Community Forums

dansawyer · 10-22-2022, 08:02 AM

The MH is a 2002 Nat'l Tradewinds on a Spartan chassis. New front tires were installed about a month ago and I have noticed a 1 to 2 inch list to the passenger side. Before I start 'fixing' the leveling system is there a way to determine which axel it is? I thought if I lifted the front with the single piston lift and it 'leveled' then it is reasonable to assume it is the front. Is this a bad assumption? Is there a better way?

Ray,IN · 10-22-2022, 02:44 PM

That is not a reasonable way to determine ride height, which is the source of your "listing".
Spartan has a specific measurement for each wheel position, for each chassis model. Ride height should be in your Spartan chassis manual for your year and model chassis. For instance; I have a 1999 Spartan Mountain Master GT chassis with independent front suspension. MY alternate front ride height is 16 and 1/8" measured from bolt centers of each shock. I forget rear ride height measurement.
Spartan main measurements are from bottom of frame to centerline of axle_I think.

A positve way to find out is call Spartan customer service with your chassis VIN in hand.

Dutch Star Don · 10-22-2022, 08:52 PM

You have three ride height valves creating a triangle leveling system. Some coaches use two in the front and one in the rear like my Monaco. My Freightliner uses two in the rear and one in the front. It sounds like your Spartan uses two in the rear and one in the front. The front SINGLE valve can't make the coach list to the right or left, so if it's a ride height issue, it has to be one of the rears.

Did they move any tires around on the rear when you had the two new tires installed on the front? Sometimes, some of these guys will accidently lift the coach in the rear and catch the right height arm and bend it.

dansawyer · 10-23-2022, 10:28 AM

Thank you. No, there was no rotations. I suspicion is the mechanism was disturbed during the replacement process. I was looking a starting point to diagnose if this was new with the tire change or if I had just noticed iit. I will next inspect the sensor mechanism and measure the height.

It will be a few days, we are starting a 2000 miles trip. Dan

Ray,IN · 10-23-2022, 11:30 AM

Spartan uses Neway ride height valves (2) in the front like this: https://www.truckspring.com/products..._90054007.aspx
The linkage rod is a universal fit, available at any truck repair shop or truck stop repair shop. The linkage rod in the video is right of where he is working with a rubber adjustment held to the correct length by small radiator clamps.

This utube video shows them and replacement procedure.
DO NOT ATTEMPT THIS WITHOUT BLOCKING UNDER THE FRAME OR ON A HOIST!

https://www.youtube.com/watch?v=IGwT1xMhonI

dansawyer · 10-24-2022, 05:55 AM

Thank you. I will follow that link. My first step was to figure out if something was wrong, I am now convinced there is. On flat ground the right side is definitely lower by 1/2 to 5/8 inch. Ride height is a totally new area so I was looking for the vocabulary and parts indentification as starting points. This will help get that process started. More later, Dan

dansawyer · 10-28-2022, 10:04 PM

Update: The first issue does not appear to be ride height adjustment.

First: The issue appears to be a 'weak' passenger side rear air bag. Taking the pressure off the front with the front leveling hydrolic jacks does nothing to level the coach. However leveling the rear with the passenger leveling jack levels the front as well.

Second: There appears to be an air leak somewhere. The main pressure (rear) drops to 50 lbs after 4 hours. The secondary remains up much longer. (This is new, 6 months ago it stayed up for 12 plus hours.)

Is there a thread on diagnosing air leaks?

Is there a thread on testing the air bag itself?

Ray,IN · 10-28-2022, 10:57 PM

Both your questions are answered by using a spray bottle with a high-sudsing soap and water mixture, or kids bubble soap.
Spray every compressed air connection, each air spring, and tank fitting, then observe for bubbles.
Exercise caution while underneath to avoid getting trapped or crushed should the system lose air pressure.

The tanks should each have a manual water drain valve, pull each one and observe for water and/or oil being expelled.
Spartan's MM chassis has a 3rd compressed air tank just forward of the rear axle specifically to supply compressed air to the rear air springs. This tank only has a radiator-type petcock for a drain, as all moisture should have already been removed by tank #1 up front alongside tank #2.

dansawyer · 10-29-2022, 08:28 AM

Thank you. If I read the chart correctly:
1. The secondary tank provides air the the Norgren valve.
2. The Norgren valve supplies air to relay valve, rear susp.
3. The relay valve supplies air to the rear leveling valve.

