Stands

[gmcbuffalo]

I have been replacing the air bags in the rear of my bus and I have the bus up on Jon's stands. The other day I was working under it sit behind the differential when the for some reason I heard and felt air coming out of the one Norgren (I think the top one) and all three bags on the drivers side went empty. PANIC. But the bus didn't drop because of the stands. You never know what may cause the suspension to drop.

I could understand why the tags would dump air if the pressure got low, but all three bags on one side? The passenger side three bags were still rock hard. The bus is level on the stands so I don't think it has anything to do with the road leveling controls. Level selector was in Drive and the key was off.

[garyde]

That is Scary but its great to know when your safe from such a failure. Will you replace the norgren?

[dreamchasers]

I have been replacing the air bags in the rear of my bus and I have the bus up on Jon's stands. The other day I was working under it sit behind the differential when the for some reason I heard and felt air coming out of the one Norgren (I think the top one) and all three bags on the drivers side went empty. PANIC. But the bus didn't drop because of the stands. You never know what may cause the suspension to drop.

I could understand why the tags would dump air if the pressure got low, but all three bags on one side? The passenger side three bags were still rock hard. The bus is level on the stands so I don't think it has anything to do with the road leveling controls. Level selector was in Drive and the key was off.

Very interesting!

If you heard air escaping from one of the five port Norgren mounted on the forward bulkhead, in front of the differential, during this deflation of the airbags, then the Norgren either intermittently failed or the pilot valve in the pneumatic cabinet failed or gave the signal to the Norgren to dump the air. I am one that believes the Norgren valves used in our busses are very high integrity valves. If you look up the specification, the number of cycles are rated in the thousands (can't remember the exact number). Far greater than the usual RV owner will ever cycle the valves. The biggest issue I have found is that after many years of operation in the hostile environment under the bus, the o'rings will shrink and leaks will occur.

Concerning the leak, if your Prevost is of the vintage that when low aux pressure results in a tag axle release, then their will be a momentary lose of air pressure. But it should not have deflated the air bags completely?

The best thing is you had you bus sitting on Jon's jack stands. I use mine anytime I crawl under the bus, every time! I carry mine in the rig. Of all the tools I have acquired for the rig, the jack stands are rated at the top of the list. Jon should get the POG "Safety Award", if we have one, at Austin.

Thanks Jon for taking the time and effort to build the Jack Stands!!!

Hector

[johnklopp]

Jon,

I was missed out getting a set of stands from your last production run. Are you willing to consider another production run if enough of us are interested? OR, will you sell a set of drawings that could be taken to a welding shop for fabrication?

John

[gmcbuffalo]

Can these Norgrens shuttles be serviced without taking the Norgren body off the frame?

[BrianE]

I recently replaced all of the under-chassis Norgren valves in our 98/99 Royale. The bus has always been garaged but lived in the south for the first 10 years of its life. I found all of the valves badly corroded and the O rings brittle. One of the front Norgrens had failed internally. Norgrens are a simple, all aluminum spool type valve with very little to go wrong. Corrosion and age however can be their downfall.

Thanks Jon, for your suggestions and warnings in reference to changing rubber dependent components around the 10 year mark. Preventative maintenance starts at home where it's a lot cheaper and more convenient to get done than on the road.

Greg, Norgrens can be overhauled but in my opinion its more trouble than its worth. I can't imagine you could do so without removing them from the coach. They can be purchased locally but the savings was minimal.

[Jon Wehrenberg]

I consider Hector the auxiliary air genius of POG. I will add my 2 cents to this discussion and hope he jumps in here.

Low aux pressure should not result in air dumping on one side (I don't think). If my theory is correct it may be that the loss of aux pressure allowed the Norgren on one side to dump air, but the other side for whatever reason did not shift due to the low pressure. If might be because the Norgen internals are not moving smoothly and as Brian pointed out could be corroded.

I did rebuild my Norgren's on the first bus, but it is soooo much easier just replacing with new. Corrosion internally will mandate a new valve because the rebuilt valve with internal corrosion will never function satisfactorily.

[dreamchasers]

Greg,

As Brian mentioned, its seems simpler to replace the entire valve when needed, thus assuring all components are new. A comment worth mentioning, when reinstalling the pneumatic fittings into the new Norgren valve assembly, take extra precautions to assure you use thread sealant to assure you do don't create minor leaks in the fitting connection. Jon has stated that he prefers using a liquid thread sealant and has good experiences with it. I have used Teflon tape for many years in industry on connections involving hydrocarbons gases with success. I think both type of sealant work satisfactorily.

Let us know what you found leaking? With the complicated suspension systems and aux air systems on our coaches, any knowledge of potential leaks spots is a benefit.

Good Luck.

Hector

[gmcbuffalo]

I noticed this one sided thing after changing the bags and thought it had something to due with the ride height valve. It does it even with good Aux air Pressure. Yesterday the drivers side was deflated and the Passenger side Up. So I dropped the aux air down to 20 PSI and waited about 5 minutes later the Passenger side tag dumped. So I think I have a bad Norgren. Mine are almost welded to the frame I could not get them off when I was changing the bag without the thought of damaging them. Maybe I did. Those tubes in and out are so short and ridge I thought the best way was to take them off. No way. A year ago I changed the air dryer who know when and if it was done before. So replacement sounds like the best option.

[Jon Wehrenberg]

When replacing a Norgren you obviously need to do a leak check on the fittings. But I have learned that I can save myself a lot of grief if I bench check the new valve before I install it.

I just used a bunch of fittings that I could thread into the new valve on my workbench and apply air pressure at the various points to verify the new valve will work and is leak free. Should the new valve have even a minor leak it drives you crazy trying to sort out why the bus leans or loses air, especially when all the fittings on the bus to the valve are leak free. If you are just replacing one valve it is less frustrating because you can zero in on that one valve, but if you are changing out all the valves at once it eliminates the risk of having to figure out why the bus with new valves is still leaning or losing air.

As to keeping the air system dry, that is a little bit of preventive maintenance that pays huge dividends. The cost to change dryer elements every year or two (I use two year intervals) and to drain all the tanks every time you get under the coach keeps the inside of the Norgrens clean, shiny and dry and eliminates many problems due to moisture. I know of at least two coach owners whose poor air system maintenance resulted in a Norgren having a hydraulic lock which makes diagnosis of any problem much more difficult.