re: Adjusting Height Control Valves

[gpatom]

Well here I am again needing help. I have just install 3 new height control valves and am having a problem getting them adjusted evenly. Does anyone know someone in the Victorville, Ca. area that may have some knowledge on air suspension that I may talk to. I just can't get the bags to air up evenly. Either one raises to high before the other raises and then will exhaust the air before the other bag inflates. I have my manual on how to adjust them but I can't seem to get it done. I have also replace the pressure protection valve to the aux. tank. I have tested for air leaks. Just can't get them to fill evenly. I did mange to get them to fill evenly by using the leveling jacks but they would not hold. HELP PLEASE!!! If someone can even call me on this my phone number is 760-949-7615 or my cell # 760-953-5034 it would be greatly appreciated. Oh yeah, I have the '87 Neoplan Metroliner.
Thanks,
Tom

[TomC]

The best way I found is to jack up the bus with blocks under the tires high enough so when the bus air bags are fully deflated you can still be under the bus with plenty of room.  When you make an adjustment, the best thing to do is to disconnect the connecting rod to the axle and manually deflate the bag all the way down.  Then reconnect it and see where it settles.  You can make small adjustments that are more accurate this way.  Granted it might take an hour or so, but then they are adjusted.  Trying to adjust it a little up and a little down, just doesn't work since it changes once you start driving.  That's the reason for deflating all the way down so you can get an accurate measurement from where the valve will stop the travel.  Remember-don't get under your bus unless you have enough room for you when the bags are all the way down, or else you'll be crushed!  Good Luck, TomC

[gpatom]

Hey Tom C, Thanx for the reply. I have tried letting all the air out of the bags and then setting the control in neutral position and refilling the bags and making the adjustments as stated, but the passenger side will fill to set position before the driver side does, so as the driver side fills  the passenger side starts to exhaust do to overfilling causing the driver side to stop filling. Are they supposed to both fill at the same rate at the same time? I jacked the coach up and got them at the right level but then they would not hold. Don't have any leaks but just can't find the problem. I know a lot about a lot of things but this air suspension really has me baffled as I have no experience with it before. Any more suggestions? Need all the help I can get!!
Thanks,   Tom H.

[H3Jim]

Does it ever find equlibrium where none of the valves is exhausting or filling?  Is it near level then?

[gpatom]

Jim, Tom will get back with you in about 1hr. or less to answer your question. One of his friends needed his help. I don't know the answer.  Thanks, Mrs. Tom H.

[gpatom]

Jim, I can remove all the connecting rods and then set the bus absolutely level and then set all three valves in a neutral position and then reconnect the rods and then when I deflate the bags and refill them they still will not come up level.
Tom H.

[Sean]

Tom,

The valves on your Neoplan take quite a while to settle.  And, yes, because the front suspension is fully independent, you will notice the bag on one side might come up before the other side, then have to come down a bit as the other side comes up, due to the geometry of the A-arms.

In order to properly adjust these, you need to have the coach on perfectly level ground, air up fully, and let it sit for at least five minutes for the bags to settle.  If you have any air leaks at all in your coach system, you should leave the engine running during this process to ensure a good supply of air pressure.

Once the coach settles, measure your ride height clearance at each corner.   Adjust the rods one at a time, again giving the coach at least three full minutes to settle between each adjustment.  I suggest you adjust the two front arms first, getting a good left/right adjustment, since usually the fronts are closest to the supply air and will fill faster (on my Neoplan, the rear takes a few minutes longer to come up than the front).  Once you have the left/right done, adjust the rear until it's level front/back.  Remember, you are filling/emptying four bags in the back (if you have a three-axle coach -- two bags if a two-axle coach) through one valve, whereas in the front you are only filling/emptying one bag with each valve.  So it will take longer for the bags to catch up with your control arm.

Remember that each adjustment will also cause changes in the other bags, so you may need to adjust each rod two, three, or even four times, making smaller and smaller adjustments each time, until it's right.  And you'll need to wait three to five minutes in between each adjustment.

Now here's the worst part -- lock all the rods at these settings, then drive the coach around the block.  You will find things have changed, because the tire contact patches were not in the "right" places when you started.  Moving the coach will have relaxed the tensions created by the tire contact points, and you will now need to adjust everything again.

Oh, and make sure that the last thing you did before stopping to adjust things was to drive *forward* at least a bus-length.  If you back up, you will put a different set of stresses on the running gear which, again, will change the way the bags sit.

Let me know how it comes out after spending a couple hours running through this whole process.  If it still won't settle down, you may have either an air leak someplace, or a constriction in one of the lines.

-Sean
(Who just rebuilt one of his ride-height valves yesterday due to crud on the piston.)
http://ourodyssey.blogspot.com

[H3Jim]

Just a few random thoughts...

Are the new valves the correct replacement part?  Leveling valves are generally a pretty simple affair.

It sounds like you are saying that once a valve starts to exhaust, it doesn't stop until the bag is deflated?.

Mine work completly from the control rod.  If the rod is up, it inflates, if down it deflates. As the bag inflates, the bus rises, the rod lowers a little since its attached to the frame.  Air stops moving when the control rods  are all level.   Neutral rod position is  horizontal. Neutral, air is neither inflating or deflating, and the bus is level.

while generally, mine pump up at about the same rate  if they are down, it does not matter to much since each one seeks that level rod position.  When the rods are level, if they have been adjusted ccorrectly, the bus is level.

Did you install the new ones just like the old ones came out?  Did you take pictures before disassembly?

[gpatom]

Again Thanks to all of you fellas. I have received some good input. Sean I did not do all those things you suggested but I will try it. It could be I did not allow enough time for the bags to settle and I never tried driving it in between the adjustments. Jim yes mine work similar to yours also. Pete it was really good of you to call and I liked your suggestion. I am going to try Sean's suggestion first because that seems like the easiest place to start. Anyway I Thank all of you and I am sure one of these will work for me.

Tom H.