4104 Leveling problem

[T Chellis]

Hi guys,
I know this has been talked about before but please humor me.
I have sealed off the air beam in the front driver side with the fancy alluminum plates on the bellows and isolated that part and checked for leaks and is ok. Problem! Front driver side still settles down. Now I am looking at the leveling valve. Before I block up the beast and get underneath Should I check the air filters on the leveling valve first, or figure on replacing the the leveling valve or I don't know? Tell me this, am I headed the correct way in trying to solve this sinking problem. It is just that corner that seems to be a problem.  Thanks in advance for your info.   T. Chellis

[RJ]

T -

Problem is quite possibly the REAR leveling valves.

All the front valve does is control the ride height at the front.

The two at the rear control not only the rear ride height, but also the left/right vertical orientation.  Driver's side might be set too low, passenger side set too high, driver's side has slow leak, etc.

From what I understand, it's also far less time-consuming and frustrating to simply replace the leveling valve rather than try to rebuild them, if you find a leaky one.

Time to get out the soapy water again!

FWIW & HTH. . .

[zubzub]

I haven't had this problem, but as soon as the levelling valves start to give me problems I will probably remove them and use a manual system that allows me to set the ride height.  Might seem like a lot of trouble but I know from sleeping on the road that getting the rig level is important for a good night's sleep.  Also once you know the pressure of a given ride height with a given load ( you'll need gages) you will have a level bus.  Seems to me that as the levelling valves were set up to keep things level under an ever changing load, you could also make the installation of a levelling system much simpler by bypassing the levellers completly. 

[tekebird]

keep in mind..the leveling valves are an integral part of the ride comfort and quality.

a manual single PSI system will make the ride harsher

[jjrbus]

I put a manual system on my bus and it is a bit harsher ride, but barely noticable. You can keep the over the road sytem and add a manual system for when parked or do away with the original system. It is neither hard nor expensive to buy or make a manual system.
                                                                                 HTH Jim

[zubzub]

Forgive my ignorance, but if the manual system allows me to set the pressure of the bags how is that different from the levellers?  Also re manual system seems a great extra benifit that if I ever bottomed out the body (or was getting close) I could temporarily lift the bus a little.

[tekebird]

the OEM leveling valves are in a constant state of adjusting the air preasure in the bus to provide a level and smooth ride this is not only dictated by the load in the bus but also the road surface, crown, bank etc.

as for bottoming the bus out.........I hope you do not intend/plan on doing this...it is not hard NOT to bottom the bus out if you are paying attention to where you and the bus are.

From the Stock ride Ht I doubt you will gain anything in Ht enough to get you off a high center or other grounding

[PP]

I have a three valve manual over-ride that allows me to adjust the front height on one valve and the rear left and right on two more valves for leveling up when she's parked. This works great for getting a good night's sleep. But when you fire up the beast, the auto leveling system takes over just like Tekebird describes in his last comment. When I'm parked for any lenght of time, I plug my little aircompressor in line with the regulator set at 100PSI and it maintains my level indefinitely and only comes on for a few minutes every day.

[JackConrad]

     When we added our manual system, we kept the OEM leveling valves. The OEM valves still operate when driving and we switch to the manual valves when parked to level the bus. The OEM valves do not actually level the bus, but maintain an equal distance between the body and axle (if the road is leaning, the bus will be leaning). On one occasion, we had to drive through a mud hole in a gate opening to get out of a camping area after a hard rain during the night. Before starting to move, I aired up the bus to the maximum height and dumped the air in the tags to put more weight on the drive axle. We made it, BARELY!.  After getting through the mud hole we went back to look at it. We could see where our oil pan had drug in the mud.  Would we have made it without lifting the body ??  (no way of knowing)  Jack

[zubzub]

my point exactly, if your having fun, sometimes you need a little extra lift.  Regarding the levelling valves, I had understood they didn't cycle that often( ie., no twith every bump in the road) so I still don't get why they would make the ride smoother than the ride height  adjusted to spec with man., valves.

