

So I get the brakes back together and bleed them(pressure bleeder) and go for a spin around my building just to test them. First spin around pedal was soft but brakes were still working, albeit probably not 100%. I pulled back into garage and brake fluid had come out of the res cap. So I cleaned it up, bled all 4 corners again. Didn't get much air out.

I go for another spin around the building. Pedal is harder and brakes are working better, but i come back into garage and i brake fluid is coming out of the cap again. Both times I have siphoned fluid out after bleeding to bring down to max line. Tomorrow i will hook up my scan tool and run the ABS bleed service function. Any other thoughts? Do i need to bleed a 3rd time?

 

Never seen that happen, but my guess would be that you got air in the ABS unit and will need to run the ABS bleed function per your plan. I don't know about the Mini but on other cars I've done that on it requires bleeding at each wheel while triggering the pump with the computer.

I haven't tried pressing the pedal to stop flow, but while that might keep fluid in the reservoir it's unclear if it'll keep air from getting into the lines or ABS unit. When I need to remove a caliper I just put an appropriately sized rubber vacuum cap over the end of the brake line, that's enough to keep the fluid in the system.

 

Never tried this test but:
If there is air in the line, remove reservoir fill cap.
foot hard on brakes, quickly off.
Have someone with a towel standing by under the hood.
I had been told when you quickly release the brakes you will see a fluid surge in the reservoir.

never had a cause to test the theory.

 

Update: Ran the ABS bleed function through the scan tool and brakes feel great however fluid still coming out of reservoir cap after running around the building. At this point, I am thinking there is air trapped in my clutch slave from having my calipers off. Clutch was being weird and stalled the car a couple times on test drive, which i rarely if ever do.

I was reading in the bentley manual if you open the hydraulic system that you need to flush and bleed the entire thing so hopefully thats my issues - air in the clutch slave

 

The clutch MC feeds from the brake reservoir, right? So I guess it's possible if you ran the fluid too low you got air in the clutch system. If that heats up and expands maybe it could push fluid out?

Are you sure none of your calipers are dragging, though? If that happened you could overheat the fluid, and that could also cause fluid overflow. Might even explain why you were stalling the car if one or more wheels and the brakes dragging.

 

Bled the clutch slave and now the clutch feels right again, took her for a spin around the building again and driving like normal again but i am still getting fluid coming out of the cap. I bled the brakes again at all 4 corners and ran around the building again and same thing. Brakes and clutch feel like they are operating normally, pedal travel and resistance on both feels correct. But i am getting brake fluid coming out of the reservoir cap after a very short drive around my building. How do i diagnose a bad reservoir cap? Could that possibly be my problem or do i somehow still have air in the system after bleeding 4 times?

 

Might sound like a dumb question, but you're not overfilling the reservoir, are you? There is an arrow on the side. Fluid should be just up to the lower point of that arrow.

Also, check the cap seal isn't getting buggered when reinstalling.

 

Yeah I’ve triple checked I’m not over the max level for fluid. Also I have looked at the cap as close as I can and the seal seems fine, I can’t take it out and it seems firmly in the cap. I tried to get closer to the min line and it seems maybe the amount that leaked went down a little bit.

 

So i brought the fluid level down even closer to the minimum line, about 1mm away from Min and the reservoir did not leak after driving around the building. Time to drive a little farther and make sure everything is still working properly.