ax15 master, air, or slave?

Backstory: Just swapped in an ax15 in place of my ba10. Install sucked as I have never done the swap so I did a lot of rock auto orders and local parts runs for all the parts but the actual install was fairly straight forward and went ok considering I didn't have a lift or trans jack.

Parts: Used trans and transfer case from good running cars and from people I trust.
New clutch kit with internal slave from Luk.
New custom hydro line stainless steel with plastic coating
New clutch master cylinder from napa

Symptoms: Everything worked perfect and I loved the new feel of the ax15 for 2 weeks. Then I went off roading in the mountains for a day and a half with nothing too crazy and didn't have to ride the clutch too much and it worked perfect. On the way down the mountain I noticed the trans not wanting to go into gear as easily. With traffic in southern california for a good part of my 2 hour drive home, by the time I hit the last stoplight before my house I couldn't get the trans to shift into gear with the car running. I had to turn it off and start in first and I cruised into the driveway in first.

Now pushing the clutch pedal will not disengage the clutch all the way. When I push the pedal it doesn't engage until half way down and does not have the normal pressure even when it does engage at the half way point. I tried bleeding it thinking maybe jostling it off road broke a few bubbles free. Bleeding (a lot) got bubbles at the same exact position of the pedal movement every time. No good. Swapped master cylinders under warranty hoping it was that. No change. Sprayed soapy water on the line connections and got not bubbles or any of the soap being sucked in.

So unless I am missing something, I am left with the slave being bad. It is a Luk brand internal slave that came with the clutch and is 2 weeks old. There is zero leaking from the bell housing. All I read in forums and reviews was Luk is a solid brand for clutch parts. It seems weird to have a slave go bad in 2 weeks. Before I go through the pain and time of dropping the trans again does my diagnosis seem right or am I missing something obvious? Thanks

P.S. I did bleed the clutch twice with two brand new master cylinders. And I do not have enough money to get an external slave bell housing and parts right now.

On my '96 AX-15 (external slave) the whole system is supposed to come as a pre-bled system with no bleeder screw. The bleeding method IIRC, is to just pump the pedal like 30 to 50 times. Another thing you may want to check for is a bent clutch pedal Z-arm. They're known to get tweaked and screw up the engagement/disengagement of the clutch. That's what happened to me, threw all new clutch and master/slave into my '96 (the throwout bearing was shot and needed to be replaced anyways.) once everything was back together, the clutch still wouldn't disengage. Turned out to be a bent Z-arm.

Well my clutch pedal actually broke not too long ago and i got a non-broken one from the junkyard and had it welded all the way around and reinforced so it is in the stock position. The master cylinder has good engagement by hand but somewhere in the clutch/line/slave assembly there is air being sucked in but no fluid leaking out. Im definitely am leaning toward dropping the trans to check the slave. I just really dont want to if i dont have to.

The only other thing you could try is pulling a vacuum on the reservoir for 10-15min. I've had pesky bubbles in systems that this works on. Other than that I'd consider slave.

Are you a 1000% sure the bell housing is seated to the engine block?

Hypoid said:

Are you a 1000% sure the bell housing is seated to the engine block?

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My immediate thought was only an idiot wouldn't have tightened all the bolts and double checked, then I thought wait, Ive done some pretty stupid mistakes before so I just checked. But yep it's all good and connected. Thanks

ljobbins said:

My immediate thought was only an idiot wouldn't have tightened all the bolts and double checked, then I thought wait, Ive done some pretty stupid mistakes before so I just checked. But yep it's all good and connected. Thanks

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I had one loosen up over time. It trashed two starter drives before the clutch pedal went down and stayed down (different brand vehicle). That is when I saw the problem. :dunce:

Re: ax15 master, air, or slave?(update)

UPDATE:

Finally got space to drop my tranny to look at the internal slave.

Before I started I rechecked all connections from the plunger on the master cylinder all the way to the bleeder screw on the slave and then I bled it one more time and there was no change. Something was still bad.

So I dropped the tranny and pulled the master cylinder and hydro line and slave and put it all together outside the car and bled it and it still gets air in somewhere bleeding it outside just like normal.

So now I decided I would fill a bucket of water and then try submerging one at a time to see if I still got air when I bleed it. I tried all 3 pieces underwater separately and I still got air in somehow but never anything coming out when its under pressure.

So after being frustrated I drained the brake fluid and filled it all up with water with red food coloring to see if the red came out anywhere if I stuck things under water. Nothing, nothing, nothing.

So I am missing something because I have a complete clutch hydraulic assembly that pulls air into the system but puts nothing out. If I gravity bleed it I get full correct pressure for one cycle then air is back in the system. It seems more like the master cylinder to me but this is the 3rd one right now. The original, and now two new from napa.

So I have a two week old slave cylinder, a brand new master cylinder and a brand new stainless steel braided hydraulic hose. One of them is bad. HELP!

I feel your pain, but don't have anything to offer, sorry. The only thought is to pick up a pre-bled set -MC, line and slave.

David Bricker / SYR

Internal slave or i would love to get a whole ready to go kit.

Iirc internal slave must be disconnected to remove/ reinstall from thw bellhousing. Therefore they are not available as a pre bled unit.

Ona buddies 95 yj, we gravity bled, pumped, vacuum bled, manually bled, rinse, repeat.
Eventually got it bled over a couple days

souske said:

Iirc internal slave must be disconnected to remove/ reinstall from thw bellhousing. Therefore they are not available as a pre bled unit.

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Could very well be true. Since I have external, I try to to think about internal slave cylinders. Looking at the Rockauto site, it does not show the assembly for internal, only fro external.

David Bricker / SYR

There is an o-ring where the line goes into the MC. Mine leaked a tiny bit and did exactly as you were describing for years. I think it somehow sucked air in at that spot.

XJ_ranger said:

There is an o-ring where the line goes into the MC. Mine leaked a tiny bit and did exactly as you were describing for years. I think it somehow sucked air in at that spot.

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Was there any fix to that problem? I was looking around for a master cylinder that had a screw flare fitting instead of the push on with o ring and havent had any luck so far finding one.