MK4 O2J clutch bleeding issues

Hello,
I'm having a lot of trouble trying to bleed my clutch, first, some background:
One morning I noticed my clutch pedal felt odd and was engaging lower that usual. I kept driving it like that for a week or two with no noticeable change in the clutch behavior.
Last weekend I took a long trip out of town, everything seemed ok, but after parking for the night I noticed my clutch was engaging very low, and wasn't complete disengaging as it was very difficult to shift into first and second. The symptoms got better as the car warmed up.
Upon returning home, the clutch was engaging low but still working. However, the next morning I couldn't shift into first at all, the clutch wasn't completely disengaged.
I decided to try bleeding the clutch as it is the least expensive fix.
With the reservoir completely full, I opened the bleeder nipple, pushed the clutch down and had a lot of fluid exit the slave into the bleeder hose. The clutch stayed on the floor.
I closed the bleeder nipple, raised the clutch by hand then opened the nipple and pushed the clutch down again. This time I hardly got any fluid out. I did this for 15 minutes with no appreciable amount of fluid in the bleeder hose.
I found a helper and saw that the fluid would come out, but when I opened the bleeder after raising the clutch, the fluid would drain back into the slave cylinder.
I ended up getting a pressure bleeder, set it to 12 psi full of DOT 4 and opened the bleeder nipple. I had some fluid come out but it stopped after maybe 20ml was in the hose? I could have more fluid come out of the bleeder if I pushed the clutch pedal to the floor (where it would stay) but it would just drain back into the slave upon raising the clutch, even with the pressure on the fluid reservoir.
I tried all sorts of different things trying to get the fluid to bleed out, but only managed to get about 50-75ml out total.
One thing I noticed:
The only time I felt pressure when pushing the clutch in, was if I allowed all of the fluid in the bleeder hose to drain back into the slave cylinder. However, the fluid that would exit the slave was never more than what had drained back into it.
So, what would cause the fluid not to bleed from the slave cylinder with pressure on the reservoir?
Yet allow the fluid to flow when pushing the clutch pedal in?
Is it normal for the fluid to drain back into the slave cylinder?
Thanks for reading, please help!

Maybe the pressure gauge is faulty, I usually inflate the tyre to 20psi which works a treat. It sounds like a lack of pressure anyway.

My tire is at around 30psi, I tried setting the bleeder to 25 psi just to see if more pressure would help but it still wouldn't bleed

Have you tried taking the bleed screw all the way out to check it's not blocked? I can't think why else you'd have this problem, mine was really easy, just pressure connected, open bleed screw, let air out, tighten bleed screw and that was that sorted.

Owen81 said:

So, what would cause the fluid not to bleed from the slave cylinder with pressure on the reservoir?
Yet allow the fluid to flow when pushing the clutch pedal in?
Is it normal for the fluid to drain back into the slave cylinder?

Click to expand...

Owen,
So, what would cause the fluid not to bleed from the slave cylinder with pressure on the reservoir?

The fluid path is not open from MC to hose. Possible ideas.

Pedal is not completely up. If the pedal is down even slightly the port or valve is closed and fluid cannot enter.

Is it normal for the fluid to drain back into the slave cylinder?

Yes. With your foot off of the pedal it is an open circuit from the reservoir to the SC until you push on the pedal and the valve closes or the port closes.
I'm sorry I don't have a specific accounting of the MC in your car. I haven't taken one of them apart to inspect it. But all MC's that I have taken apart fall into one of two types. 1st Check valve or tappet style. 2nd Old school piston port.

AP/FTE has used a lot of the check valve style this design is pretty easy to ID because the input fluid port and output fluid port are almost stacked on top of each other, a slight offset. The piston port has an offset just about almost equal to the piston stroke length, noticeably longer.

Recognizing the design helps with the technique or how the MC responds. Example the piston port has a real small hole that the fluid flows thru VERY SLOWLY but the check valve has a relatively large hole and flows fluid freely.

Techniques.

I've done a lot of clutch bleeding by helping the bubbles do what they want to do naturally, go up. Make sure the pedal is all the way up. Simply push the SC piston trying to seat the piston all the way into its bore. This pushes a LOT of fluid/air back up and into the MC. Then slowly let it expand in your hand. IT will pull in a lot of fluid. Repeat this process for a few minutes.

Next, does your transaxle have a hole just forward of the fork are that the book says put a bolt HERE to keep the fork from moving off of the guide tube?
This really changes the dynamics of what is going on. If it does, put a bolt in it to block the fork from moving, confirm your work. Now two people. One at the pedal, one at the bleed screw. Modest pressure, hold, open bleed screw, close, repeat w/o pumping the pedal, just single strokes.

Pressure bleeding, reverse fluid injection and vacuum bleeding both dry vacuum and using vacuum to actually pull fluid are all valid techniques but sometimes you're fighting a trapped air bubble that sometimes requires physically tilting or positioning a component to allow the bubble to flow up preferably or sometimes down.

Good luck,

Gary

Update:
I could get some fluid out of the bleeder, however, most of it would always get sucked back into the slave. I ended up letting it settle back into the SC, then closed the bleeder and tried the clutch out. It felt great and the engagement is back up to 2/3 of the pedal stroke or so.
I must have gotten the air out, with the small amount of fluid I bled, but I don't think I managed to get all new fluid through the slave cylinder.
It's working great atm so I think I might just leave it.

Thanks for all of your replys! I appreciate the help