Coach listing to one side?

Topic: Coach listing to one side? (Read 608 times) previous topic - next topic

Coach listing to one side?

May 17, 2021, 03:34:35 pm

After following behind the wife's car in our '98 U295, she mentioned that in the rearview mirror the coach appeared to be listing to one side. On flat and level ground a tape measure shows the left front corner (driver side) to be sitting 1" lower than the right. The left rear corner measures 1/2" lower than the right.

I took measurements of the airbags. Without a caliper I couldn't straight-line measure so I had to bend a tape measure around the bags, but at least I got numbers for comparison. The measurements are from top of top plate to bottom of bottom plate.

For all I know the coach has been like this since I bought it last summer, and we never noticed. Or it's something new. Either way, what advice can I get from this group as to how serious this is, and what I should do about it. We were/are planning to leave on a 6,000 mile coast to coast and back trip next week.

Coach front
   Right airbags
      Forward 9.5"
      Back 10
   Left airbags
      Forward 8.75"
      Back 9.25

Coach rear
   Right airbags
      Forward 8.85"
      Back 9.0
   Left airbags
      Forward 8.75"
      Back 9.125

Re: Coach listing to one side?

Reply #1 – May 17, 2021, 03:41:08 pm

Plate to plate should be 8 1/2 inches from bottom to top of bottom plate.

Re: Coach listing to one side?

Reply #2 – May 17, 2021, 04:02:27 pm

dan and annie
I assume your coach was aired up and at ride height when you
measured. an easy way to get an exact measurement is between
the frames behind the front wheels and in front of the rear wheels.
that measurement should be 8 inches.
I carry an 8 inch piece of wood that I use to occasionally check my
ride height.
remember to block the coach if you adjust the front ride height valve.

Re: Coach listing to one side?

Reply #3 – May 17, 2021, 04:13:35 pm

You can make a caliper out of a piece of plywood.

Re: Coach listing to one side?

Reply #4 – May 17, 2021, 04:31:46 pm

You are in luck, simple problem to fix on that coach. The ride height sensors just needs to be adjusted add or remove air in the bags to get the correct heights.

It is possible that a valve is bad but both times I had a valve go bad the bag would loose all of it's air and had to do the manual adjustment until I replace them.

Re: Coach listing to one side?

Reply #5 – May 17, 2021, 04:36:07 pm

How do I go about adjusting the ride height? A couple of people have already mentioned ride height valves and sensors. How do I do this?

Re: Coach listing to one side?

Reply #6 – May 17, 2021, 04:41:15 pm

The bottom of the rod that works the ride height valve is threaded. Make the rod longer to raise ride height/shorter to lower it.

Be on level ground.

Have air pressure up, then turn engine off.

Measure at the bags toward the CENTER of the coach (front bags on back axle/back bags on front axle).

Do rears first.

Then with the single ride height valve in front, "average left/right

Re: Coach listing to one side?

Reply #7 – May 17, 2021, 04:46:54 pm

You have three ride height valves two on the rear of the coach and one in the front between the bags. You will see a rod going through a rubber boot on the ride height valve. If you go to the search and type in ride height or air bag there are lots of posts on the subject.

Re: Coach listing to one side?

Reply #8 – May 17, 2021, 05:30:04 pm

Ride Height Adjustment [ForeForums Foretravel Motorcoach Wiki]

Re: Coach listing to one side?

Reply #9 – May 17, 2021, 05:34:07 pm

Yup, the two "where do I measure" CAN be confusing:

From the link (and correct):

To measure the ride height one must choose one of two measurements.

Measure from the top of the top plate to the bottom of the bottom plate, which should be 8.5 inches

-OR-

Measure from the top of the bottom plate (where the bag sits on the plate) to the bottom of the top plate (where the plate sits on the bag), which should be 8 inches.

Adjust the two rear height adjustments first. This should give them the correct height and the side to side measurement should be the same. Then adjust the single ride height for the front.

Re: Coach listing to one side?

Reply #10 – May 17, 2021, 05:55:59 pm

https://www.heightcontrolvalve.com/docs/Meritor-Wabco/HCV-Tech-Bulletin.pdf

Re: Coach listing to one side?

Reply #11 – May 17, 2021, 08:30:39 pm

Thanks for all the help here. I think I'm ready tomorrow to get under there and see what I can do. It may be just looking around and identifying parts, because my driveway is crushed stone and shell, i.e. not flat and level. I don't even have a flat surface to take a measurement from, so when I do the work I'll have to find a parking lot somewhere.
Question: When I'm adjusting the valves, I assume I'm under there with the safety blocks in place, at least for the front valve. So when I play with the valves, is the air system be active, adding and subtracting air to the bags while I'm doing this?

