Modern Driveline Hydraulic clutch conversion

[Foghorn]

BLUF: I can’t get the clutch to disengage.

I have bled and bled and bled…going on weeks now. Tried multiple different methods: traditional press pedal and open bleeder, close bleeder & release pedal = no indication of air in the line. Tried MDL’s force fluid technique, again, no indication of air in the line.

At this point, I’m ready to tale it back apart and put a cable back on it!

Any ideas or troubleshooting tips would be appreciated.

 

[MG0h3]

Never dealt with one of these in an aftermarket application.

Does it have an external slave that moves the fork? Or is it integrated into the TOB?

Either way, you’ve bled both the master and slave/TOB?


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[01yellercobra]

Is it a hydraulic TOB or a ram that presses on the clutch fork? Is the fluid leaking out somewhere?

 

[Foghorn]

It’s a hydraulic throwout bearing.

I have bled both master and slave, no leaks that are readily apparent.

 

[MG0h3]

And does the TOB move at all or what exactly is happening?


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[Blkkbgt]

Have you tried pinning the clutch pedal to the floor and leaving it over night to see if any air escapes?

You can also buy adapters for the reservoir that will allow you to put a vacuum on the system with a brake bleeder.

 

[wckdvnm]

Going to sound cliche but have you been able to contact support for that company? Because I am considering that kit too.


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[vr4]

Is everything spaced properly? Have you verified the tob is actually moving?

 

[Foghorn]

Have you tried pinning the clutch pedal to the floor and leaving it over night to see if any air escapes?

You can also buy adapters for the reservoir that will allow you to put a vacuum on the system with a brake bleeder.

no, but it’s worth a try. more to follow…

 

[Foghorn]

Is everything spaced properly? Have you verified the tob is actually moving?

yes. TOB moves, but not enough to release the clutch. Tech support claims this is evidence of air in the system.

 

[Foghorn]

Going to sound cliche but have you been able to contact support for that company? Because I am considering that kit too.


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Yes. Tech support is available and have been as helpful as can be over the phone.

 

[Foghorn]

And does the TOB move at all or what exactly is happening?


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TOB moves as soon as the pedal is pressed. I can’t get it to move enough to release the clutch.

I have no indication of air in the system using multiple bleeding techniques.

 

[ToddW702]

Is the feed from the master cylinder connected to the bottom of the bearing? I have had to bleed two of these and the first one was similar to your experience. I had to buy a little hand pump vacuum pump deal and suck the air out through the master cylinder. This was after doing what you have done. The little stopper with the syringe hole is where I plugged in the vacuum pump and it worked pretty good. The second one I had was very easy to bleed and I can’t tell you why. The first one lasted 500 miles so maybe there was something wrong with it in the first place.


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[Foghorn]

Is the feed from the master cylinder connected to the bottom of the bearing? I have had to bleed two of these and the first one was similar to your experience. I had to buy a little hand pump vacuum pump deal and suck the air out through the master cylinder. This was after doing what you have done. The little stopper with the syringe hole is where I plugged in the vacuum pump and it worked pretty good. The second one I had was very easy to bleed and I can’t tell you why. The first one lasted 500 miles so maybe there was something wrong with it in the first place.


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yes, the MC hose is on the bottom and the bleed hose is on the top. I have vaccumed the bleed hose, but not the MC feed hose.

FWIW, MDL says vacuum will damage the slave cylinder (haven’t verified this with Tilton) and not to bleed it that way….but at this point, the car has been on jack stands for two weeks.

 

[Foghorn]

Thanks for all the suggestions. At some point I have get past the “if at first you don’t succeed, try, try again” & move to Einstein’s definition of insanity…

Mechanically - this was part of a T56 magnum tranny upgrade. I did not index the bellhousing. How much misalignment would cause the clutch to bind?

Pressure plate / clutch mis-match?

Any other ideas? I’m getting ready to pull the trans for the second time…

 

[01yellercobra]

Index shouldn't matter with just moving in and out. Are you able to measure how far the TOB extends? Find out how much travel it has. Maybe it's fine and you just don't have things spaced correctly.

 

[shurur]

Sorry you are having such a problem.

So this is the system with the master cylinder and a TOB (slave) that is in the bell housing, vice the external slave that pushes the clutch fork?

It sure sounds like air is still getting in somewhere. What are used for the hose connections? AN fittings are tricky.

 

[Foghorn]

Threw in the towel and pulled the trans back out. After three times in two weeks, I can do it in just over an hour .

I found that I had pinched one of the steel braided lines - I don’t remember which one (MC or bleed as I type this several hours later), but at least I found something wrong…

I am going to test the pressure plate and index the bellhousing before I put it back together.

I’ll report back when I get all that completed.

 

[shurur]

Threw in the towel and pulled the trans back out. After three times in two weeks, I can do it in just over an hour .

I found that I had pinched one of the steel braided lines - I don’t remember which one (MC or bleed as I type this several hours later), but at least I found something wrong…

I am going to test the pressure plate and index the bellhousing before I put it back together.

I’ll report back when I get all that completed.

Sounded like you were taking on air somewhere. Good troubleshooting!
Glad you found it.

Please follow-up with a review of pedal pressure, pics of valve cover clearance and such. Thanks for being on the bleeding edge of the MDL kit!

The folks want to know about this kit.!

 

[Foghorn]

Update:

It’s important to make sure that there is no preload on the master cylinder during the bleeding process. Preload will close the MC transfer port and you won’t be able to use the MDL one man bleeder kit.

My issue was that I was only getting 1.2 inches of travel on the MC when it needs 1.4 inches (less important with the .75 bore MC, but critical with the .70 bore - PM me if you want the math).

The “ramp assembly” has to be pushed all the way up to ensure no preload on the MC. Once bled, I took all the slack out by lowering it (the mounting holes are slotted) and now the clutch releases. It’s down about an inch off the floor, but it feels acceptable - haven’t driven it yet. More to follow…