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Join Date: Mar 2006
Location: Cave Creek, AZ
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Stefan and I swapped out the master cylinder on the e39 M5 with the master cylinder from the e65. The cylinder diameter is increased to 27mm from 25.4mm for the front brakes, the rear remains 20.64mm
Remember - Use Caution, brake fluid eats paint!
Access Brake Master Cylinder by removing Cabin Filter
Drain Master Cylinder
Remove Cover Shelf above the brake Booster in engine bay
Loosen pipes from Brake Master Cylinder
Inside the car, release the brake pedal cross pin from the booster and remove the 2 bolts holding the brake booster to the chassis
Use master cylinder as a lever to raise the assembly, then remove the master cylinder from the booster
Installation is reverse of removal
Raise car, remove wheels
Power bleed braking system, we bled the system twice with engine running, starting from RR, LR, RF, LF.
• BMW Master cylinder Part Number 34 33 6 785 926 or 34 33 6 797 650
• M10 to M12 Brake line adapter
• ATE SL6 Brake Fluid
In order to make the e65 master cylinder work there are 2 modifications needed:
· The M10/M12 brake line adapter is used in the driver’s side port shown in photos below. The Brake line on the car is M10, the port on the master cylinder is M12.
· The Mounting flange on the new master cylinder must be modified as shown for reservoir mounting clearance. Some material must be removed from the flange by a cutting wheel in order to for the reservoir to mount.
The braking system responded very well to this modification with more response to the brake pedal that is easily modulated. The calipers on my car are stock BMW M5 brakes with Goodridge SS hoses, ATE SL6 fluid, and EBC red pads on the calipers. My car has over 120k on it, so some of the improvement comes from replacing a 17 year old master cylinder, the remainder of the improvement comes from the increased cylinder diameter of the new master cylinder.
I can email photos if someone else can post for me, I cannot post photos to this site.
Last edited by bdiefAZ; 3rd April 2019 at 09:09 AM.
Reason: Cannot post photos