I am beginning to wonder if my mcleod master cylinder is bad. It is new, but I can get it to work at all.

I used a mighty vac and inserted one of the cone adapters into the outlet at the bottom of the master resevior. I attaching an extra coupler from another slave cylinder I had to the high pressure line coming out of the master and connected a piece of hose to it and stuck it into a can of brake fluid. I pumped the clutch letting fluid flow the correct direction then used the mighty vac to suck fluid back up through the system until I saw no air. I pumped the clutch pedal many time throughout this process and saw a lot of air come out of the system in each direction. I did this many times. I then reconnected the master to the slave and bled the slave by connecting the might vac to the slave cylinder (I have a one way brake bleed fitting on the end of the hex tube) and sucked from the slave cylinder direction and pumped the clutch pedal while someone kept the reservoir full. I still can not get the clutch to disengage at all. It is a brand new spec clutch, but that should not matter. The clutch pedal has almost no feel and seems to leak down if you hold it to the floor.

Has anyone ever heard of a new mcleod master cylinder being bad? This all that is keeping me from getting this swap on the road for the firt time.

impala swap

thanks,
scott

 

When my master was not connected to the slave, I could not compress the Master cylinder. What does yours do? Look for leaks.

 

Mine is connected and has been bled many time in the past few days. It is now to the point that it will disengage the clutch, but will quickly leak down and reengage the clutch if you hold it to the floor. I can still hear what sounds like are in the system if I am close to the master when i depress clutch pedal. I am hoping it will quit leaking down when I get all of the air out.

Mine was very hard to press down when it was dry (on the bench), but it was possible. I never knew this thing was going to be this difficult to bleed, or I would have done a bench bleed first.

 

i installed one in a customers car and about a week later the clutch pedal got stuck down to the floor, i ended up putting the revised GM master and it worked just as well if not better than the McLeod

 

If this happens while engaged but not when not engaged then maybe it's the slave. Do you have a puddle under the car? I have a Mcleod and it works great.

 

I spent a lot of time trying to get this to work only to find out I had a “new” bad Mcleod master cylinder.

I had a mightyvac plugged into the reservoir using one of the cones it comes with. I drilled and tapped the bleed screw on the slave cylinder (over the input shaft 2001 GM) so I could connect a hose to it. I put the bleed screw hose into a bottle of brake fluid. I proceeded to pump oil through the system one way and reverse flowing the oil back up using the mightyvac. I must have moved gallons of oil but kept getting air bubbles. When I closed the bleed it would disengage the clutch for about a second. It would feel like oil was leaking past the piston in the master. After spending the whole weekend trying to get this to work I gave up and called Mcleod yesterday. They offered to send a new master, but I only wanted a rebuild kit since I wanted to avoid having to remove the master. After getting off the phone I drained the oil and pulled the piston from inside the cabin.

Good news: No scoring on the cylinder walls.

Bad news: Someone forgot to install a seal cup in front of the piston.

The only seal I had was from the close tolerance of the piston itself. I think my bleeding method works great, but there is no way this was ever going to work. I think I was getting air sucked in past the o-ring that seals the piston preventing oil from leaking into the cabin. I only was air bubbles when I hit about 25 in/Hg. This must have been the limit of the o-ring.

http://shiggins.bounceme.net

PS – Red at Mcleod has been very helpful.