Bleeding the Clutch: Here is a tip

[Dr. Ian McArthur]

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Here is a neat way to bleed the clutch. I spent two days trying to bleed
mine (in an 88 Olympic Edition 5TQ) before I discovered this trick.

You need to "pressure bleed" the clutch because of the vibration loops in
the clutch pipe. These loops keep air bubbles in them as you try to bleed
the system the "normal" way. The solution is to bleed the system "backwards"
from the slave cylinder to the master cylinder to the reservoir.
Fortunately, every Audi comes with a built-in pressure bleeder: the brakes!

Here's how:

1. Hook one end of a neoprene hose to the BRAKE bleed screw on the left
front disk brake caliper.

2. Hook the other end to the bleed screw on the CLUTCH slave cylinder.

3. Open the bleed screw on the clutch slave cylinder and leave it open.

4. Open the bleed screw on the brake caliper.

5. Slowly (so as not to blow the hose off the bleed screws) press the brake
pedal to the floor to pump brake fluid backwards through the clutch system.

6. With the brake pedal depressed, tighten the bleed screw on the brake
caliper (This obviously requires two people). You don't need to close the
bleed screw on the clutch slave cylinder (as long as the hose is a tight
fit).

7. Let the brake pedal up, reopen the bleed screw.

8. Repeat as necessary to fill, one pump at a time, the entire clutch system
with brake fluid.

There are a couple of nice things about this trick. For example, as you
gradually fill the clutch slave cylinder and pipe, the air bleeds off
through the clutch master cylinder into the brake fluid reservoir. Sitting
in the car you can just see the reservoir through the gap under the open
hood and watch the bubbles as you depress the brake pedal for each stroke. I
keep the reservoir really full, right to the top, so I can see the bubbles.

As you progress you have to keep filling the reservoir. Finally, you will
get all of the air out of the system and as you depress the pedal, no
bubbles will be seen. To be really sure, I always pump quite a few extra
cycles. The brake fluid will not over flow the reservoir, as you are just
cycling it through from the brakes to the clutch.

Another neat thing is you can see how dirty and discoloured the fluid in the
brake system is. Mine was so dirty that when I was through I opened the
bleed screw on the clutch slave cylinder and let the dirty fluid drip out. I
watched carefully and kept filling the reservoir until I figured I had
replaced all of the old fluid. Then I bled the brake (a lot!!) to replace
the fluid in the brake system.

Give it a try. Please let me know if it worked for you.









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Dr. Ian McArthur, Consulting by Acronym, Cochrane, Alberta
ian at sutul.org

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