[tekebird]

yes they don not cycle with ever nook in the road but mine cycle walking around the bus as well as getting on and off the bus.

do a bench test on a leveling valve and hook it to a air source and cycle the lever.

the difference may not be percevable my some but we have already had a post with someone who did the manual only mod with his bus with real life before/after commentary.

[T Chellis]

Thanks for everyone's comments. It is very helpful. I never thought about the leveling valve in the rear effecting the front.  Time to get out the bubble bath and start crawling... T. Chellis

[buswarrior]

Not mentioned: suspension geometry.

The whole thing is supposed to be kept in a certain relationship between body, axle and wheels.

Change the ride height, there may unintended consequences?

happy coaching!
buswarrior

[Sam 4106]

Hi Guys,
I think there are some errors in some of the thinking going on in this thread. If you eliminate the height control valves (some incorrectly call them leveling valves) and install manual valves, you can not achieve consistent height by setting the pressure in your gagues to a predetermined value. It takes a certain pressure to start raising the bus. After the bus starts to raise it only takes more air volume, plus a little more pressure to overcome friction, to continue to raise the bus. I have had my manual system in for 15 years and can't get a consistent height just going by pressure. However, by removing the height control valves it eliminated suspension leaks. In my opinion, the best system would be to have a seperate manual or automatic system for campground leveling and the original height control valves for on the road use.

I agree with zubzub and Jack that being able to raise or lower the bus height can be an advantage. While converting our 4106 I had to deflate the suspension system in order to get the bus into the shop I had then. I have also found it useful to fully raise the bus at times, Twice going into driveways the hitch hung us up ( I have since changed the height of the hitch) and once we got hung up in the middle going over a railroad track. Our 4106 has 7" of travel between a completely deflated suspension and fully inflated suspension on the rear. A little less on the front. I find that to be very useful.

Good luck, Sam 4106

[RJ]

Not mentioned: suspension geometry.

The whole thing is supposed to be kept in a certain relationship between body, axle and wheels.

Change the ride height, there may unintended consequences?

happy coaching!
buswarrior

Buswarrior makes an important point.

When I was at our local transit property, we had a driver who constantly complained about a shimmy in the front end of the 1977 Flxible New Look he was assigned to drive.  The shimmy always took place between 35 - 45 mph, common speeds on our major streets.  The bus was rotated to other drivers, who also made similar comments.  Shop put on new, balanced tires - same complaint.  Pulled wheels/tires, did a complete brake job on front, including new wheel bearings, reinstalled balanced wheel/tires - same complaint.  Replaced shocks - same complaint, said ride was better, but still shimmied.  Pulled front end apart, installed new king pin bushings and all new tie-rod ends - still shimmied.  Shop was beginning to think the driver was nuts.  Funny thing, tho: he never voiced this complaint when assigned other buses, so Ops knew it was something with the coach itself.

Finally, one night while the coach was over the pit having it's brake adjustment checked, the tire guy was down there also, visually checking the inside of the tires.  While looking at the front end, he just happened to notice that the lever between the front leveling valve and the linkage to the axle was bent slightly.  Knowing that this was the "possessed" bus, he pointed it out to the mechanic who was adjusting the brakes, and suggested that they check to see if the front ride height was set to specs. . .

You guessed it - it was off!  As a matter of fact, it was off so much that the front end was literally at it's maximum height, which meant that the two air bellows were inflated so much that there was virtually no suspension travel to the front end.  (This model coach has four bellows on the rear, and two on the front.)  With little or no suspension travel, the irregularities in the roadway while running at about 40 mph would set up an oscillation in the front axle, which was then transmitted into the body of the coach as a shimmy, apparently.  After several thousand dollars worth of unneeded front end work, the whole problem was solved by simply replacing a $10 bent lever and setting the ride height to specs.

Moral to the story:  For highway operation, it's hard to beat the factory engineers.

Moral to the story for RV busnuts:  Keep it factory for the highway, isolate the leveling valves for a manual system in the campground.  Tie an audible alarm into the system so that it reminds you to change over when you release the parking brake.

FWIW & HTH. . .