Hydraulic clutch problem

[BornWestUSA]

With my clutch slave adjusted so the rod is all the way inside and the Throw out bearing just against the pressure plate fingers, the clutch will not disengage.

The original builder had adjusted it way too tight and the clutch would slip on acceleration, I don't think it was ever set up "right".

I have a modern driveline slave kit and A Wilwood .7" master in my mk4. According to Modern Driveline I need 1.2" of travel at the slave, I only have .75"

The slave starts to move as soon as you touch the clutch pedal, the bleeding seems good, just not enough travel.

I have not measured the master cylinder travel yet, not fun on a completed car. Modern says it must travel 1.4" to get the slave to move 1.2"

Is it possible to adjust the master, or remove the master on a completed car??

[rich grsc]

Wrong size master, or wrong size slave
Need a larger mc, or a smaller sc

[Mike.Bray]

My MC for the cutch is a 0.812" (13/16) bore and works perfectly. I think your MC bore is too small.

[Jacob McCrea]

For whatever it adds I run a 1 1/8" Wilwood master cylinder and a 7/8" Speedway slave cylinder with the homemade bracket shown below. It initially seemed like I needed a smaller slave (or larger master) to get complete disengagement but the problem went away after the clutch and pressure plate wore together a little.

201626

[BornWestUSA]

On paper and per Modern Driveline the .7 M/C and the supplied slave should produce 1.2" of travel. IF the master moves 1.4"

Does anybody here have a Modern Driveline hydraulic set up that is working?

My next step is to see if I can check the master cylinder to see if I'm getting the full 1.4" of stroke.

[BornWestUSA]

OK. I measured the clutch pedal throw, it moves 6.25", installed in the Wilwood pedal box 340-11299 with a 6.25:1 ratio that means the clutch master stroke is 1". Not enough.

So as @Mike.Bray mentions above a 13/16 (.812) master should work, if it moves one inch it will push the 3/4 slave 1.175" by my math.

Now, if I can only swap the master cylinders in a fully assembled car.... but it has to be done.

[Alec]

Now, if I can only swap the master cylinders in a fully assembled car.... but it has to be done.

I had a brake MC fail a few weeks ago. I replaced with an exact match (wilwood 3/4 inch) through the top of the footbox. It only took an hour or so, not that challenging. I assume you have an access panel on top of the footbox in the engine bay? I have a MK4, hopefully your setup is similar.

Clamp off and then remove hyd fluid supply line from MC; wrap in paper towel to catch drips (and put some cardboard on the carpet in the footbox below to catch the drips)
Unscrew the line nut and remove the hyd line from the MC output, be ready with the paper towel
unscrew the pushrod from clevis attached to the pedal - this is a bit hard to grip with fingers and there is limited space for wrench movement (that goes for all of these steps, be patient, use the small movement then reset the tool).
Just 2 lock nuts hold the MC to the pedal box, they screw in/out from to the rear. Upper one is accessible from above with a small wrench, the lower one is easily accessible underneath (from the cockpit) with a long extension and wobble adapter on a ratchet.

Replace and repeat in reverse. But hook up the supply before the output so that you can easily bench bleed (into a paper towel) the MC before hooking up the hydraulic line to to the output.

Working on an MG pedalbox is WAAAYYYY worse. Good luck!

[OB6]

Now, if I can only swap the master cylinders in a fully assembled car.... but it has to be done.

Do yourself a favor and replace it with a Tilton.

[Mike.Bray]

Do yourself a favor and replace it with a Tilton.

I second that. The Tilton bolts right in so why take a chance.