Water in air system/air-bag size

[ajhaig]

We stopped by Prevost in Mira Loma, CA to have our front ride height checked (the front mud flap was dragging when we made sharp turns at slow speeds).

It turned out that the ride height was only slightly below spec (our front mud flap is lower than it should be) but they were unable to adjust the fitting because of a faulty valve. Additionally, there was some clear water in the front air tank, no water in the rear tanks. New valve, air dryer filter and we are back in business.

The conclusion was that our aux air pump, which has been running frequently (about 2 hrs/day, in 10 min. intervals) was introducing water into the air system and that water caused the front leveling valve to malfunction. Has anyone experienced this before?

Also, it was suggested that since Marathons of our vintage tend to be front heavy, we should consider upgrading our front air-bags to larger ones. Our front air bags are only 3 months old. Has anyone upgraded to larger air-bags & should we consider doing this?

Many thanks.

AJ

[Jon Wehrenberg]

AJ....Prevost made the retrofit to larger air bags in the early 90s. Apparently yours did not get them. I cannot remember the details, but I do not think any welding or modifications were involved. If you contact Prevost parts in Elgin they can answer your questions about what may be involved. I think the newer air bags were referred to as Mae Wests at the time.

The cost should be 2 hours labor and about $290 for the two air bags. If your current air bags are only 3 months old (and they will have a label with the date on them to show a buyer that) offer them to any POG member at a price fair to both of you.

A general comment about the aux air pump and water. We have discussed on this forum that if a coach owner relies a lot on the aux air compressor the aux system needs a "spitter" or water trap immediately downstream from the aux compressor so water can be caught and drained before it gets into the aux air system. People who full time in the coach would be the typical owner that could be in need of this spitter.

The consequences of water in the aux system, especially introduced from the front can be very substantial. There are at least 4 solenoid valves and several Norgren valves that will get screwed up if they get filled with water, and they will.

Joe C. has lanyards and valves on the bottom of his air tanks and I would urge that those get added (I hope Joe jumps in here) to the wet tank in the rear, and the aux tanks in the front to keep the system dry.

If you get water in the system and it freezes all sorts of bad stuff can happen.

[Kevin Erion]

AJ,
Steve at California Coach has the upgraded air bags on his early Marathon, give him a call.
Kevin

[Joe Cannarozzi]

Once again for the recent arrivals to the group.

My Bus 057.jpg

My Bus 053.jpg

Those air bags are not interchangeable with any in the rear? Just curious. How many different styles are there on one bus anyway, 4?

Or are their some common ones from one position to the next.

[Jon Wehrenberg]

The ones on AJ's front now are interchangeable with his tags.

[Joe Cannarozzi]

I got a dirty little secret for you Jon.

The last time we had ours up at Central States Charter I had them look at the front end and try to find out why we keep breaking the eyelets off of the front shocks.

Well, that is when I found out that they put a little too much camber in the front axle on the early XL's and hence the adjustable radius rods to correct that.

I was also informed that our front air bags are one new style and one old

The bus doesn't know any better, the driver can't feel it, and they are both recent replacements.

[lewpopp]

AJ,

I had Mae Wests put on our 90 about 4 years ago. as I can recall ( wow), I think it was about $500. I have a heavy Marathon and I put larger tires on the front also a couple years ago.

[Jon Wehrenberg]

Joe,

Actually the bus does know the difference.

It is all about air pressure. The air springs or air bags as we call them are inflated until they raise the coach up to the ride height based on the adjustment of the ride height valve. Once the ride height valve arm reaches the neutral position no more air is introduced to the air bags.

So if you have two different size air bags on the front axle, they will both have the same air pressure because they are tied together. The air bag with the larger size will lift more weight at a given pressure than the smaller one, so it will tend to lift up that side of the coach a greater amount.

If you do nothing to compensate for that your coach will lean towards the small bag side. Depending on the difference in size of the small versus the large bag the lean can be great or barely perceptible. But let's presume you decided to check your coach ride height and fine tune its adjustments. To zero out that lean you adjust the side with the lean in the rear and raise it up a little and with the exception of having higher air bag pressures on one side compared to the other you will never notice it. But your coach will go down the road with a constant extra lifting force at one rear corner. It doesn't mean diddly, but it is there.

Lew's coach has a heavy front end and where the bigger air bags help him is that without them his originals could barely lift the front end. Once the front end came up to the correct height it was probably OK, but those original air bags probably took every pound of pressure his air compressor could generate to lift the True Value Hardware store.

[phorner]

You're right on about the Hardware Store.

I needed a left-handed metric rivet driver the other day and darned if Lew didn't have one....

[Joe Cannarozzi]

Agreed. I considered that but decided it was O/K to run it, steer axle weight barley 12000. I'm guessin that is the same conclusion that the Eagles Nest came to when they put it on. I'm pretty sure that's who dun it and they been fixin buses for years

The folks at Central States also concurred. I'll get it strait, eventually.