SeanR

Was thinking more along the lines of a damaged Slave since there was no feedback pressure (clutch)

Don Carter

Ah, ok so slave not mounted but still attached to the metal line? I don't think that ever happened. Since there's no stop holding the piston in, I can how that might damage the seal as the piston travels too far out of the bore into the dust cover.

ROG100

Clutch Master was *** and the Slaves both FTE

SeanR

At this point I'd get underneath and pull the slave, hand pump it a dozen times and re-install it. Then go test it.

Don Carter

Sean, that's exactly what I did yesterday afternoon, it worked for about 2 miles. I may try it again after checking the dust cover for fluid.

Don Carter

There was fluid in the dust cover of the slave, so when the pedal went to the floor yesterday, it was the fluid escaping past the slave seal again.

I inspected the seal again, and it looks fine, but I did notice that it looks smaller than the first slave cylinder seal, from the slave where the piston got stuck, both are the same brand, from Roger.

Here's the seal from the 2nd slave where the fluid is passing the seal, notice how it's smaller than the piston.


Here's the seal/piston from the first slave that got stuck in the bore. Notice it is bigger than the piston and extends out past the grove it sits in.

I guess this is either some bad quality control on seals, or some swelling going on? Even if the Valvoline was causing the seals to swell, I wouldn't think it would happen that fast. Totally frustrated at this point. Did I mention that the MC piston is now stuck?

Mrmerlin

the first seal looks correct the aft end is slightly undersize of the piston bore,
the second picture the seal looks swollen.

you should remove the seal from the piston and look for damage if the spring in the MC has shattered then metal shards will go into the slave

Don Carter

Stan,

No springs have shattered and I'm not seeing any debris in the system.

I found your previous posts about Valvoline mixed with other brake fluids causing seals to swell and I think that explains some of my past problems. The system sat for a couple of months while I did TB/WP and I think this was enough time to swell the seals and cause both the MC and slave to get stuck in place. You would think this would be causing problems for all kinds of cars, but I'm not seeing much Googling on this.

I still don't understand why the most recent slave is leaking, but I'll get that swapped out, change to a different fluid and try again. Hoping I can salvage the current MC and get it unstuck.

69gaugeman

That section of the seal doesn't do the sealing anyway. The flare cup at the end does. If the seal is swollen it will not seal correctly in the piston groove and can leak past there.

ROG100

Don shipping you a new slave this morning to keep you going until we sort out what is happening - gratis.

jcorenman

Don,

I think the stuck pistons and swollen seals have to be related. And the only reason that I can think of for seals to swell would be fluid-related: wrong fluid, or contaminated somehow with some other solvents.

Now I understand that Valvoline makes good stuff, and DOT-4 fluids are all supposed to be compatible. And you probably haven't been flushing anything with other solvents.

But when the likely, unlikely, and improbable's have all been eliminated, then the only thing left is the impossible's...

My inclination at this point would be to flush everything with copious amounts of ATE blue, just to be sure. (Yes, brakes also, because they share the same reservoir). I realize this is a huge PITA, but I just can't think of any other reason for seals to swell and stick in the cylinders.

Thoughts, anyone?

Don Carter

Roger,

Much appreciated. Outstanding customer service as usual. I will ship back the most recent slave when I get this all sorted.

Jim,

I'm definately planning to flush the entire system at this point, brakes and all, and change to the ATE blue.

69,

I realize that the smaller diameter edge doesn't seal against the bore, it was just a good reference point in the pics to see that one seal is bigger than the other. You make a good point about the required seal against the piston. The newest slave seal, even though it appears smaller than the older seal, might be slightly swollen, which could be enough to lose the seal to the piston allowing the fluid to pass.

I feel better at least having some possible causes to these issues.

ROG100

Don we stock ATE blue if you need some because you can't get it locally.

BC

This slave and master issue with the dual disks seems to be related to the fact that our cars are getting to the point where certain new parts don't match what we took out. SEEMS. To me.

Don Carter

Roger,

I do need the fluid. Please send me what you think I need to fill the clutch and brakes and have some left over.