Replacing the clutch master cylinder on W201 and other models

This story happened at my home; I pressed the clutch pedal before starting the engine, but instead of usual slight resistance I heard some weird noise and the pedal fell in.

After visual check I found out that the clutch master cylinder rod has broken in the spot where it is attached to the pedal plastic holder.

To disassemble all this we are going to need two spanners and a screwdriver. A 10-mm bent spanner is needed as there’s no other way to get to the cylinder screw-nuts. In theory a ratchet wrench may be used but I doubt it manages to pass through the narrow hole between the car body and the cylinder. Also a 12-mm spanner is needed to unscrew the hydraulic system tubes connection hoses. A small screwdriver for a flat splineway is used to remove the tab washer that holds the rod eyelet.

Remove the plastic cover under the dashboard from the driver’s side and get the rugs out of the way. Use a bent spanner to unscrew the cylinder holder screw-nuts.

Place the 12-mm spanner over the tube and unscrew the clutch master cylinder connection hose.

Before removing the cylinder be sure to pump out of the tank as much brake fluid as possible and place a piece of cloth under the cylinder as the remaining fluid will flow out of it.

Dissemble the tab washer that holds the rod eyelet and dissemble the cylinder by carefully pulling out the connection hose – is can be pulled out easily.

Now, as we’ve got the cylinder, we can perform a visual check.

I found out that the rod is a replaceable spare part so first I decided to replace only it, as the cylinder itself didn’t leak. But after disassembling the cylinder I understood that I have to buy a new one as a set.

It appeared that the pullback spring is completely out of order.

I purchased a new ATE cylinder in a while but to my surprise there was a FTE cylinder in the box.

Mounting the clutch master cylinder
You should begin with the connection hose – detach the tube from the brake fluid tank and pull it inside the passenger compartment. The branch pipe is located to your left if looking toward the windscreen from inside of the vehicle.

Grease the spacer ring with the brake fluid and insert the connection hose into the cylinder. Carefully push the tube into the engine room and insert the cylinder back. Then connect the tube to the tank branch pipe.

Insert the screw-bolts into the mounting holes and put on the cutch master cylinder rod eyelet without tightening it. Tighten the screw-nuts that fix the cylinder, first by hand and then by a spanner. Using the 12-mm spanner tighten the pipe connection hose.

Basically, the cylinder itself it the very upper point of the hydraulic system, so there’s no need in bleeding. Filling the brake fluid tank and pressing the pedal several times would be enough: first you will have to press and pull the pedal but in a while it will start returning to the originalposition by itself.

This method won’t do for bleeding the whole system. You need to bleed it bottom-up by injecting the brake fluid into the cylinder connection hose with a grease gun.

The correct way to do it
You can easily do the bleeding by yourself. Here is what the manufacturer recommends. You are going to need:
1.    A box end wrench.
2.    An about 20-inch pipe to supply the liquid to the windscreen washer.
3.    A metal grease gun with a small metal pipe to supply the lubricant grease to hard-to-get-at places.
4.    Brake fluid.

Do not touch the clutch pedal! Open the brake fluid tank cover. Crack open the connection hose on the brake slave cylinder to make sure it’s not stuck and screw it down.

Fill the grease gun with the brake fluid and attach it to the washer pipe; let the air come out of it.

Put the spanner over the connection hose, insert the pipe connected to the grease gun into it (the air is pumped out and the brake fluid almost drops out of the pipe).

Crack open the connection hose on the brake slave cylinder, take the grease gun and let the brake fluid slowly flow inside. It would be nice if someone could meanwhile watch the brake fluid tank: the fluid should arrive. Or you can check it by yourself by getting to the tank and looking into it from time to time. After you are done, tighten the connection hose and remove the pipe. Done!

Close the tank cover and place back the rugs. Good luck to everyone!

Provided by Kentavr and ZoMer

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1 Response

  1. Gerrit Grundling says:

    Thanks for this. You’ve convinced me that, while I am able to replace the clutch master cylinder on my spacious W123, I’ll rather let somebody else injure themselves on my W202.

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