Bleeding Clutch Lines

Bleeding brakes usually isn't a problem, as there is (should be) a valve in the bottom of the master cylinder that lets you build up brake pressure, and makes bleeding easier. That's not the valve's purpose, but it is a consequence of it being there.

The clutch however has no such valve. So if you have an air bubble in the line, you put your foot on the pedal and the bubble moves down the line, take your foot off and the bubble moves back again. Makes it really difficult to get the air bubble to the bleed nipple end.

After many years of frustration, I have developed the following method, and it usually takes me about 5 to 10 minutes. Note: this is written for right hand drive cars. Some obvious changes will be needed if you have a left hand drive car. Without really long arms you will not be able to reach both the clutch pedal and the slave cylinder at the same time!

1. Remove the bleed nipple entirely and clean the threads on a wire brush.
2. Fill the master cylinder. Ideally, have an assistant standing by to keep it filled during the process.
3. Remove the driver's side seat base and/or the steering wheel. Not always necessary, but if I don't do this I can't move to step 4.
4. Armed with the bleed nipple and a 7/16 AF spanner, crawl into the footwell.
5. With your right forefinger, block off the bleed hole in the slave cylinder - your finger is now the "bleed nipple".
6. With your left hand, push down the clutch pedal.
7. Take your finger off the slave cylinder, count to 1, put it back.
8. Lift your left hand from the pedal, count to 5, push the pedal down again.
9. Repeat steps 7 and 8 until fluid forces it's way past your finger.
10. Repeat 2 more times, then, with the clutch pedal still depressed, replace the bleed nipple and tighten it. While you are doing this, brake fluid will by running out the slave cylinder as it will be gravity bleeding all by itself.

11. (and thanks to Arthur Harris) Replace steering wheel, or the car is very difficult to steer. I guess we should replace the driver's seat base while we are at it!

"Count to 5" in step 8 is important. When you lift the pedal, you create a partial vacuum in the clutch line. This sucks some brake fluid out of the master cylinder and into the line. But brake fluid is a little viscous, and it takes a few seconds to suck it into the line.

Give it a go and let us know how you get on.

avagoodday
Colin



And here's a comment too...



Hi Colin,

With the invaluable help from your article on bleeding clutch lines I have had great success. Thank you, without your advice I think I would still be at it.

I did add one step however that I would like your comment on. I found it necessary to have the rear of the car lower than the front to make sure the bleed nipple was the highest point of the slave cylinder. This allowed any air in the cylinder to come to the bleed hole otherwise I had air trapped at the piston end of the cylinder which I couldn’t move.

Many thanks again for great advice,

Dave



Good idea Dave

avagoodday

Colin