so, we bled the system. and bled. and bled.
system is all stock components for a 1980 amc spirit. except the line, as that was NLA. that is 1/4 hydraulic hose with crimped IFF fittings at both ends. hose is routed in the only way possible, which puts a tight radius bend slightly above the top of the reservoir. we are getting good flow through the bleed screw at the slave, and very slight force on the pushrod at the slave. no change in clutch pedal feel, no clutch actuation, no air bubble, no leaks. I even pulled the slave out, held it in my hand, and was able to keep it from extending the pushrod with the clutch pedal depressed. tried this repeatedly.
my gut says that the master is bad, and bypassing the pressure internally. what else can I do at this point? how do I know what is actually bad?
is the hose going slightly above the reservoir causing issues?
is my lack of bench bleeding causing issues?
is the sky falling?
both parts are stamped girling. both are from rockauto. I know that the aster is 13/16, unknown what size the slave is, but it is whatever AMC matched to the master. its a pusher slave.
pushrod bottoms in the master with clutch pedal all the way down. clutch pedal still has travel left, but the pushrod acts as a travel stop.
I'm relatively certain that there is no air in the system.
Relatively certain there is no air? I'd start there. Actually, I'd start by pulling it and bench bleeding it, then figure out how to not have the loop that goes up, then bleed the whole system. And check for a very small leak somewhere at one of the junctions. Spray it all down with brake cleaner, let it dry, pump it up a bunch, look for any wetness.
Reverse bleed it, and bounce the pedal while doing so. If bench bleeding isn't a PITA with it in place, do that before the reverse bleed. Another thing that may help is to restrain the pushrod on the slave from moving while bleeding the system, if that's possible.
Clutches are always a pain in the butt to bleed.
One thing that I did for my RX-7 (which eats masters at a depressing rate) is to get a spare cap (easily available, see above) and drill a 7/16" hole in it. Then pop in a tire valve. Fill master, open bleeder, apply pressure with bike pump. Close bleeder before master runs dry. If there is still air coming out, repeat as necessary.
I bled the air out of the clutch hydraulics this way when I replaced the DOT3 with 75W90. (It actually worked to bring a bypassing master back to life. Felt a little odd in the summer, was undrivable in the winter - push pedal down, it stayed down for MINUTES 
)
I have a pressure bleeder, and I bought a rubber tipped air gun to use with it. Push the fluid up from the bleeder, and many, many curse words are saved.
You are fighting two things. First, is gravity- You are trying to force air in a fluid column down. That's tough. Second, you are pushing down on the pedal, closing the bleeder, letting the pedal back up, and creating a vacuum which will pull air past the seals in both cylinders. Second problem can be helped by letting the pedal up very slowly.
Pressure bleeder for the win here, I'm afraid.
Well, maybe not gravity. Is that what makes air rise in a fluid?
So, since every response is about bleeding the system more, am i to assume that the problem with this setup is air?
Is there any reason why I couldn't take the whole master/line/slave out of the car and bleed it all in the bench?
Dusterbd13 wrote:
Is there any reason why I couldn't take the whole master/line/slave out of the car and bleed it all in the bench?
Only logistical. If you can get the whole system out intact, that would probably be the most foolproof although rigging it so the master was the lowest point and the bleeder the highest would be tough.
Another thing you can try is just sticking a hose on the bleeder screw, running it up to the reservoir, and pumping the pedal (smoothly, not madly) a bunch. Like bench-bleeding a master but on the car. It's best to stick a little thread sealant on the bleeder screw so air can't get sucked back in through the threads, although Girling style master cylinders don't generally have a problem with that.
push the Slave closed then a couple rounds of duct tape to keep it closed, If it can be raised above the Master great, but if no way then either reverse fill/through the bleeder Or long slow pumps from the clutch pedal.when its bleed it will poke/tare through the Tape.or as Knureled said loop it from the bleeder to the Master,you still have to open and close the bleeder through out the process,until fluid is going back to master and hose is submerged.
Knurled wrote:
One thing that I did for my RX-7 (which eats masters at a depressing rate) is to get a spare cap (easily available, see above) and drill a 7/16" hole in it. Then pop in a tire valve. Fill master, open bleeder, apply pressure with bike pump. Close bleeder before master runs dry. If there is still air coming out, repeat as necessary.
im gonna be honest, this is genius. ill have to add that to my book of cool tricks.
