Axle blow off

[Mad Deranger]

I have a curious problem with my rear axle blowing out oil. I checked the vent and it blows clear with no oil residue. Next, I hooked up shop air and tested for CTIS seal blow by. I ran a deflate/inflate cycle and had no air escape from the axle vent. My tires hold their pressure and the CTIS controller shows no faults and works as it should. Tire pressure is balanced on all tires.

I had this problem when I bought the truck and I replaced the seals on both hubs and it did hold but 500 miles later, same thing. I am all set up to do them again but before I do, I want to think this through. If my seals are bad, I would lose tire pressure. It would escape through the axle vent. I don't see it with a static or dynamic pressurization. Is it possible that oil is being siphoned out through the quick release valve?

 

[Suprman]

The ctis wheel valves hold back the tire pressure. Where is the oil coming out of?

 

[coachgeo]

ignore this post.. I didnt read close before posting ..

 

[Ronmar]

Like Superman said, The wheel valves are only open and the axle seals only see pressure when the system is actively checking, inflating or deflating. All other times, the system is de-pressurized and the wheel valves are closed…

The problem with troubleshooting leaks on CTIS using the controller is that it doesn’t stay pressurized for all that long. if you access the PCU behind the passenger kick-panel, disconnect the line that runs from the PCU down to the wheels and attach shop air there, with a regulator set to say 55PSI. This will pressurize the entire system and you can hold it at that pressure for as long as you want to do a detailed leak check. Then you can put a baloon or rubber glove taped over the axle vent line and watch it for a while to look for leaks. It could also be that it is leaking only when the wheels are rotating…

 

[Keith Knight]

I had a similar problem, I’ve owned the truck for over 5 years driven it almost 10,000 miles the one time a short 7 mile trip after parking found gear oil leaking out of the vent tube pretty badly checked all the normal stuff cleaned it all up and it hasn’t happen again. Never could come up with a logical reason.

 

[Mad Deranger]

When CTIS pressurizes the supply line, what would it pressurize to? 120 or selected tire pressure?

 

[Ronmar]

When CTIS pressurizes the supply line, what would it pressurize to? 120 or selected tire pressure?

The PCU uses whatever pressure the wet tank can provide, but with the restrictions and the tires ability to absorb air, all the system plumbing and axle seals don’t really ever see peak system pressure .

If you connect air like I described above on the PCU output, you can only apply air within the pressure limits of the tires, as they will eventually fill to whatever the regulator is set for. An over-inflated 48” split-rim would be nothing short of awesome when it lets go

You could give it shots of 120 like the PCU does for testing, just don't leave it turned on and keep track of the tire pressure…

Here is my old manual CTIS controller. You can get an idea of what pressures the PCU and system plumbing sees in operation…

 

[Mad Deranger]

Thanks Ronmar,

I am trying to get why my seals keep blowing out. Do they fail at 60PSI or are they failing when the system applies tank pressure? I would like to keep the system operational but not at the cost of constantly blowing out seals. I just got back from borrowing a blow down tester and look what followed me home...

 

[Ronmar]

Now that crap right there is why my wife rolls her eyes at me…

there are people running 85-90 PSI tire pressures on these things without issue, so it is hard to say why yours are having issues. You might have a flaw in a hub that eats seals…

 

[Mad Deranger]

It is ether that or I misinstalled. Quite possible. I'll let you know what I find. Thanks again.

 

[Awesomeness]

One of the axle seals is two pieces, and people have accidentally left one part of it installed while replacing it. Then it damages the new seal, or prevents it from installing correctly/completely. Maybe that?