Have an old nissan truck. < 1989 >
My clutch fluid went dry and picked up a lot of air in the system. I was attempting to bleed it out and tried to loosen the upper bleeder valve. It didn't budge except for snapping off flush in the housing.
My question - Is it possible to bleed the system using just the lower bleeder, or am I going to have to drill the upper one out ?
I suspect you already know the answer. Air travels up, sorry.
I'm guessing the chances are pretty good you can get a sufficient bleed using just the slave bleeder. If you do it fast enough the master will act like a pump and just push the air thru because it will be drawing in a solid fill from the reservoir each time. Just make sure the reservoir is topped off. Hydraulic clutches are much more forgiving of a little air than brakes are.
Moot point, the cylinders need to be replaced anyway! The fluid didn't evaporate and I've found that if you just replace one, the other will start leaking shortly thereafter.
Follow up: Just using the lower one worked. It worked just like you said, pumping fresh into the system and pushed the air forward and out. One person on the pedal, one with a fresh bottle of fluid at the reservoir, and me at the bleeder. We just kept pumping and filling until I saw the color of the fluid change, and then I tightened the bleeder.
Dried everything off and gave the clutch a half dozen strokes. The piston boot on the slave started to get wet after that. Now I know where the fluid went in the first place. I'm going to have to replace the slave, but now I can at least keep an eye on the fluid level until it gets done.
I'd highly recomend you replace the master at the same time. Been down that road too many times and I refuse to just replace one anymore, it always comes back with the other leaking in a very short period of time.
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