Air ride

[Keith Moffett]

I freely admit that in my persuit of repairs before things break down, I sometimes see problems that dont exist.  This may be one of those.
When we got this coach the air ride seemed real solid while traveling.  I barely noticed bad road.  Now it bounces three or four times on the front and the air pressure is down to 90 lbs or so.  It also seems to take longer and longer to recover.
Interestingly the same problem exists in the brakes.  Months ago it seemed I used the brakes while manuvering several times and lost 10 - 15 lbs.  The other day while parking the coach in a tight spot the air alarm went off and it took several minutes to rebuild.
All that said, we often park and just leave the air up.  We dont have air leveling just ride.  Never the less it goes two days losing only 10 lbs or so one time and next time it will be down to 90 lbs over night.

What do you all think?  Ride height valve?  Air can?  How does one check an air can?  Anyone use those air flow control valves on the air bags?

Thanks
Keith

[Lee Welbanks]

Keith,

The ride bounce usually means shocks but I guess it could be the air suspension losing air. The air loose and recovery sounds like you have a big leak somewhere. Build up the air to compressor cut out and shut off the motor get out and listen and see if you can hear air leaking, if not then apply the service brakes (pedal) and have somebody listen around for air escaping. With all the air systems on these things it could be anywhere.

[Dave Atherton]

Keith, the first question is your air system building up to 120 PSI and than hearing air dryer pop off.
Second question, when you pull yellow button out, to apply parking brake does the air at valve ( one
yellow button is pulled ) seems like the air takes longer to stop hissing sound. Third air pumped up and
air dryer poped off, with engine shut off does the pressure gauge on dash go down and is it more than
( 1 ) pound per minute. The answer to above questions will tell a person if you have a problem or not.

The first question you have to have min 120 PSI when air dryer pops off, answer should be yes.
Second question applying park brake  ( pulling Yellow Button out ) hissing sound is longer than normal.
answer  be no, if answer is yes you have a pancake bad on your spring brake on rear axle.
third question with air supply pumped up and air dryer pops off at 120 Psi, watch pressure gauge on
dash if needles are going down more than ( 1 ) pound per minute.   this will give a idea if there is
something going on with vehicle air system. Dave Atherton Retired Cat Mechanic

[Steve Huber Co-Admin]

Keith,
If you have the original Bilstein shocks and around 75K miles or so on the coach, the shocks are probably bad, causing the "porposing". I recently replaced mine with Konis at 93K. The Konis give a good ride but IMHO, not improved enough to justify the added cost compared to the Bilsteins. Shock Warehouse has some fairly good prices and free shipping.
Steve
S

[Keith Moffett]

Keith,
If you have the original Bilstein shocks and around 75K miles or so on the coach, the shocks are probably bad, causing the "porposing". I recently replaced mine with Konis at 93K. The Konis give a good ride but IMHO, not improved enough to justify the added cost compared to the Bilsteins. Shock Warehouse has some fairly good prices and free shipping.
Steve
S

Steve, are you saying that if the shocks are bad the travel on the air ride valve is using more air when hitting a bump?
I have looked at Koni and am not convinced either considering the cost!  What physical indicator shows a shock to be bad?
Thanks
Keith

[David T. Richelderfer]

http://www.motoringabout.com/when-to-replace-shock-absorbers/

and I would augment these with a seventh item...  when a shock absorber is leaking oil.

[Keith Moffett]

Keith, the first question is your air system building up to 120 PSI and than hearing air dryer pop off.
Second question, when you pull yellow button out, to apply parking brake does the air at valve ( one
yellow button is pulled ) seems like the air takes longer to stop hissing sound. Third air pumped up and
air dryer poped off, with engine shut off does the pressure gauge on dash go down and is it more than
( 1 ) pound per minute. The answer to above questions will tell a person if you have a problem or

Dave
The air drier was rebuilt last year with a kit.  It does build to 120 and the over pressure release valve activates but not as noticable as it was before rebuilding.
When applying the park brake there is very little air release with the button, just a quick 'cht' sound.
With the air ride at full pressure and the engine off the guage might show a small loss over night.
thanks
Keith

[Keith Moffett]

David
I appreciate the input.  Over the years I have come to believe I know some things about mechanics.  Working on these MH's things are a bit different. I usualy find t better to confirm what I believe I know to be true.

