OK, I've had a hell of a time with my 1985 and getting the clutch to behave. It has 104,000 miles on it and I had replaced the master and slave cylinders trying to resolve my clutch not wanting to disengage issues. Even ended up replacing the master under warranty only to have the clutch suddenly start misbehaving again when it got cold. Bleed at the slave cylinder and all I get is clear fluid with no bubble. Very frustrating. Flush the whole system again. It's worse than ever. Pump the peddle a while the fluid is black and bubbly. What is going on?

I'll start with the solution: I had to pull a vacuum on the reservoir. That fixed it 100%. Sounds bizarre but it worked.

Have to be careful you don't draw up the fluid as well. If you have a way to draw a vacuum on the whole thing it would be easy, but I had to keep my finger on the pressure release and hit the release as I broke the seal with the inlet so it could grab the fluid and the vacuum pump wouldn't. That and getting a good seal around the inlet were the only tricky parts.

The "self-bleeding" system activates when you let up on the peddle. I figured this out by observing the fluid as I had someone pump the peddle. I was getting bubbles and dissolved grease in the fluid each time the peddle was release and let sit. I figured I could just do this until it ran clear and I didn't get any bubbles. After an hour of working the peddle still no improvement. Still getting grease and bubbles. I had already pulled 12 oz of dirty Dot 3 out of the reservoir. Time to rethink my strategy.

I hit Wikipedia to refresh my memory on brake bleeding procedures and noticed that the standard shop method of bleeding is pressurized from the top down. So, I change my assumptions and decided to see if maybe there was a way I could get the master to stop bubbling and spewing grease into my fluid. I couldn't pressurize it but I did have a hand vacuum pump. Figured maybe drawing a vacuum might help.

So I cut a piece of tube very smooth and connected it to my pump. Filled up the reservoir, then pressed the hose over the inlet as hard as I could without it buckling and started pumping. Right away I was pulling bubbles. Then bubbles and black grease. Pull away while hitting the vacuum release on the pump and it sucked in about half the fluid into the cylinder. Now we're talking. I pulled the now dirty and aerated fluid out with a syringe, topped off with clean, and kept going.

2nd pass I got a chunk of something black and stiff as well as a bunch of grease. I think it was whatever was blocking up the system. I did this process a couple more times until all I got was full vacuum, no more grease, no more bubbles. I had used another half a quart of fluid by this point. Boom, peddle is better than it has ever been. No pumping, doesn't have to go all the way to the floor to disengage. Shifts like it's supposed to. I'm a happy camper.

I couldn't find anything like this online so I thought I would share and hopefully make someones life easier. I hope this helps someone else who had trouble bleeding their clutch system.

 

Thanks for posting, very interesting idea.

Might you share how much of a vacume you were pulling?

Also, I wonder if the idea would work with an alternate Clutch Master Cylinder reservoir top with a nipple installed and which could be swapped for the regular top when 'bleeding'?

In therory, the reduced atmospheric pressure (vacume) above the fluid could still draw air bubbles out of the slave and hose and eliminate the challenge of possible damage to the vacume pump.

Anyone have an extra Master Reservoir Cap and could try this (might even be able to market it)?

 

pretty cold up here in Michigan with no garage to work in, but there's no snow so I think I'll try this out tomorrow...I have an 85 that has some "quirks". Seems to be stuck in gear, the clutch will disengage just enough to start the engine and not plow into anything, but I can smell clutch nastiness and the fluid is horrible looking. I also have to go almost all the way to the floor to get there as well...hopefully that is one of the issues. Still checking out the alignment of the shift rods for the nash to make sure that they are in the right position [read neutral] as well. Thanks for the write-up.

 

One thing to note is that on the 84-88 you cannot successfully bleed the system using the conventional method with the slave cylinder bolted to the bell housing. With the slave mounted, the bleeder screw is not at the top most point, which will leave air in the system.

Simply unbolt the slave from the bell housing, tilt the cylinder to where the bleeder screw is the highest point, and bleed the system.

 

Could you post a picture of how you hooked this up. Seems like a great idea.