How to Tell If a Failed Clutch Master or Slave Cylinder?

I've been working on restoring a 1985 3.0 QV and had to remove and disassemble the motor completely to replace failed piston rings. The overall process has taken about 3 years, and now after getting the motor back into the car I'm having problems getting the clutch hydraulic system to work. I've bled the brakes and all is good there, but unable to get any fluid from reservoir back to the clutch slave cylinder. I've tried all of methods I've seen in other threads, including the two person method with holding nipple closed alternately while clutch pedal is pushed for over 30 min, and have also used a power bleeder to pressurize up to 15 psi. I have also attached the small hand vacuum pump to the nipple bleed screw on top of slave cylinder, trying it both solo and with another person pumping the clutch pedal to draw the fluid in via suction. No luck with multiple attempts on those methods, and tried to do the reverse method of squirting DOT 3 into the slave cylinder nipple but no luck there either - couldn't get the fluid to go into the slave at all.

Below are a couple of photos of the power bleeder connected to the reservoir, and my clutch master cylinder & reservoir. In bleeding the brakes I would see fluid leave the reservoir, but haven't been able to get any to leave while working this for the clutch - not a drop.....so I am suspecting there might be an issue in the master cylinder. Is it possible something has "gummed up" the master cylinder so that it doesn't pump fluid? Could the hose between the reservoir and master cylinder be plugged? Any way to check that? There are no fluid leaks of the master cylinder, either on outside of it or inside near the pedal. The pedal doesn't get stuck or go all the way to the floor, and comes back normally on its own after being pressed down.

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I'm completely stuck and not sure what way to proceed on this. The clutch hydraulic line was open at the slave cylinder connection while the engine repair was being done over the 3 years timeframe, so not sure if that could lead to this problem as the system would have been full of air. I tried disconnected the hose at the slave cylinder and continued the pumping & bleeding process, thinking that maybe I could at least confirm fluid to that point...but that has been unsuccessful as well.

Is there an easy way to confirm if the master cylinder is working, or if it is plugged up? Is there something I'm missing in doing this? I'm really stuck on this and not sure what to do next so any insights or suggestions would be appreciated! Thanks!

 

OK will give that a try. I haven't done anything yet specific to the master so will try that and see if fluid moves through from there, at least I will know if the master is good or not. Thanks!

 

Thanks Guido - from what it sounds like there is a strong chance I will need new seals,but will do the tests suggested and if needed will get them ordered asap. Thanks!

 

Hi, yes that is exactly what we did....3 times for over 30 minutes each time and once for over an hour...but no luck whatsoever. Fluid level never went down and nothing came through the slave bleed nipple.

 

Hi, I tried to purchase them on this site but they aren't available directly - they aren't listed in their webshop and no way to actually order them. I tried sending them a direct message via their web response page but it won't send. Any other suggestions on how to get a set? BTW my direct email is [email protected] if that helps... Thanks!

 

Hey everyone so a quick update. First, thanks for all the help, insight, and suggestions. I did the troubleshooting and found out the the hose between the reservoir and the master cylinder had literally disintegrated from the inside. When I disconnected it at the master cylinder and bled it for a while I saw all kinds of debris, bad fluid, etc so that was likely a contributing factor. The clutch master cylinder is inop - normal peddle movement but doesn't move any fluid. I'm going to the local NAPA auto parts store to get a replacement intake hose, and will get a new replacement clutch master cylinder as it's likely the hone on the inside was damaged by all the debris and new seals alone will likely not fix it. I have a replacement clutch master cylinder on order, so hopefully soon will have it fully operational.

Thanks to everyone for all of your help - I knew the Fchat community would be the right place to go for wisdom, insight, and help. I feel very fortunate to be part of a group that cares about the cars and is as passionate as I am about them. Thank you all!!!