Installing and Bleeding G50 Clutch Slave Cylinder

[wswilburn]

I am not and expert by any means, but wanted to share what I learned by trial and error.

The slave cylinder is difficult to install with the engine in the car, because it is in an awkward location on top of the transmission, and a spring around the piston makes it difficult to push it onto the studs enough to thread on the nuts. In addition, there is a trick to bleeding the air out.

First an important note. The piston is not self aligning with the release arm. If you do not have it engaging the release arm properly and push the clutch pedal, the piston and other guts will be pushed out of the housing and the part destroyed. Don't ask me how I know this. Especially don't ask me how I managed to do this twice before learning my mistake. Like you, my wife wonders how I can even minimally function in the world, but for entirely different reasons.

The only way I found to ensure the piston is properly engaging the release arm is by feeling with a finger through the observation window of the bell housing. This is a rectangular opening at the top right of the bell housing. Feel the depression in the release arm before trying to install the slave cylinder so you know where it is.

For the next step, you will need both hands at the top of the transmission. If you have difficulty, try dislocating your left elbow. Alternatively, you can borrow a small child from a neighbor, or perhaps on Craigslist. I strongly recommend an unwanted child, as you will likely be returning it in poor condition.

While pushing the cylinder into place with one hand, feel with the other hand to make sure the piston is engaging the release arm properly. Push the piston around as needed. Note that it is possible to install the cylinder upside down. Don't do that. The bleed screw goes on top, and the fluid inlet to the left. Once in place, push the cylinder onto the studs just far enough to start a nut on the top stud. This is the hard part, but it is barely possible. Don't worry about the spring washer, just get a nut on a thread or two. Then tighten the top enough enough that you can get the bottom nut and spring washer on. Fully tighten the bottom nut. Remove the top nut, add a spring washer and replace the top nut. Fully tighten the top nut.

Attach the fluid hose to the cylinder and tighten. Push the hard part of the hose into the clip on the side of the transmission. Installation is complete.

Now to bleed the cylinder. I have found the trick is to raise the car so that the front is higher than the rear by a few inches. This will position the bleed screw at the proper angle for air to come out. remove the rubber cover and attach a hose to the bleed screw, and put the other end into a container for the used fluid.

Put about half a liter of brake fluid into a pressure bleeder and attach it to the brake reservoir. Clamp the overflow hose on the reservoir closed. I use vise grips. Pressurize the pressure bleeder to 10 psi. Using a 7 mm wrench, loosen the bleed screw on the slave cylinder under fluid and air are coming out. Continue until there is no air in the fluid. Depending upon how much fluid you lost in replacing the cylinder, this could take a while. Close the bleed screw and replace the rubber cap. Check the clutch pedal for normal operation. Depressurize the power bleeder and detach from the reservoir. Reinstall the reservoir cap and remove the vise grips from the overflow hose. Bleeding is complete.

A quick note about brake fluid.

In my 40+ years of working on cars, I have become resigned to the fact that anytime I work with brake fluid, I will make an incredible mess. It does not matter how careful I am. I will inevitably forget to clamp the overflow hose, overfill the reservoir, and kick over the used fluid container. I will pull the bleed hose loose from the bleed screw while it is open. There will brake fluid on the car, my tools, and me. It will be on the garage floor, some walls, and if I'm having a particularly bad day, the ceiling. It will puddle under something too heavy to move, and slowly ooze out over the next six months. The only thing to do is have plenty of rags on hand.

After the job is done, the cleanup begins. Five hours later, my trash bin is overflowing with rags and/or paper towels, and there is no brake fluid to be seen. I head into the house for a much needed shower and even more needed beer, tracking brake fluid on my shoes. My wife yells at me, as she should.

In case you are curious, brake fluid tastes bitter and stings the eyes. Fortunately it readily shampoos out of hair.

[rw229]

Nice write up. What were your symptoms leading up to this and did it resolve the issue? I've had two instances where my pedal stayed down, but would work when pulled up. In both cases a bleed fixed it, but I'm thinking some combination of a MC, hose or slave is in my future.

[wswilburn]

The clutch is engaging with the pedal near the floor. replacing the slave cylinder and bleeding didn't fix it. I have since found the roll pin connecting the pedal to the shaft is worn, allowing about an inch of free play at the pedal. This is annoying because I replaced the shaft and pin when rebuilding the pedal cluster three years ago. New pin on order. I'll post the result.

I'd recommend replacing all three.

[wswilburn]

OK I now understand what happened and have fixed it.

When I had the slave cylinder installed improperly, the piston was wedged against the bell housing and could not move. Instead all of that force deformed the hole in the clutch pedal shaft where the clutch pedal is connected via a roll pin. This caused the free play. Replacing the shaft and roll pin fixed it.