1G Clutch Bleed Secrets

[rdeis]

Evening, all. I've got a head scratcher.

My clutch suddenly felt softer while driving, and I couldn't get the car in gear. Left me stranded me at a stop light, pointed up hill. Ugh.. Anyhow, rescued and safe, I discovered no fluid in the master cylinder reservoir and some fluid around the master cylinder shaft so assumed a bad clutch master. Got a new one under warranty from the FLAPS, swapped it. DUring the swap, I discovered that the adjustment extension someone welded for me had let go, so the problem was actually linkage not hydraulic. But there were signs of leakage and the new one was a warranty replacement, so I fixed the linkage properly and finished the swap.

I'm kinda wishing I hadn't-- I absolutely can't get it to bleed. I use a pressure bleeder, and the last two times I've done this it was easy. This time no success.

Here's the story: I add fluid, pressure, open the screw until the drain hose has no bubbles, press the pedal a few times, press the fork lever a few times, tighten everything up. Start the car and it shifts, huzzah! Turn the car off, clean everything up, start the car again and it won't go into gear.

I repeated this twice.

Went home to the back-up car, pulled the working master and slave from that and installed them on the broken car. They won't bleed either. I barely got it to go in gear once. I even tried hooking up the pressure bleeder backwards to force fluid and air up to the master from the slave and I still got nuthin'. Depending on details, it gets stiffer or softer, with more or less clutch fork movement, but no matter what I do I there isn't enough to engage the clutch.

- Don't think it's a bent/broken fork. The fork doesn't move nearly enough. Sometimes not at all.
- I don't think it's the cylinders- I've tried two sets with the same result, and one set was working fine on a different car.
- I'd suspect a leak or failure in the lines, but I can't find any fluid where it doesn't belong. No new puddles under the car.
- If it's trapped air, then trapped where? Why isn't the pressure bleed pushing it out like it has on previous jobs?

What happened?

 

[rdeis]

Read this line from Pauleyman's thread: https://www.dsmtuners.com/threads/clutch-basic-101-a-clutch-basics-thread-for-everybody.459908/

"You could be over-adjusted and not filling the fluid capacity of the clutch master cylinder resulting in less fluid movement"

I'll buy that-- for others that have seen an over-adjustment problem, does it match my symptoms?

 

[diambo4life]

I think you still have air in the slave. They can be a pain to do.

 

[luv2rallye]

Read paragraph "Step Two: Next have person..." of https://www.dsmtuners.com/threads/clutch-will-not-disengage.460266/#post-153268772.

 

[rdeis]

Thx! Read paragraph 2, that's part of my standard procedure.

The slave cylinder was manually compressed each time the bleed screw was opened, usually more than once, until there were no bubbles in drain line, then the screw is closed with the slave cylinder still compressed.

So I'm doing something else wrong...

 

[rdeis]

Found Jack's link from a long time ago:

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A couple of the gurus here have mentioned that they don't like having the master adjusted as high as Jack says to here, but that video at least provides a test that lets you know you've gone too far. According to this, if you can't compress the slave with your thumb when the clutch pedal is fully released, you've over-adjusted and there will be problems.

I can't, so I have problems.

Jack's description doesn't seem to describe my particular problems, but either way I know this isn't right so its the next thing to fix.

 

[dwb]

Just so I understand the order of events

• clutch stopped disengaging and you found the master cylinder dry.
  • Did the pedal fall to the floor and not retract?
• You replaced the master
• during replacing the master it was found some linkage was broken. It was not specified what was broken
• You blead the hydraulics and confidently pushed out the pesky bubble in the slave

You have a couple variables here. New MC and new linkage. The clutch pedal assy has not been verified and could be another possible culprit.
Why did the reservoir go dry? You need to find the reason because it is a sealed system. Is the slave leaking too? What was the custom linkage that broke? Is the bore size on the new MC the same as the old?

I personally welded an extra nut to the MC shackle to give me another 1/4" of threads to compensate for worn pedal assy. You just have to watch out for "pump up" (too much extension, not allowing the internal MC bleeder to release).

 

[rdeis]

• Did the pedal fall to the floor and not retract?

No, oddly. It got suddenly softer, but still had some pressure and would retract.

You replaced the master

• during replacing the master it was found some linkage was broken. It was not specified what was broken
• ...
  I personally welded an extra nut to the MC shackle to give me another 1/4" of threads to compensate for worn pedal assy. You just have to watch out for "pump up" (too much extension, not allowing the internal MC bleeder to release).

I had done the same weld to the clevis/shackle as you to get more room for extending the shaft. That weld is what broke in the linkage. I believe that it "mostly broke" on the road, perhaps allowing the nut to bend away from the clevis and effectively shortening the rod? It left me with some pedal pressure, but not enough to release the clutch.

The dry reservoir is certainly not right, so (sitting by the roadside unaware of the broken weld) I assumed the master was bad and got a new one. The weld broke the rest of the way while I was removing the old master.

Is the bore size on the new MC the same as the old?

I can only assume- it was a FLAPS replacement under warranty. The new part is somewhat different than the old, but the part number matches 1G AWD DSM in their computer.

You just have to watch out for "pump up" (too much extension, not allowing the internal MC bleeder to release).

I did a similar weld extension for the new master, and am now I'm fairly certain that I have a "pump up" issue at this point. Hopefully that's the only issue.

 

[rdeis]

fixed the pump up problem, so the master is properly adjusted now, and still no joy.

This is really wierd.

 

[rdeis]

Aha!! There’s a really, really small leak at the flare joint to the slave.

I had to have the system fully bled, and closed up, AND have a buddy pushing on the clutch pedal to see it.

Small enough that it’s really hard to push fluid out, but really easy to suck air in.

I tried re-seating the joint and it won’t seal, so either the end of the line or the seat on the slave is damaged.

 

[rdeis]

Nope, no sign of bubbles anymore,,so that’s good, but it’s still not releasing.

I’m measuring 10mm of motion on the end of the clutch fork. How much travel should there be?

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[dwb]

What happens if you bump the starter with it in 1st and clutch pressed? Does it slip or lurch forward?

I don't have measurements but here is mine with a new clutch and flywheel (video at the bottom of this post)
Post in thread '1991 TSi AWD' https://www.dsmtuners.com/threads/1991-tsi-awd.540276/post-153927165

 

[rdeis]

Ok, I've figured it out. The "known good" master from the other car turned out to be bad, but that's not the real problem, it just helped confuse me.

Here's the diagnostic process I used:

Step 1: Do the initial bleed
Step 2: Adjust to the max, per Jack's video above
Step 3: Re-bleed, pressing the slave per @luv2rallye's link above
Step 4: Push the pedal to the floor and block it there. Wait ~10 minutes and check for leaks at all the hydraulic joints.
--> I don't have any. Fixed that issue!
Step 5: Measure the travel on the clutch release lever.
--> I get 13mm, which isn't enough.

Now the hydraulics are tight and right, so its someplace else.

Step 5: Push the pedal to the floor, let up to its natural resting height.
Step 6: Place one hand on the master cylinder rod, and then lift the pedal to where it stops using the other hand. If this movement is more than "barely detectable", get a straight ruler and measure the distance.
--> Factory service manual spec is 1-3mm
--> I measure 25mm. Bingo.

Now that's interesting, because it definitely had a "slipping/bending" linkage failure feel when it let go. If the clevis lever loosened and slowly slipped out of place, that's what it would feel like! I also noticed that the clevis lever stopped all the way forward against the spring. That seemed odd, but it didn't immediately register as "wrong" at the time.

So, mystery solved! Time to go read the pedal assembly rebuild threads!