You are not logged in or registered. Please login or register to use the full functionality of this board...

Leveling System Condundrum
Looking at the graphs again, a thought occurred to me (scary isn't it). In both the bottom 2 graphs it looks like the coach ended up at about the same height. Perhaps others can chime in. If the drive axle air is locked in with none added or released and you release the tag axle air, how much does the coach drop?
Jon Kabbe
1993 coach 337 with Civic towed

This is a follow-up to the original post. First of all thanks for all the input. It was very helpful and allowed me to learn much more about my leveling system. And as with most of my stories, the result is a good news / bad news scenario. (My brother says there is no bad is only how I choose to handle it :/)

The good news is that the problem has gone away. The bad news is the problem has gone away without a complete understanding about where it went.

Since I first posted this thread, I did two things that may have affected the answer. First, I replaced all the height control valves. I also replaced the differential lockup valve. The HCVs were original to the coach (2003 with 240000 miles), and I just wanted to replace them for general purposes. The diff lockup solenoid valve was replaced because it would randomly start venting air (lots of air) for no apparent reason. the valve body was mounted with the exhaust up and this allowed grit to enter the valve.

With these two changes, I cannot replicate the coach just sitting down in the back with the key off and auto-level off.

My gut feeling is that the problem was related to the diff-lockup solenoid. I am thinking that when it decided to vent all the air out of the system for some reason, the rear airbags decided to play along and also deflate. There is no good reason to think this...but when I heard the diff lockup solenoid start leaking, it sounded just like the few times I was where I could hear the bags deflate. (Remember this was not a slow leak, but a rapid deflation).

So, the question I am left with is ... What could cause the rear air bags to deflate (left and right) when 1) Key off, auto level off 2) No air in the system 3) Coach is something less than travel height in back?

I will continue to try to isolate the issue and will report back if I develop new information.

Thanks again for the help!

ps. I don't know if I said this before, but I could not cause the issue when plugged into shop air.
Bill Johnson
2003 Newell #653 Quad Slide Cat C-12 engine with Motorcycle lift 
2011 Jeep Wrangler, 2018 BMW 1200GS Adventure Motorcycle
Auburn, Alabama
Here are some observations (not as scientific as Bill’s) about my coach and leveling. Over the past 2 years when I stop, put slides out and level either auto or manual by releasing air, and leaving in auto level, within hours to days the coach would work down to a pancake. Recently by accident, I figured out that if I manually raise the rear first then auto level, the coach is rock solid for days. Does this indicate that some valve is worn at or below ride height in the rear? If so, which one?
Mike & Jeannie Ginn
2000 Newell #555
2013 Chevy Avalanche
(09-10-2017, 01:27 PM)bikestuff Wrote: Gurus,

I have had a weird leveling related issue for a while.  One of the senior gurus reminded me that collecting data is a valid way of isolating problems and identifying the likely cause.  This post is to document the data collected on my coach.  I present a problem and an approach to troubleshoot but not an answer.  (Because I have not figured it out yet).  

In a nutshell, the issue is that if I leave the coach in travel mode at full travel height, the coach stays level and does not leak down.  However, If my air bags are somewhat below travel height, they will leak rapidly down in the rear of the coach.  (For example if I auto level, or turn tightly where the HCV has let air out on one side, ...).

I have attached a document with three graphs of data collected over the past couple of days....The coach was parked on a reasonably level pad.  Measurements were made at the bottom of the body panels behind front wheels and the bottom of the body panels in front of drive wheels.

Three tests were run:

No Auto Level (travel mode).  The coach was put into travel mode and measurements taken over a 36 hour period.  

Auto Level On -> Off .  The coach started at travel height, and was then auto leveled.  Auto level was then turned off and measurements taken after 2 hours.

Travel -> Dump Air (No Auto Level) -> Off .  The coach started at travel height.  Air was dumped using the leveling system for 8 seconds.  Then the HWH was turned off.  Measurement was taken after 4 hours.


1)  The coach does not leak much in level mode with the bags full.
2)  Auto-level results in the coach dropped in the rear.
3). If I partially deflate the bags using the dump valve, the coach will continue leaking down to the bottom.  (This is with the key off and with auto level turned off).   
4)  With the key off and auto level off, the coach should maintain its height, but does not. 
5) The leak appears to be in the rear air system.
6)  When the leak is present, both the left and right rear air bags seem to track each other.  
7)  The leak down is not related to the auto-re-level logic because auto level was turned off in each scenario.

Next steps....  
1) Adjust the mercury switch so that auto-level results in an initially level coach.  I will do this by using a 4 ft level to manually level the coach, then will zero out the mercury switch.
2)  Since the problem seems to be related to the amount of air in the bags, I will replace the HCVs.  My HCVs are original in the coach and I really just want to replace them for general purposes.  I will try the tests again with new HCVs.  In the meantime, I will use my isolation tool to try to isolate any leaks to the 6 pack solenoids or downstream air bags.
3) I will also repeat scenario 2 (partial air in bags) and see if I can detect a leak with my sonic leak detector.

Hello Bill, I fought the same issue for a while but it was on the right side. I Have a Valid system and the 6 pack block is HWH. I disconnected the main input to the block and blew the block and line out. it helped and was able to get it to raise. it was like I had something caught in the system. we don't leave here for a week or so and I'll know it was fixed. fingers crossed.
Ron Gripon
2003 coach 660-F150 
2005 Porsche Boxster
Bill just a thought but a bad ground makes weird things happen when you have some or all valves daisy chained from one to another.
jim hit on something here. all of us have had erratic grounds cause problems in different systems in the coach.

i was having erratic readings on my dash and ran dedicated grounds to some of the gauges.

2002 45'8" Newell Coach 608  Series 60 DDEC4/Allison World 6 Speed HD4000MH

Forum Jump:

Users browsing this thread: 1 Guest(s)