R55 / R56 MCS Clutch Bleeding Instructions
(passing along my my notes. hope they help)
Here is how to prime the clutch. The whole process should take under 20 minutes.
This is how the system works - The clutch operates using brake fluid. It draws off the brake fluid reservoir via a black tube on the side. Fluid flows from the reservoir into the cylinder above the clutch pedal (when there is a negative pressure). Then when the pedal is pushed the pedal cylinder pushes fluid through the tube into the clutch slave cylinder which activates the clutch. The clutch slave cylinder is attached to the tranmission on the front, lower, left side. It is a black plastic cylinder that has the bleed valve. Look under the driver side head light a little inboard. When there is air in the system simply pumping the clutch does not prime the system. It just moves a little fluid back and forth. And pumping until your arm falls off will not do anything.
Step (1) Attach a clear 3-foot tube to the bleed valve. Keep the tube elevated to keep air out. Place other end in a plastic bottle to catch fluid. Note: The clutch slave cylinder is after the bleed valve and therefore difficult to remove air. The method described here will allow you to push fluid into the clutch slave cylinder.
Step (2) Pull the pedal up, open bleed screw, push pedal to the floor, tighten bleed screw. Then very slowly pull clutch pedal up. This allows the fluid to flow into the petal from the brake fluid reservoir. Repeat the process (up, open, floor, close, pull up slowly). You should see a mixture of air and fluid flowing into the tube. Keep repeating (5-10 times) until the fluid flowing in the tube is void of bubbles. Note: Make sure that the brake fluid in the reservoir remains above the clutch passage.
Step (3) With the bleed valve off you should start to feel resistance when you pump the clutch pedal. If the pedal is soft you have air in the clutch slave cylinder (or a leak in the system noted by a brake fluid puddle).
Step (4) Prime the clutch slave cylinder. Make sure the clear 3-foot tube that is attached to the to the bleed valve is still filled with fluid. Empty out the last 4" from the end. Clean the end with a lint free towel and soap and water. (be careful not to get anything into the tube).
Step (5) Blow into the tube (or attach a small pump) to push fluid back into clutch slave cylinder. Try to push at least 2 feet of fluid back into the system. But stop before emptying the tube. Then close the bleed screw. (be very careful not to get any fluid into your mouth)
Step (6) With the bleed valve off pump the clutch pedal. You should feel close to normal resistance at the top of the pedal.
Step (7) Clear any air that you pushed out of the slave cylinder by repeating Step (2) a couple of times (up, open, floor, close, pull up slowly). Stop when you have pushed out more fluid than you blew back in.
Step (8) With the bleed valve off pump the clutch pedal. You should feel normal resistance at the top of the pedal. If not you may need to repeat the process. This works for me the first time.
Written By: Ken Suzuki
Article Date: Mar 29, 2011