Re: Coach listing to one side?

Reply #12 – May 17, 2021, 08:42:50 pm

You can't have safety blocks installed as it stops you from making adjustments. Drive up on some boards in the front, the back can be reached from the outside. Or take measurements when you are on level ground and do the math on what the front needs. Raise and install blocks and trial and error adjustments until you get it right.

Re: Coach listing to one side?

Reply #13 – May 17, 2021, 08:56:01 pm

Dan,

It's a trial and error process. For each height control valve, you must decide which direction it needs to be "adjusted". Say the left rear corner needs to come UP a little bit. You get under the coach (safety stands in place) and slide the vertical linkage rod a little bit in the direction it needs to go to ADD some air to that corner. After that, you have to remove the stands, let the coach drop down to ride height, and see how it looks. I know - it sounds like a tedious process, but usually doesn't take too many tries to get it dialed in.

Remember, on the rear of the coach, that raising one side will cause the other side to lower a bit. Sometimes, when you think one side is too low it is really being caused by the other side being too high.

You might not be able to get the front exactly level side-to-side, but you should be able to get close.

One of our members (I think it was Don IIRC) made some safety stands that supported his coach at the correct ride height rather than being raised all the way up. With the shorter stands in place he could play with the height control valves until he found the "neutral" position on all three valves. Then he raised the coach up all the way, removed the safety stands, and the coach returned to the correct ride height. Pretty clever! See if you can follow his explanation:

More on ride height???

Re: Coach listing to one side?

Reply #14 – May 18, 2021, 08:06:44 am

As said, you should be able to both measure and adjust the rears without crawling under the coach.

And, the tool I use is a scrap of quarter round about 12" long. Then drill and install two long thin nails exactly 8.5" apart.

They should be used to measure "beam to beam"= top of top air bag mounting plate to bottom of bottom plate.

I find this dimension easier to measure than 8" "bag dimension"= top of bottom plate to bottom of top plate.

Then with coach still on the ground, determine what you need to do in front, and either use safety stands in front or have the front up on 2X 12" so even if the air bags completely deflate you have safety room. Part of that dimension (how many boards you need) depends on YOUR "thickness".

Re: Coach listing to one side?

Reply #15 – May 18, 2021, 09:44:48 am

High Tech Ride Height Measuring Device (HTRHMD)
jor

Re: Coach listing to one side?

Reply #16 – May 18, 2021, 09:45:59 am

Quote from: jor – May 18, 2021, 09:44:48 am

High Tech Ride Height Measuring Device (HTRHMD)
jor

Yup, that's the one.

Re: Coach listing to one side?

Reply #17 – May 18, 2021, 09:50:32 am

Looks good Jor,only thing I would do different is grind the points off the nails so I would'nt stick it in the air bag.

Re: Coach listing to one side?

Reply #18 – May 18, 2021, 09:53:10 am

Quote from: John44 – May 18, 2021, 09:50:32 am

Looks good Jor,only thing I would do different is grind the points off the nails so I would'nt stick it in the air bag.

If 8.5", they do not go where the air bags are, but above and below the plates supporting the air bags. Basically "beam to beam" dimension.

Re: Coach listing to one side?

Reply #19 – May 18, 2021, 02:52:11 pm

So when you drive the front onto 2x12 boards do you have to have the rears on boards as well??

Re: Coach listing to one side?

Reply #20 – May 18, 2021, 02:57:57 pm

Quote from: dicksop – May 18, 2021, 02:52:11 pm

So when you drive the front onto 2x12 boards do you have to have the rears on boards as well??

No the ride height valves will seek the same number with front and rear different heights. Think climbing a hill same difference.

Re: Coach listing to one side?

Reply #21 – May 18, 2021, 03:09:38 pm

Quote from: dicksop – May 18, 2021, 02:52:11 pm

So when you drive the front onto 2x12 boards do you have to have the rears on boards as well??

A good question. Never tried to check with coach front higher than rear. I guess theoretical it could put the front rear set of bags at a slightly different dimension than the front front set air bags.

Re: Coach listing to one side?

Reply #22 – May 18, 2021, 06:15:02 pm

Quote from: dicksop – May 18, 2021, 02:52:11 pm

So when you drive the front onto 2x12 boards do you have to have the rears on boards as well??

Based on what Brett said in post #6, I would say yes.

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