ARB air leak?

Buddy Lee

Well-Known Member
Joined
Jan 16, 2007
Location
Knightdale, NC
Hi all, I'm hoping someone has run into this and has some thoughts on what could be causing this.

I have a Ford 9" with an ARB air locker. I bought it used and when I first got it. It had a leak due to a bad o-ring in the bulkhead fitting. Before installing the axle on my truck I stripped it down to inspect everything. While it was out I redid the air line fittings and replaced o-rings in the air collar. After testing everything to make sure there were no leaks I reinstalled it in the housing.

The first time I wheeled the truck it worked perfectly with no issues. We went back out this past weekend and the first couple of times I used it it worked great. Then on our 3rd trail my spotter told me it was not working so I disengaged and re-engaged the locker and all of a sudden the compressor kicked on non-stop and my air pressure gauge just kept dropping. I tried it again and it did it again. After making it out of the trail we drove it on the trailer and put it on jack stands to figure out what was wrong. Everything seemed to be working just fine with no leaks and the locker was engaging. We assumed I'd just stretched one of the air lines and it was leaking out of the quick connect fitting and headed back out on the trail.

Same thing happened got to an obstacle, hit the button and it started leaking again. Drove it back to the trailer and everything worked. At this point I was just scratching my head. After a few more trails I figured out that if I engaged the locker before I needed it everything worked and there were no air leaks. If I waited until I needed it then most of the time it would just leak until I was able to drive it some small distance and try it again. So I just got in the habit of engaging it as soon as we hit a trail where I thought I might need it and just ran the trail with it engaged.

So my questions is. What could be leaking that would only leak occasionally and what seems to be dependent on the position of the locker. Because if I drive it a little and try it again it will not leak and as long as it stays engaged it will not leak. Based on that I've ruled out the bulkhead fitting and the air collar o-rings. Is there something internal that could be causing this?

Thanks for any help.
 
Probably a leaking seal, likely the piston seal. That's what seals the sliding piston that engages the clutch gear and locks everything together. Possible the clutch gear is worn out, and the seal is now damaged from debris from the clutch gear. There may be a damaged spot on the seal seating surface that's causing a position-dependent seal leak.
If the clutch gear is prevented from engaging right away and there is a positional seal leak, you might have enough pressure loss that it's not going to engage at that point after the first try.

The rebuild kits have a new clutch gear and a new piston seal. They're mechanically very simple, with only a few areas that can leak air. The cause of the leak may not be that simple though.

I'd call ARB and see if they can shed any light on it.

Have you been trying to lock it under any kind of load?
 
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Fabrik8 said:
Probably a leaking seal, likely the piston seal. That's what seals the sliding piston that engages the clutch gear and locks everything together. Possible the clutch gear is worn out, and the seal is now damaged from debris from the clutch gear. There may be a damaged spot on the seal seating surface that's causing a position-dependent seal leak.
If the clutch gear is prevented from engaging right away and there is a positional seal leak, you might have enough pressure loss that it's not going to engage at that point after the first try.

The rebuild kits have a new clutch gear and a new piston seal. They're mechanically very simple, with only a few areas that can leak air. The cause of the leak may not be that simple though.

I'd call ARB and see if they can shed any light on it.

Have you been trying to lock it under any kind of load?
Click to expand...

Thanks, looks like it's going to have to come out again at some point. Personally I have not crash locked it or tried to engage it under load. I always make it a point to engage it while not moving. However, based on other things I've found after buying the axles I can't really say the same about the previous owner. So anything is possible. I know it did not have a lot of miles on it. But they could have been pretty hard miles...
 
So you're not moving slowly backward or forward while trying to engage? That's usually helpful, but shouldn't be the cause of your problem. That could cause the clutch gear to jam against the mating teeth, instead of meshing properly. That won't damage anything, but will prevent from engaging until there is a little relative motion to align things properly.
 
Couple possibilities inside...

A nick in the copper line, copper line broken loose from seal housing, seal housing o'rings leaking, bonded seal leaking
 
ol'Jeeps said:
Couple possibilities inside...

A nick in the copper line, copper line broken loose from seal housing, seal housing o'rings leaking, bonded seal leaking
Click to expand...

Some of those were my initial thoughts too. But after running it for the rest of the weekend I ruled out any issues with the lines or air collar. Basically, if it engaged and locked it stayed locked and did not leak any air. I could leave it engaged for the entire trail and the pressure would barely drop. Either way it will have to come back out.
 
Fabrik8 said:
So you're not moving slowly backward or forward while trying to engage? That's usually helpful, but shouldn't be the cause of your problem.
Click to expand...

Not initially, initially I would attempt obstacles before engaging it and then if I had issues or wheel spin. I would stop engage the front and try again. After I started having issues with it leaking doing this. I would engage it as I was approaching obstacles. So at that point I would either be slightly rolling or stopped and then driving up to the obstacle after it was engaged.
 
RD99? I seem to remember those having some issues with the engagement collar and being switched on under load. From what you are saying it sounds like it only works if it is engaged before it is under load, is that correct?
 
Metto said:
RD99? I seem to remember those having some issues with the engagement collar and being switched on under load. From what you are saying it sounds like it only works if it is engaged before it is under load, is that correct?
Click to expand...

I'm pretty sure it's the RD99. It seems like it only does it when I try and engage it under load. I know the first time it started leaking I was under load, had the locker turned on but it was not engaging. Then when I turned it off and back on again it started leaking air. I'll have to experiment more next time I take it out.
 
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