How long should an RTS hold air?

[Eric]

hello again! My an440 seems to only hold air after and hour or so of shutdown...i've taken my handy dandy bubble solution and haven't found any serious leaks! my air bags are new (and Yes i checked em!) and most of the lines i've either replaced or @ least removed and tefloned...my biggest problem is I would like to keep the doors shut on their own! I asked the local bus garage (midwest kearny NE) and they didn't seem to think it's a big deal. I don't think it's right is it?

Thanks Guys!

[buswarrior]

If you are trying to keep the air up, any and all leaks need to be stopped.

No such thing as a less than serious leak in that arena.

Check the exhaust ports of all the brake valves very carefully, they are regular culprits.

And the exterior of the leveling valves.

happy coaching!
buswarrior

[Dallas]

By the way,

This is an AN440:



And this is an RTS:


They are different critters from different mamas. 

[DaveG]

How much air does it leak in an hour...if you shut down with full reservoir pressure, what is the pressure after an hour?

I'm with your garage, I don't think it is much of an issue, an inconvienence maybe, to be sure.

Air leaks can be difficult to cure, since probably they have been accumulating for years (before you got the coach) and now you are trying to fix/cure years of defered maintenance.

One thing to do is listen for them, so you'll need it to be really quiet when you're chasing them down. The other is the soapy water test. Another, as already said, is the exhaust ports of relay valves. Don't forget the safety factor of being under the bus when the bags go flat....

Another method is system isolation. In other words, isolate a specific system and see if the leak goes away or the loss changes. This may require disabling the air ride system or another system....you get the idea.

If you want more ideas, let me know.

Dave G

[NJT5047]

Keep in mind that walking around in an aired up bus causes the leveling valves to constantly adjust the airbags which bleeds off air. 
My thoughts would be to forget maintaining an aired coach for more than a few hours.   That just isn't likely to happen on a geriatric bus.   
Figure out some way to lock the doors mechanically.   Or create an RV door of some sort.   
I'm agreeing with your garage on this one.   
The cost/benefit ratio doesn't support trying repair an air system to a point that will maintain an aired up coach for--say--24 hours.   A new truck will hold air for days, but most buses leak down to the point that the doors won't self-seal after a few hours.   
JR



 

[TomC]

This is really sort of funny with my bus.  Sometimes, the air will stay put and the bus will stay up for over a week.  Other times, it will be down to near zero pressure and the air suspension totally down (I have new air bags).  Can't explain it.  Good Luck, TomC

[Sojourner]

All air ride buses have 3 (4 if is front dump equips) ride height levelers. If any of them leveler lack of any viscosity fluid or none...it will cause an instant respond to add or exhaust air until it at adjusted height. Whenever a windy day or getting in/out of coach whiles it not driven will cause to use up the air supply till it to low to refill.

You can test it by having someone of about 200 pounds standing on the first step while the other person listen for air exhausting on the rear/driver side. If it exhausts instantly...means it low viscosity fluid or otherwise you have to wait at least 4 second before exhausting which is normal. Do the same thing to test the right side with 200 pounds onto somewhere to cause the coach to lean downward at the driver side.

Most buses have 2 rear air leveler and 1 front leveler. Never more than 3 levelers except the front end dump version.

Sojourn for Christ, Gerald

[Eric]

Thanks Guys! time to play monkey some more!

[Chopper Scott]

My MC 7 leaks down in an hour or so. It really is just an inconvenience but I hope to somewhat remedy that situation with new bags and leveling valves this winter. Kearney Nebraska? I live in Holdrege ekhedge!! Only 30 miles away. I knew there were a lot of nuts out here, just not so many bus nuts  . Later

[NJT5047]

Changing the airbags (even nice looking airbags may ooze a little air), leveling valves, brake chamber diaphrams, all flex hoses, all regulators, air dryer disharge valve, treadle valve, any (all) door control valves and cylinders, AC and blower tensioners,  any air system component with a check valve or diaphram, wiper controls and motors, and air compressor gov will begin to reign in the leaks.   
On a brighter note, kits to rebuild most air systems are not expensive.   
Regarding failing leveling valves...locate the various leveling valves and pull off the short exhaust hose from the leveling valve.  The exhaust hoses may be rotted off and just a fitting left. 
Install a several foot long piece of appropriately sized hose onto the leveling valve exhaust and place the other end of the hose in a clear container of water.  If you see continuous bubble from the exhaust port, you got a bad leveling valve.   If anyone heavy enough walks over the area controlled by the valve you are checking, it will discharge air after they move away from the area.  As Gerald says, on a windy day, the bus could rock enough to add to the air discharge.   
This little test will rule out leaks in the leveling valve mechanism.   It will not ID loose fittings or such.
A good spray-on leak detector (and cheap) that will ID loose fittings and valves is WalMart children's bubble solution.  It'll grow nice big'uns. 
Christie Hicks offered that tip some years ago. 
What you'll often find in air leaks is a slight seepage times however many components you have.   
A good many leaks are moving thru exhaust ports at a very low volume and are hard to detect...brakes for instance.   
Another nice item is a leak detector..but they are expensive.   
Often children, especially females, can hear things that most males will miss.  They might be able to locate more obvious leaks. 
Air leaks are a nightmare to sort out on an old coach.   Difficult to locate.  Checking some components for leaks will be almost impossible.
That said, there is clearly some value to resolving as many leaks as one's budget can stand.  Some air leaks can be traced to brake flex hoses and diaphrams which obviously should be promptly repaired.   
ONE more thing...if you have DD3 brake chambers, they can be safely (relatively) disassembled for repair.  If you have spring brakes...those units are dangerous to dink with.  The return spring must be caged when disassembled.    Servicing spring brakes will hurt you. 
If you have to apply the service brakes when setting the park brake, you probably have DD3s.   If you pull out a yellow knob and the park brakes set, you have spring brakes.   


Good luck, JR