Ornery Tag Axle

I've just finished reading Jon's comments in another thread in which he stated that he never lifts his tag axle except under extreme circumstances.

Yesterday, I pulled into a campground that had some very sharp turns and I lifted the tag while I got through the last turn, then promptly lowered it while maneuvering at a very slow speed.

After I backed into my parking spot, I had trouble leveling and finally concluded that the rear end was sitting very log with the mud flaps bent. There was clearly a lack of weight on the tag although it was firmly on the ground.

What made the situation odd was that I could not raise the rear end off the mud flaps. With the engine running I tried each side individually and they would not lift more than an inch or two. The front end lifted and lowered just fine. After I shut the engine down, there was a loud hissing sound from the front equipment compartment. I swung the door open and looked inside, but could not identify the source of the air before it stopped. I tried raising the rear again and again, it wouldn't budge and after shutdown, after a minute or so a loud hiss came from the front control valve area. I finally gave up and called it a night, with a poor level condition.

The next morning, I started the engine and within a few minutes tried again. This time it worked! The rear end lifted about 8 inches and once again, we were up. All systems OK.

I know how to prevent the problem, i.e. don't raise the tag. Once before, on pavement when I had used the tag lift prior to parking that the coach sat low in the rear. I remember shutting down and going outside when, after several minutes I heard a creak and saw the tag axle move in the corner of my eye.

So, it seems to me that I have a problem not with lifting but with lowering the tag back to ride height. Not having seen the mechanism I don't know exactly how it works. Do the airbags on the gag depressurize when you lift the tag? Do the lifting bellows simply let the air out to drop the tag? Are the tag suspension air bags supposed to auto-fill as soon as the tag is dropped?

Or, am I simply misusing the tag function?

-fred

I'll try to keep it short. This is only a guess so don't run off for repairs until you can verify it.

When you lift the tag a three port Norgren valve located on the upper frame between the tag and drive axles (both sides, 2 valves) closes the air flow between the drive axle air bags and the tag air bags and exhausts air in the tag axle air bags so the axle can be lifted.

I am trying to remember your coach (which was over my pit at one time) and I think when your steering wheel is at the extreme either left or right, unknown to you the tag also has the air in its air bags dumped automatically to facilitate turning. That makes lifting the tag unnecessary.

I think what happened was the three port Norgrens failed to close, likely due to the third three port Norgren located on the passenger side aft of the tag axle up on the frame failing to shift. While you were trying to raise the rear, you were doing it with only two air bags per side instead of three. You would not hear air escaping because it was already exhauseted from the air bags on the tag.

At some point however the pilot valve decided to function and the two 3 port Norgrens opened the path between the drive axle air bags and the tag air bags and your coach operated normally.

I have posted before the worst thing that can happen to our coaches is to fail to exercise them. They were build for many miles of service and a lot of the components function better if used regularly. The Norgren valves certainly fit that description. My guess is as you use the coach occasional anomolies like this will show up but as you continue to exercise the systems the little annoyances will just go away. Having said that, recognize the Norgren valves have a life like most things mechanical. They have O rings that can begin to leak and their polished interior can start to corrode if exposed to moisture over time. The moisture comes from an air system that has not been maintained.

On my coach, needed or not I pulled my Norgren valves out at their 10 year point and just replaced them all. When the coach hits 20 years of age the same thing will happen because I have experienced all the things associated with aged valves, air bags, brake chambers, etc. so I am just going to avoid as many of the annoyances as possible.

My advice, lift your tag, play with your suspension, do all the normal things you do and do not worry about it. If it happens again, put the level low controls in the road position or the manual position and keep cycling it through various positions until the valve decides to function again. I really doubt if you will see a repear.

BTW, it could be attributed to a single solenoid or solenoid valve in the 5 valve mainfold on the rear bulkhead of the steer compartment. But if it is, worry not, because the only valve in that stack that is critical is the center one which controls the ride height valves. As long as that one functions you will go to ride height and be able to drive.