I do have some diving on curves and vibration through the steering wheel and ratteling noise on rough roads.  That said, the air ride may be minimizing a shock problem so it hasnt been as noticable as it might have been.
I am not so sure that this can account for greater air loss on rough roads and longer recovery times.

Keith

[Steve Huber Co-Admin]

Keith,
Sometimes you might see oil leaking but my experience has been ride quality. When it starts bouncing or shaking, shocks are normally the chief culprit and with 75-100K miles, you've gotten your $ out of them anyway. Might be that air system but from your ride symptoms, I'd put shocks at the top of the  suspect list.
Steve

[Dave Atherton]

Gentleman, with Keith first posting I half way agree with the bounce going with shocks worn or
bad. However where My thoughts going down the road with only 90 PSI showing on air pressure
gauge tells me there is a problem within the air system. Pressure should be running 120 PSI in the
Air system and air tanks. With the rear spring brakes locking up wheel at 50 PSI and system pressure
at 90 PSI only few pumps  on brake pedal and your out of air before spring brakes apply.
( Note the rear brake chamber one for each wheel have a big spring inside of brake housing and is
Released with air pressure you build up  pushing yellow button and unlocking each wheel.) wheels
with release at 60 PSI . Keith you mentioned loosing 10 to 15 PSI just applying brakes than the light
came on. Sounds like air governor needs adjustment. But my first post my first question what is your
pressure on gauge in cab.  Dave Atherton Retired Cat Mechanic

[Edward Buker]

Dave and Keith,

The suspension in these coaches use a lot of air while traveling and my air gauge cycles between about 90lbs and 115lbs about every 20 seconds to perhaps a minute depending on the tilt of the road, wind, and bumps. It cycles back quickly at road rpm, so although we use a lot of air, the recovery rate is quick due to the relatively small size of the reservoir tanks when compared to the air quantity being used. I have done leak down tests and the air system is good.

The issue with the alarm when braking multiple times while idling and maneuvering is you can use more air then is being generated at low rpms. That is normal and is a driver awareness that needs to be monitored. I was thinking that the coaches were set up for 90 to 115lbs possibly for a reason so I have not messed with mine. I have never thought of the 90lb cut in pressure as any problem. Wondering if 90lbs to 115lbs is normal for most of us with this chassis?

Even with a change to 100 to 125lbs things will not change much regarding how much air we use and our reserve while driving, braking, at idle speed.

Later Ed

[Dave Atherton]

Ed, we both agree air pressure needs  to recover and maintain 120 psi, point of concern many air
systems  slow to recover can present problems. Been involved in many out of service ( vehicle Tagged
out of service, air compressor slow recover and air pressure bleed off with engine shut off that exceeds
more than 1 pound per minute.) there is a standard that pertains all vehicle with air systems with D.O.T.
When we worked on air systems that standard,had to be followed. when I see post with air systems
something is out of place means Safety. In most states, motorhomes drivers are exempt from having a B class
( air brake endorsement ) driver license but it is clearly spelled out. Our mechanics  were required to have air brake
inspector endorsement including myself working repairs with on road trucks. We had to sign off on
repairs that fell in line with D.O.T. Reg's. Anything to do with air systems cause for a big concern to myself.
Dave Atherton Retired Cat Mechanic

[Edward Buker]

Dave,

I was not implying that an air system should not be leak free to a standard. I would not be happy with one pound per minute leak down and mine is tested periodically by me and surely does better than that. The pressure build time at idle with a tight leak free system is such that you can use more air feathering the brakes and rocking while rolling in a campground then can be generated at idle. Just a fact of life the driver needs to be aware of. I do not know if 90 to 115 is right or 100 to 125psi is better. We should see what others have and debate that one a little maybe.

Later Ed

[Lee Welbanks]

With mine I  have never seen the gauge pressure change much going down a road, even with curves ànd rolling  bumps. Air pressure will hold for two or three days if leveling is turned off.. I do have a leak in the rear on the leveling system I will find when we get home in a week.
System cut in 92 cut out 121 psi.

[Jerry Emert]

My cutin seems to be about 100, cutout 120.  I don't see any variation in the air gauge while driving down the road.  When I first bought the coach I noticed an "air" light flashing on the dash when bouncing over bridges and such.  Haven't seen that in over a year though, no idea what it was.