Clutch won't return - can't seem to bleed it properly

[Isaacsracing]

Looking for an answer to this. The clutch on my 1992 968 wasn't returning all the way to the top and in looking into things it appeared that the master cylinder was not doing well. I tried bleeding the system which provided mild improvement until the clutch left me along the side of the road.

I've installed new master and slave cylinders as well as new lines from the reservoir to the master and from the master to the hard line. I copied the arm adjustment from the old master to the new before I installed it. I've put new fluid in and used a pressure bleeder to get the system to work and also pumped with a friend to get bleed the system. The front of the car is raised on jacks. The rear of the car is on the ground.

With the pressure bleeder on with pressure the clutch performs as it should. When we remove the pressure, the clutch peddle only returns half way. The peddle is moving the clutch, but the peddle should come up.

I'm thinking the next move is to lower the front and raise the rear because many instructions say to bleed the clutch by raising the rear of the car. Can anyone confirm? Why would this work. I'll find out tomorrow I suppose, but I can't figure waht could be wrong. I'm tempted to adjust the arm on the master, but it would be a big change from where it was and I think that the adjustment is not the problem.

Thanks,
John
1992 968 street car
1990 911 race car.

[Backyardbodyman]

You could have air in your clutch master Cylinder that's not getting pushed through the lines. Wrap a rag around the clutch master line fitting. Have someone pump the clutch to build up pressure and hold down while you crack the fitting loose(quickly loosen and close). Do this a few times and do clutch slave cylinder again.

[Bradical]

Buy a motive power bleeder, the job is almost impossible to do without it. I was really reluctant to get one myself but once it came in the mail I had the clutch bled within 30 minutes.

Also, have someone depress the clutch and watch to see if its actually working. I matched my master cylinder too and I still had to adjust my spring return. It could be as simple as that.

[Isaacsracing]

Thanks Raymond. I'll give that a try. I'm a little worried about a quick open and shut because there is only a 1/12 turn available at a time on the fitting, but I'll have a a go.

[pdxfj]

Another option is to reverse bleed the system. Force fluid through the bleeder on the slave into the master.

Have to do this on motorcycles with hydraulic clutches quite often.

[Backyardbodyman]

Alot of people will bench bleed a master on vice before installing it otherwise you can get stubborn air pockets that are hard to push out. While someone holds pressure on the clutch just give fitting quick snaps open then close. This can take multiple times as some air pockets can be hard to get out. Do the master fitting a few times and then the slave a few times. Someone here also mentioned the adjustment on the clutch pedal. Make sure the push rod is being pushed all the way into the master.

[Isaacsracing]

As suggested, I did a little bleeding from the master cylinder directly. I attached the power bleeder, put some pressure on it (15psi), had a friend hold down the clutch and cracked open the main line from the master cylinder and sealed it shut again before the noises stopped. It didn't really seem like much air came out, but I did get fluid out. We repeated this 4 times. The pedal then returned like it should, until I removed the pressure form the bleeder. So we did it again. This time the pedal did respond a little better. I decided to try the car out. After buttoning up everything else that was apart a ride proved that the clutch operates, but the pedal returns either all the way or nearly all the way. In order to get it to return all the way, every time, maybe I need to adjust the spring or the attachment to the master cylinder.

[Bradical]

Sounds like you need to adjust it. You dont need anybody on the pedal with the power bleeder. In fact, if the clutch pedal is pushed down you cant push fluid through the master, so you might want to bleed it alittle with the pedal up and pressure applied on the power bleeder

[rmcdonnell]

I think reverse bleeding is often very effective. Especially if return holes are a bit clogged up, the reverse pressure helps to clear it. And air pockets are attacked from the other direction.

[CBR944]

Hi. Are you now bleeding the slave with the rear of the car raised? When I bled my new master and slave a couple of months ago I found that raising the rear definitely helps to clear air out of the system.

[bell]

I little trick not many people know about. .....
if you don't have any air in the system (and there's a good chance you don't )then you need to increase the volume of fluid in the system......you do this by using your hand to pump the pedal fast about 10 times, down up down up down up etc......
this will pull more fluid into the system and the pedal will return to the top instead of stoping short.....
try this before you waste more time bleeding the system.....which is probably already properly bled

[bell]

Fyi I've done this on probably 50 different cars over the years.....all i use is a vacuum bleeder for the initial bleed......i haven't touched my motive bleeder in years....

[Tazio57]

When using a power bleeder the pedal should be in the up position, not pushed down.

[Rasta Monsta]

Previous owner may have compensated for failing master cylinder by adjusting. Verify actuating rod adjustment. If correct, you have mechanical problem inside bell housing.

[PorscheChef]

This is the easiest way to bleed the clutch. It takes longer to remove the starter than it does to bleed the system. Works every time!

https://www.youtube.com/watch?v=wdf--suwqw0