4. The rear leveling valve supplies air to the Acc Tank, rear susp.

5. The Acc Tank, reas susp supplies air to both rear air susp bags.
I do not see any controls between the output of the leveling valve and the actual air bags. I will start by:
A. looking for leaks
B. testing / exercising the rear bags by manually exercising the rear leveling valve. (carefully !!)

Am I missing anything? Thanks Dan

rvspec · 10-29-2022, 08:46 AM

An air bag wont affect ride height unless if has a leak that the compressor can't keep up with, very rare. Air pressure sets ride height. Chassis with ride height sensors on the front axle that are out of adjustment can cause the opposite tire to over loaded, a very dangerous situation. if the air bags are original or show a lot of cracking they need to be replaced. It is a problem you don't want on the highway.

dansawyer · 10-29-2022, 12:28 PM

Thank you. I am trying to diagnose one of three condtions before I make any changes:

1. The left front leveler is too high.

2. The right front leveler is too low or weak.

3. The right rear leveler system is weak.

I am leaning toward the 3rd.

a. When I raise the front with the jack system the right rear is still low. The front is a single hydrolic system and when raised should remove any front torque from the rear. i.e. this should remove the left front leveler from the equation.

b. When I level the rear by using only the right rear jack the front levels out.

This leads me to a right rear problem. I am planning on soap bubble testing this weekend.

Is there an error in this logic?
Am I missing something?

Thanks, Dan

twinboat · 10-29-2022, 04:24 PM

The error is that the levelers have nothing to do with ride height. When you lift the front, the leveler valves will let out air of the air bags to attempt to maintain the proper height.

The air bags don't get weak ! Like a tire, they hold air or not. Like a tire, let air out, tire goes down.

If you have 2 ride height valves in front. One is set to high or the other is set to low. Same thing if there are 2 in the rear.

The valves add or let air out of the bags to keep the RV at ride height all of the time . It's an active system.

If you weight 500 lbs and get in the RV side door, the RV will sink slightly. Once it sinks, the ride height valves opens to add air to that sides air bag to pick it back up. Jump back out and the valve let's some air out so it's not to high.
I hope this makes sense to you.

dansawyer · 10-31-2022, 09:43 AM

Update: Diagnosis journey
Yes. Leveling jacks and ride height are separate systems. However they can interact. Leveling is a 3 point system with common front and separate rear controls per wheel. Ride height is also a 3 point system with separate front controls per wheel and common rear via the rear air bags.

The vehicle is on level ground. I have raised the front slightly with the jacks to remove most of the pressure from the front air bags. The rear ride height is still pressured up.

If the rear bags are working properly the rear should be level side to side. It is not. Additionally I have measured the inflated height of the rear bags.

The left rear bag measures just over 10 inches. The right bag measures just under 9 1/2. I believe the cause of the 'list' is the rear bags are not inflating evenly.

eman588 · 01-21-2023, 06:20 PM

Quote:

Originally Posted by dansawyer

Update: Diagnosis journey
Yes. Leveling jacks and ride height are separate systems. However they can interact. Leveling is a 3 point system with common front and separate rear controls per wheel. Ride height is also a 3 point system with separate front controls per wheel and common rear via the rear air bags.

The vehicle is on level ground. I have raised the front slightly with the jacks to remove most of the pressure from the front air bags. The rear ride height is still pressured up.

If the rear bags are working properly the rear should be level side to side. It is not. Additionally I have measured the inflated height of the rear bags.

The left rear bag measures just over 10 inches. The right bag measures just under 9 1/2. I believe the cause of the 'list' is the rear bags are not inflating evenly.

Responded to one of your other posts on air leak. I’m experience this same levelling issue end of last season. I think the rear on the left side on mine is down as well. I’m planning to change air bags, really cause they are 20 years old and got cracks. The trick finding replacement airbags.