Bleeding the clutch

[waltklatt]

It's getting a bit frustrating to bleed the clutch.
I've rigged up a bicycle tire pump to a jug half filled with brake fluid and a long line to the clutch slave bleed screw.  
Using the pump I am pressurising the jug and the fluid is being forced into the system and filling up the clutch fluid reservior on the brake booster.  There are air bubbles present in the reservior.
I have now bled the system 5 times and it still doesn't give me a good pedal feel.  The clutch is still partially engaged at all times.
What is the proper proceedure to bleed the clutch.  I know the other method using the left front brake caliper to bleed into the clutch.
Do you leave the pedal to the floor?  Do you back the slave out a bit?
Clutchless,
Walter
1967 220SL-diesel

[JimVillers]

Walter .... Bleeding the clutch was also one of my most frustrating jobs.  As I recall, I ended up with a pressure bleed from the reservoir.  Then I just worked it until it worked "good enough".  Job 29-5 in the early manual covers the pressure bleeding procedures.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[waqas]

Walter,
I was similarly frustrated with other methods, until I finally followed Joe Alexander's advice in an old post somewhere here regarding using the brakes. It really was a breeze doing it this way!  In fact, I found out later that the BBB (1968-onward) also recommends this procedure as an alternative.  I used the right caliper (not sure why the BBB recommended the right and not the left), and once I got clear fluid up in the clutch reservoir, sans bubbles, I tightened the clutch slave bleeder (I never loosened the master cylinder's bleeder). The pedal became tight again. Then I bled the front brakes as usual. If you want more details, just ask!

WAQAS in Austin, Texas

[ja17]

Hello Walter,

Yes as Jim has mentioned this can be most frustrating. Sometimes this sudden activity  to this hydraulic system, will cause a weak link to fail, like seals in the master cylinder. a restricted clutch hose makes bleeding the system more difficult.

However try some of these procedures:

The pedal must be all the way up so the fluid and air can escape to the reservoir. Some other methods that may work are about a hundred full strokes of the pedal allow to rest after each twenty. Eventually the pedal begins to react. After it begins to respond it will purge itself fairly soon. Another fix is removing the slave cylinder (while still connected) and compress its piston. This will force traped air out of the system.  After re installation the pedal will begin to react.  

The standard practice is to hook a tube from the brake bleeder to the slave cylinder bleeder. Open both bleeders and gently push the brake pedal. The clutch system is purged of air.

Once the pedal begins to react, the system quickly purges itself of all remaining air. Do a clutch adjustment at this point.

The clutch adjustment on the slave cylinder should allow about a half inch of free play at the pedal after the clutch is bleed.

Joe Alexander
Blacklick, Ohio

[JimVillers]

Joe ... Thanks.  I always learn something reading your posts.  It never occured to me jumper the brake bleeder.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[JimVillers]

Joe ... Thanks.  I always learn something reading your posts.  It never occured to me jumper the brake bleeder.

Jim Villers
190SL, 230SL 5-Speed, 190E 2.3-16 Kompressor, MGB 5-Speed

[ja17]

Thanks Jim,

The nice thing is that I learn from the group also. The body of shared knowledge is enormous. I guess I am lucky to have been around these cars when they were in production. Knowing how they were back then (new),  is helpful in putting them back now.

Joe Alexander
Blacklick, Ohio

[waqas]

Hello Joe,
A few weeks ago, I was pulling hair out trying to bleed the clutch... and then a search revealed the absolutely crystal clear instructions from you on one goes about using the brakes to do this, and voila! (saved my hair too!)

It's definitely nice to be part of a group that knows as much as this one does. BUT, there are always those 1 or 2 GODS of knowledge and expertise within the group that give just the right amount of reassurance to make shade-tree mechanics like myself completely comfortable with some of these repair jobs.... and you're definitely one of them! Thanks!

WAQAS in Austin, Texas

[al_lieffring]

I have used a trigger style oiler to bleed stubborn clutches. I had a new pump oiler that had NEVER been filled with oil that I kept full of brake fluid for just this purpose. With a short length of hose I would attach it to the clutch slave and pump fluid backwards through the system.



Al Lieffring
66 230Sl
Jones'n for a new gas tank

[Naj ✝︎]

Working the slave cylinder by hand works for me.

3 or 4 strokes of pushing the piston all the way in (with the clutch lever) pushes the trapped air thru the resevoir.

naj

68 280SL

[waltklatt]

Thank you to all who responded to the clutch inquiry.
I will go to the slave and pump the plunger a few times.  Hopefully this will be enough to get it right.
Thanks again!
Walter
1967 220SL-diesel

[waltklatt]

Update.
I've pulled the slave out to manually pump the plunger and found my hand and fingers wet.  So it's a new slave that will be installed.  
Guess 20/20 hindsight is to replace all 3 items at the same time: the clutch master, hose and slave.
Walter
1967 220SL-diesel

[jameshoward]

This is a daft question I am sure, but I don't know the answer.

I want to change all my fluids that haven't been done for a while. I changed the brake fluid last year when I did the lines. I think I also need to change the clutch fluid. I know how to top it up, and have read the procedure below, but how do I do it? THere is no air in the system and the clutch works perfectly. I think the easiest way os just to open the bleed valve under the car and using a pressure bleeder (I have a gunson one that attachs to a tire!!) just keep passing fluid through until the new fluid comes out of the bleed valve.

Can anyone please advise??

Thanks,

James

[rogerh113]

I just completed my clutch bleed with the 'naj' technique - thank you very much.  Bled out the old fluid and used the JA pumping technique, but could only get about 95% there - good clutch action, but weak pedal return.  Manually pushing in the slave piston resolved things immediately!!

Regards -- Roger