My mystery air leak; could it be the leveling valve?

I had one do the same thing. Just started purging air in the middle of the night while driving down the highway. Air pressure would quickly drop down then the compressor would pump it back up to 120psi. Within a couple of minutes. I had a spare and changed it out. That was 3 years ago. And now here all of a sudden within the last few weeks it's started leaking out that purge again. My truck has no air leaks, or had none, would hold pressure parked for a month but not anymore. Shut it down and walk back there you can hear it coming out the level valve. Within half hour I'm down to 60psi. It seems to stop there. I noticed I could use my hand to put ever so slight upwards pressure from underneath it and it stops leaking out air. I noticed the bushings in the leveling rod that actuate it have some slop in them. I wonder if those bushings need to be tighter and replaced or do you just replace the rod? I'm going to try adjusting it to see if I can eliminate it. Failing that I'll probably just replace the level valve. It's a bendix made in Mexico that I've replaced twice in 5 years already. The first one looked original. Anyways I'm hoping someone who knows see's your thread and can answer some questions.

 

I seem to have to replace my leveling valve almost every spring. (Not yet this year). And I get these leveling valves at Peterbilt.

And mine are not in the main road spray.

Apparently, cheap chinness valves.

 

My leveling valve is at the rear of my tractor but there is a small valve under my 5th wheel that was leaking and one day it just starting leaking really bad so I took it off and tore it apart and there was a diaphram that had a hole in it, naturally I didn't have anything to fix it with except duct tape so I made one and it's worked fine and that was at least 5 years ago!

 

There are air regulators in different locations. I buy a universal leveling valve for $60.00 & keep a spare. I had a air leak under 5th wheel one time, there is a big regulator & a real small one. the small one leaked. just make sure you replace the device that IS where the leak is. it is frustrating to me, that any part on my truck that is original would last 15 years, but to replace any part & put on new usually lasts no more than 2 years.

 

I don't have any problems with ride height so the rod is probably fine. Just sounds like a case of they don't make them like they used to with the level valve.

 

My level valve is a haldex not bendix.

 

A leak like this can be in the air bag itself. As the air leaks out, the suspension goes down, now the rubber on the bag is pinched stopping the leak. As the suspension builds air the leak is exposed again. Disconnect the linkage and put excess air into the bags, this exposes more of the rubber. Now spray the bags with soapy water.