[Richard]

In a weird coincidence, I spent all day working on my front HCV. And I learned a WHOLE lot that may help you when you work on this.

I don't readily know the answer to your issue, but let me talk about the things I learned today.

When I first saw the setup, I was certain that someone had done a hack job on installation of the HCV. The reaction arm was way too short in my opinon. I thought that would make the valve too sensitive to up and down movement and waste air.

I was wrong. Newell mounts the lower part of the vertical rod to the sway bar in my case. The valve is hard mounted to an arm welded to the frame. So the movement is actually the rotation of the sway bar. Unless the mount on the sway bar extended all the way to the axle center line, which it does not, the movement is actually much less than the movement between the tires and the frame.

So the way this is compensated is the reaction arm is shortened.

All of that to tell you this. The length of the reaction arm has a tremendous impact on the dead zone. The dead zone being the hysteresis in the vlalve action. If I raised the coach and then put in travel it settles to one ride height. If I lower the coach and let it raise it settles to a lower height. Drum roll. If the reaction arm was five inches there was 7 inches difference between the two heights. If the reaction are were shortened to 3 inches the difference in the two heights was about 2.5 inches. I shortened the reaction arm to about 2 inches and the difference heights was right at 3/4 inch. So, if you get to fiddling with this valve be aware of this situation.

It gets even better. With the reaction arm so short any movement of the up and down rod is exaggerated. 1/4 inch of adjustment in the up and down rod made 1 1/4 inch difference in ride height. Be aware that very small adjustments make a huge difference in ride height. This is completely different than at the rear where it is virtually linear, move the adjustment rod the amount you want to change the ride height.

To your particular problem. I suspect either a problem with the internals of the HCV or a leak between the HCV and the six pack.

A quick diagnostic may help. If you lowered the coach below ride height and put it in level, do you still hear air? If you do, then you have a leak between the HCV and the six pack. Here's why. The HCV always has supply pressure, and if the coach is low the valve is actually trying to raise it, but since the output goes to the six pack travel solenoids, that air path is effectively blocked at the six pack, but it would be pressurized.

You stated that that if you raise the coach and turn on Leveling that the air hiss stops. That tells you the air line into the HCV is not leaking, since the air line into the HCV is always pressurized whether you are in travel or level.

The valve could be defective in that it is trying to raise and exhaust air at the same time. Having taken an HCV valve apart this morning, I can see two things that would cause that. Debris, or broken internal parts of course. Also, if you have the valve that Michael pictured, if you remove the rubber boot on the bottom, then the felt filter, you will see a white cylinder with a screw in the middle. Turning the screw clockwise increase the dead band in the valve, or in other words a half turn inward may get you out of the raise and lower simultaneously mode until you get a new valve.

I can't say without really observing your coach, that your concern about it not coming back to correct ride height is part of the problem. Or its that issue I talked about earlier where the coach will reach different ride heights depending on whether is settles down to ride height or it raises to ride height.

Gee I hope that makes sense and helps.

You have my number.