porschesam

Hello, my clutch has been working fine. I decided to flush the brake fluid from both the brake system and clutch. I'm using a Motive Power Bleeder. I pressurized to 10 psi and loosened the nut on the slave cylinder. Fluid was coming out then I got a blast of air. I might have gotten air in the system from low fluid in the resevior and in the Power Bleeder. I topped off the resevior and continued. I now make sure that the fluid level is always high. I get new fluid coming out of the slave when I crack open the nut. When I remove everything I still get a clutch pedal that goes to the floor.

Is there air trapped in the system or did the pressure of the Power Bleeder blow out a seal in either the slave or the clutch master cylinder?

HELP!

gruhsy

you still have air. you can find a post I had.

best method to start is using the old two person pedal method then switch to motive.

will post tomorrow if you cant find my long post.

blodstrupmoen

Or use both the power bleeder and "the friend" pumping the pedal. Just be careful not to push to much pressure on the system.

Turbo17

Here's some things I learned while struggling with this:

Jacking the rear end of the car up as high as I could helped. The slave bleed is at the top back of the slave cylinder, and that cylinder is nearly level. A tiny bit low rear end and you get a bubble at the front end of the slave you can't get out. I've even resorted to removing the slave and tilting it rear end up to bleed it.

The master cylinder has a front volume and a rear volume. Both have to be completely bled and to do this you really need someone to move the pedal back and forth. If the pedal is up, the reservoir and pressure bleeder feeds into the front volume only. If the pedal is even slightly pressed down (when properly adjusted) it feeds into the rear volume. Make sure the pedal is adjusted so that it's off the master (final adjustment should be barely off, but during bleeding you can overdo it a bit) or you won't ever get fluid directly into the front volume. I found it works best to make sure you pressure bleed with the pedal both forward and back to directly supply both the front and back volumes. There is a connection between front and back, but it's not all the way at the top, so bubbles get trapped and won't move from one to the other.

In theory the pressure bleed should push the bubbles down to the slave from the master, but you're working against gravity. Pumping the pedal also helps this, but it can still be very hard to get bubbles out of the master.

I found two solutions if pumping the pedal doesn't work. Pressure bleeding from the slave will push air back already in the master or in the master to slave line back into into the master and out of the top of the master into the reservoir. Again, you must have the pedal in both positions. to bleed both front and rear of the master. You have to be careful not to introduce air at the bottom if you bleed this way as I can never seem to get all the air out of the slave when bleeding from the slave.

Sometimes air bubbles will will just work their own way out of the top of the master overnight or with gentle motion of the pedal. If I jack the car rear, pressure bleed from the top while moving the pedal slowly to open both main volumes, the slave bleeds easily, but I still often leave air in the master. Then I let it sit, or start the engine to get some vibration, and perhaps move or wiggle the pedal slightly (avoiding pushing air into the line to the slave) and I can get the air to move up to the reservoir from the slave.

If that fails, I resort to reverse pressure from below, but I have to be careful to apply pressure from the top first to eliminate all air at the slave connection below, then apply the reverse pressure. I've tried suction from the top after pressure bleeding from the top (leaving tubing at the slave into a bottle of fluid), but that sometimes pulls air in through the slave bleed threads. I've managed to bleed by alternating pressure suction only from the top, but my current preference is this:

I've got two clear plastic bottles of fluid - one at the top and bottom (mayonnaise or PB jars). Each bottle has two brass tubes extending through the jar top. One is long and extends into the fluid. One is short and is used to pressurize the bottle and force fluid into the long tube. The upper bottle is sealed to the reservoir (made a sealed cap of rubber sheet and hose clamp for the reservoir), the lower bottle to the slave bleed nipple. The whole thing cost me less than $5 for the hose and tubing.

I take low pressure air hose and pressurize the top bottle to pressure bleed out the slave. The car is jacked at the rear. I move the pedal back and forth - never touching the bleed screw. When bubbles stop coming out of the bottom, the slave is bled and the tubing is also filled with fluid so I can reverse bleed. I then pressurize the lower bottle and again move the pedal a few inches back and forth. This bleeds the master front and rear. You can't see bubbles in the reservoir, so I just bleed a lot.

I'm sure others are better at this than I am, but I've completely disassembled both master and slave, and struggled with bleeding enough times that at least I now know how it works and what I've done wrong before. It's still not easy for me so just take these comments as "what works for me."

onspeed

If you follow the line from the master cylinder to the slave, there's a connection along the firewall. When I changed my master/slave cylinders, I tried bleeding from the slave forever to no avail. I decided to try bleeding from that connection for a bit instead, and I got pedal pressure within like 4 pump routines. Just a suggestion.

Turbo17

I did that once also. It seems very hard to get the bubbles down that line from the master to the slave and out at the slave bleed. It was sort of messy and hard to reach that point, but it also worked for me. That's part of the reason that I ended up reverse bleeding each time - to work with gravity instead of against it in that vertical line.

boerge

Trubo17,you deserve a phd in 944 clutch bleeding! Thanks.

ramius665

There's another option here: Replace your clutch lines with AN lines

Turbo17

I struggled with bleeding the clutch and read lots of other posts from people having trouble. I ended up opening and cleaning out crud from both master and slave. I didn't have to replace any seals or parts, but there was lots of crud that needed to be removed and some corrosion in the area holding the spring where the piston didn't slide. I watched a factory tech video on bleeding a very similar (BMW or Mercedes?) clutch system that recommends doing it all by reverse bleeding using a clean oil pump can (one of those with a pump trigger), but that system just didn't work for me on the 951.

BTW, the pressure bottle I described at the top for bleeding the clutch is great for bleeding the brakes, too since they share the same reservoir.

porschesam

To all. I jacked up the right side of the car so that the brake fluid would flow to the clutch side of the reservoir. I pressure bleed from the reservoir and finally I got all the air out of the system. I bleed with the clutch pedal in both the up an down positions. Thanks for the help!