Streetwiseguy wrote:
Well, maybe not gravity. Is that what makes air rise in a fluid?
Yes, gravity. It makes the fluid fall and displaces the air so the air has to go up.
So i think tonight i will pull it all back apart and try bleeding the system more. Put the slave in the air above the master, with the bleed screw being the highest point.
What precautions do i need to take to make sure that i dont make things worse?
Would vacuum bleeding or line looped to the master be the better bet?
On the bikes if there is any pressure on the M/C they will not bleed at all. Have to make sure the pedal is not resting too hard against the clutch rod.
Odd, I've generally had good luck simply filling the master with fluid and cracking the slave's bleeder, and letting fluid run through the system by gravity.
I do have a situation on my '66 Jaguar at the moment where the clutch would not release. After a bit of a drive, I came home, then went to move the car, pressed the clutch, put it in gear, released the clutch, and...nothing. After sitting for a while I came back and tried again, and this time the car moved. I suspect the rubber flex line was collapsing internally, causing a "stuck" pressure in the applied position. This can happen with brakes too, when a wheel seems to be stuck. A new line is on order, we'll see if it helps.
TL;DR - Check to make sure it isn't an issue with the hose. Possibly try bypassing it with just hard line all the way from slave to master, temporarily.
Edit: Also, absolutely "bench" bleed the master. I've tried shortcutting that, and it never ends up well. Hopefully it's possible to do it on the car- much easier.
NOHOME
PowerDork
6/6/17 2:59 p.m.
GTXVette wrote:
push the Slave closed then a couple rounds of duct tape to keep it closed, If it can be raised above the Master great, but if no way then either reverse fill/through the bleeder Or long slow pumps from the clutch pedal.when its bleed it will poke/tare through the Tape.or as Knureled said loop it from the bleeder to the Master,you still have to open and close the bleeder through out the process,until fluid is going back to master and hose is submerged.
I have to do this every time I bleed the slave cylinder on an MG Midget. Works.
Directions on my old grand prix were unbolt slave and push rod in and out to bleed back through the master cylinder. Worked better than any slave with a bleeder screw i ever tried.
Excuse me if I missed it, but what started the reason for bleeding?
Was something replaced and you're just bleeding or did the clutch stop working and you're assuming it just needs to be bled?
Everything you describe sounds like a bad master. In which case you should replace the master and slave at the same time anyway.
The reason for replacing was full manual transmission swap. So all the components are brand new. But we all know that new stands for never ever worked. Really seems like a bad master cylinder to me as well and I have another one on the way from RockAuto but I wanted to double check before throwing more parts at it.
Tighten the bleeder and pump the pedal over and over. Have someone watch the reservoir for tiny little bubbles. If you see them, keep pumping until they stop and then bleed as normal except with several pedal depressions between each crack of the bleeder. If you see no bubbles, chances are the return spring in the master is broken and the shuttle isn't moving back into position between pumps.
Dusterbd13 wrote:
The reason for replacing was full manual transmission swap. So all the components are brand new. But we all know that new stands for never ever worked. Really seems like a bad master cylinder to me as well and I have another one on the way from RockAuto but I wanted to double check before throwing more parts at it.
OK, so legitimate to ASSUME you started with good parts at least.
In reply to tr8todd:
We did try that just to make sure that fluid level was changing on pedal depress. No fluid level change that qe could aee.
Recent PITA with a Focus clutch/MC: My Brother had a tough time getting any satisfaction. I was only there for the final fix, which involved a second, new master, and according to online research, bleed only when the pedal was in motion. I.E., in the middle of its stroke. No "pump it up...Hold IT", as we all learned. I bled just a little squirt off as Bro-meister pumped. It worked. May be worth a try.
Another way of pressurizing the clutch master cylinder:
Could be air in system but Sounds like faulty master.
I take a large veterinarian syringe, fill it with fluid and push it in from the slave bleeder.
I also find that short quick stabs at the pedal can dislodge air as well.
I highly doubt that air can be pulled past seals when releasing pedal during traditional bleeding. If so, seals would likely be leaking.
