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-   -   Droopy Rear End (Motorhome) (http://www.airforums.com/forums/f159/droopy-rear-end-motorhome-9041.html)

smily 01-27-2004 07:14 AM

Droopy Rear End (Motorhome)
 
The rear end on the driver side of my 1990, 33' LY leans low in the rear of the coach. It is very obvious.

My air system seems to be working okay and holding pressure.

I may have a slow leak in rear bags but I have not determined that. I have replaced the front Airbags with new ones. The front Airbags are independant of the air compressor system. You add air individually to the front Airbags via dedicated hoses.

The rear end sits low even with air system fully charged and the compressor has stopped running. (should the compressor come on everytime I start the MH?)

I suspect something is awry with the rear suspension.

Any thoughts on this?

Smily:confused:

wb13798 01-27-2004 07:29 AM

sound like you have two leveling valves. if so it isnt a big deal . just adjust one to mach the other. is that the stolen motor home???

smily 01-27-2004 07:40 AM

Location
 
Where are the valves?

Smily

thenewkid64 01-27-2004 07:45 AM

The best way to find the valves is to look at the bottom edge of the rear axle, normally next to the bags. There will be a rod that goes up toward the floor. The valve will be at the top of this rod. I have the same issue since I replaced by bags so I am going to have to spend some time on my back checking the fittings and lines. I may just have one that is a bit loose. While you are under there it is a good time to inspect the bags themselves. Look for cracking or flaking. If you see either you may need to get them on the list for replacement. Replace them in pairs.

smily 01-27-2004 07:52 AM

Compressor cycle
 
Should the bags hold pressure all of the time or do they bleed down when the compressor is not running?
Why does my compressor come on at cold start and run for about 4 minutes prior to shutting off?

It may be cycling during driving but I cannot hear it if there is cycling.

My pressure guage seems to indicate that there is around 120 pounds while running down the road. I say 120lbs but may be off. It indicates in the green area, (good).

Smily

87MH 01-27-2004 08:00 AM

Is there a tag axel?
 
Ken,

On the tag axel classics the air bag sensors are on the trailing arms of the torque rod to wheel axel assembly. One on either side.

Easy logic, since the tag axel is completely independent of the air bag suspension, if the tag axel wheels get too close to the underbody of the coach, the leveling controls think "hey, the tag axel is carrying too much weight", and send more air to the bags so the main drive axel takes more weight. Conversly, if the tag axel wheels are too far away from the under floor (too much angle in the tag suspension), the sensors think"hey, got to add more weight to the tag suspension", and bleed air from the bags, allowing the coach to settle down, putting more weight on the tag axel wheels.

Hope this helps.

smily 01-27-2004 08:06 AM

Huh?
 
Yes there is a tag axle

So what are you saying?

Are you implying that the Tag axle sensors are either bad or not working properly?

If so, what does the sensor look like? can you get a replacement?
Is is electronic? If so what does it talk to, valve, compressor,.......?

Smily:confused:

87MH 01-27-2004 08:08 AM

My pressure guage seems to indicate that there is around 120 pounds while running dow
 
Ken,

That is good. The compressors are single stage, and that (120 psi) is about the upper limit for single stage air compression.

If you are carrying 120 psi in the volume tank, I would say you would have to look downstream from there for any problems.

As far as the suspension system bleeding off during non-use, on the Xeppelin, that is normal. Whenever I put down the rear jacks, and take a little weight off of the rear suspension, the tags develope a bit more ositive angle, and, according to my previous post, proceed to dump air from the bags in an attemto to bring the tags up to their "normal" level. Of course, with the jacks down, this can't happen. So, for me, a transfer of air from the volume tank to the air bags is normal whenever I come down off of the jacks.

Right now, I do not know what pressure is normally in the bags at my usual road weight.

Interesting question, I'll post after getting a bag pressure readout.

87MH 01-27-2004 08:19 AM

Sensors
 
1 Attachment(s)
Ken,

The sensors are simple pneumatic devices (on the Xeppelin, anyway), the early 80's single axels suspension used solenoid controls. On most of the 80's era air streams, the coltrol arms can be quickly identified, just look for anything with an incredably bad weld job on the control arms. Just look under the coach. They will be easy to spot.

smily 01-27-2004 08:22 AM

Not the same situation
 
My compressor runs even if I have not deployed jacks.

I am asking if the bags bleed down everytime you shut off engine.

Or, are they supposed to maintain last pressure rating prior to shutoff.

Am I making any sense?

Smily

smily 01-27-2004 08:29 AM

Valves
 
Thanks for the depiction.

I have a valve on the passenger side just rear of the tag axle that protrudes from the bottom of the side panels.

It has a shrader valve and a cutoff valve . I opened this cutoff valve once, (briefly) and air escaped the valve. I immediately closed it.

There is not a valve on the driver side of the coach.

I have been wondering what this valve is for. It appeared to be a method for adding air to the system but apparently it is for releasing air. (I guess)

Smily

87MH 01-27-2004 08:32 AM

I am asking if the bags bleed down everytime you shut off engine.
 
Ken:

The answer to your question is definitely "no".

Once the system is static, under normal circumstances, there should be no transfer of air either into or out of the bags. As stated earlier, once the leveling sensors adjust to the proper angle, they have done their job, and everything should remain pressured up.

If you think the system is bleeding down quickly, you should be able to hear the air leaking off after shutdown, and a leak that large would be easy to locate.

As part of the troubleshooting, I would recommend getting an accurate weight on all three of the axels. At least that would tell you if the tag axel is carrying too much weight (bag or sensor problem), or not enough (torsion axel rubber problem in the tag).

On edit......or, worst case scenario, the whole thing is overloaded and there is just too much weight in the rear overhang for the suspension to compensate.

smily 01-27-2004 08:37 AM

Thanks
 
I have listened for leaks and nothing obvious but I will get under vehicle and check a little closer.

The only indication I have of any bleeding is the fact that my compressor comes on everytime I start vehicle. It runs for about 3 to 4 minutes before shutting off. Is this normal?

I realize I may be asking the same question more than once, bear with me.
I am used to giving answers not questions.

Smily:D

87MH 01-27-2004 08:47 AM

Good Question
 
"The only indication I have of any bleeding is the fact that my compressor comes on everytime I start vehicle. It runs for about 3 to 4 minutes before shutting off. Is this normal?"

Ken,

Don't know.

The PO put a HUGE compressor in. The compressor is mounted all the way to the rear of the coach, under the bed. I can't hear if it comes on or not from the drivers seat, it is that quiet.

I can tell you, that since getting the electricals to it straightened out (too small of a wire feeding the motor), unless I lower the rear jacks to the point that the sensors dump the bag air, (I can hear the air bleeding, but I know this is normal), my air system does not bleed off.

The Xeppelin does not have an air pressure guage, only an idiot light mounted in the dash, but the light has not come on since upgrading the feed wire, and the air suspension brings itself to normal (usually) as soon as I get down off of the jacks. On rare occasion it takes a slight movement (forward motion of the vehicles length) for the air sensors to pick up the change and compensate.


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