Hot break master cylinder

[Winks]

Hey everyone, it has been a while. The car was pulled out from her winter slumber, all fluids checked, the battery connected, and she fired right up. After driving a short distance, however, all four breaks began to drag and the problem only got worse. Had the car flat-bedded to my mechanic and he was able to recreate the scenario. One thing that was noticed was the amount of heat coming off of the master cylinder. After cooling the master cylinder off with cool water, the breaks released.

Has anyone seen this scenario in the past? And how have you fixed it? The plan, for now, is to build a heat sheild and see if we can prevent some of the engine heat from making things worse. I may also replace the master.

The car is bone stock and has around 90,000 km

[Timm]

Every time we have seen this it has always been a failure of the master cylinder.

[TxGR8White]

You can use a MC from an E32 V12 - it is a much cheaper option than the E31, and it is basically the same unit. Added bonus: they are readily available, where the E31 MC is not...

[shogun]

The bakelite ring inside the brake master when older starts to getting stuck on the shaft. See my pictures of the internals and how to repair in post # 7 https://www.bimmerforums.com/forum/s...=bakelite+ring

[Winks]

Thank you all for the reply's. I was able to track down the only 850 MC in Canada from BMW and am having it shipped in from BC. Fortunaly my contact at the dealer is giving me a good discount so I can't complain. I will keep you posted if and when the problem is fixed.