Clutch - Master / Slave

[Tony Radford]

I'd like to know what master and slave cylinders are on my car. The slave is the external type mounted on my bellhousing. I replaced both of them a year or so ago. I seem to be getting a little air in the system every few days of use. I pulled the boot on the slave and it was dry. The level in the reservoir isn't dropping.

[Master]

Tony, Make sure the bleed screw on the slave is tight, you might have some air trapped in system from your change out earlier. Did this just start?

[Tony Radford]

Scott, it happened all of a sudden. I jumped in for a ride a week or so ago and the pedal was mushy. It pumped up and was OK for a short ride. I bled it later and it came right back. Now, after a few rides it's getting mushy again. I tightened the bleed screw after the last bleed. I don't see any signs of leakage and the level in the reservoir is near the top. I'll be pulling the boot on the master this week to check for fluid. It's not like there's much to the system.

[Master]

I would look towards the master cylinder, but if it is only a year old that seems odd. Do you have any heat shields protecting master cylinders? Do you have the brake lines near the headers covered with insulation?

[Brent]

Tony,

Take the top off of your master cylinder and put your finger in the fluid all the way to the bottom. If you get some black graphite looking material from the bottom of the cylinder you need to replace the fluid and the cylinder. The piston in the master uses an inverted plastic cup and a couple of o-rings. When the fluid breaks down or if you use a "high dot" rated fluid the lubrication qualities go away and the cup wears and then the piston rubs the cylinder wall and causes grooves and the black grit you find. This will allow the master to draw in air and possibly leak inside the boot.

[Tony Radford]

Thanks Brent. The fluid is pretty fresh. I had filled the system with DOT 5 and destroyed both the master and slave. I ran about a gallon of DOT 3 through the system to get the silicone stuff out, but all of my o rings were shot. I replaced both the master and slave and everything has been great for six months or so. One pump of the pedal and the air is gone when bleeding the system. Seems like it would be something down low. Oh well, it's just a matter of jacking the car up and screwing with it. I then have to look at my leaking Canton pan. I had a crack along the bottom, back seam that I had welded a year or so ago. Now it's leaking again. Plus it's power coated silver to match my polished engine. Damn, it it ain't one thing it's two.

Scott, it's just the clutch and I recently replaced the rigid tubing, routing it over the foot box and down to the slave. It's definitely not a heat problem. It's something simple and stupid. Fortunately, I'm stupid enough to trip over the issue sooner or later, after I've fixed several things that ain't broke.

[Tony Radford]

I checked everything over carefully today. I pulled the boot on the master and it's dry as a bone. I pulled the slave boot again and ran my finger into the cylinder. There was just a slight residue on the wall. I bled the air out again and the fluid is inky black on the slave side. The fluid in the master reservior is clear. The fluid is less than a year old. Is that normal?

[pgermond]

Doesn't sound normal to me. When I change mine it is slight discolored, but not black. Sounds lilk maybe the line itself has baked on residue from the previous fluid boiling (?) Whatever the cause, it shouldn't be black :(