I got those (air) leaky bus blues

[plyonsMC9]

Hello busnuts,

The diagnosis on my leaking air from the rear of the bus came back from the mechanic as follows:

[the mechanic] has repeatedly sprayed soapy water on the air springs, height control valves, lines and fittings.  The leveling valves and check valves are new, so air shouldn't be back feeding through them.  By the process of elimination, the air must be leaking through rust pin holes in the tops of the air beams, at the floor level where you can't test it. 

Could there be anything else?  Or, does this seem like the way to go?  It would be great if I could pinpoint the cause of that leak as I have been trying to find it for some time now.   Someday, I'll be able to use air levelers.  I just know I will. 

The fix:  install bypass plates on the 4 rear air springs :  $1,208

Doesn't that change the ride?  I think I've read in other threads that it makes the ride rougher.  Is that correct?

thanks folks!

Kind Regards, Phil

[rdbishop]

Hey Phil, You would think that by now someone would have come up with something we could spray up ilnto the beams. Maybe something rubber like or like undercoating or something......Richard

[Sojourner]

One of the common problem of MCI's air beam.....after years of moisture soaked accumulated road dirt or salt eating the top of beam's plate (about ¼" thick new) to change to flaky rust. If you repair via weld up all pin hole or holes...you will lightly end up bigger hole until reach pure steel to weld to. I replace my front beam's top with new ¼" steel.
However using "block plate" you will decrease cubit displacement area of spring cushioning effect greatly. Equal harsher ride over "uneven patched" bump or ripple dirt road.
Rolling lobe is the best choice for the quickest repair to maintain the smooth ride nearly of original air beam system. Combine air beam & rolling lobe would be the softest ride over harshest bump but not available on market with 1 ¼" hole air passage on top of rolling lobe.
The difference between "bellow" type to "rolling lobe"; (you can experiment with toy balloon)
1) A bellow type is like a balloon in between 2 large books to compress.
2) A rolling lobe is a balloon in between 1 book on bottom and blunt end object such as "light bulb" push into top of balloon to "roll-in" to achieve more vertical travel before burst.

MCI's parts replacement for older buses link;
http://www.mcicoach.net/assets/featureProducts-Sept2005.pdf on page F24

There maybe other brands....any one here?

PS...liquid sealer won't do because air beam does not rotate to spread the sealant around & rusty flake will eventually loosen more later.

FWIW

Sojourn for Christ, Jerry

[Stan]

You indicate that you still don't know what is leaking. You have to isolate and test individual sections to find the culprit. There is no point in plating the beams if the leak is a faulty new leveling valve that is leaking back into the supply tank.

[DavidInWilmNC]

It might not be all that difficult to pull up the carpet (or whatever) in the rear of the bus and cut out a piece of the plywood to check the beams.  I took up the entire back or the floor on my '8 and was surprised at the good condition of my air beams.  I did clean out the insulation, scrape, paint them, and seal around them, but they werent' all that bad.  I removed the rusty metal sheets that cover the fiberglass wheel wells and replaced that with galvanized.  Most of the moisture in that area on my bus was from the windows leaking and water running down (judging by the piece of rotten plywood).  I've got the leaky bus blues too, but mine are water leaks.  Depending on the layout of the rear area of your bus, you might be able to pull up the entire floor in that area, fix any rust, insulate, and put down new plywood.  It's really not that difficult to pull that wood up, just don't hit yourself in the face with a 3' pry bar like I did doing it!  Even if you do seal the beams, it seems like whatever moisture that's getting in there would be causing mold, etc.  Also, there is a small removable plate in the passenger side rear bay that leads into the area where the air beams are.  If you have the same, you might be able to get a light in there and use a mirror to inspect the area.  I'm planning on leaving that cover off so the area will breath a bit and hopefully prevent future moisture issues.  Good luck with it.

David

[JackConrad]

Road dust can work its way into the area on top of the air beams. Add moisture from rain or condensation and you have the start of rusting. If I was going th change to blocking plates OR rolling lobe air bags, I would go with the rolling lobe. Our MC-8 had block off plates on the rear when we bought it. I changed to rolling lobe airbags and could not believe the difference. The ride was so much better.  Jack

[plyonsMC9]

Just spoke with the shop - they said they had not had the problems if only the rear beams were plated since the weight of the bus was so considerable at that area.  The result was that the ride not noticeably harsher.  They will quote me for the rollling lobes - no problem - but it is more $$.  The shop also said they don't do the plates on the front beam due to the harshness.

My follow up question is : Has anyone blocked of just the rear beam and had a harsh ride?  Thoughts?

Thanks folks!!!   

[JackConrad]

We have a road near our place that had a lot of small holes filled, so we then had a lot of small bumps. With the block off plates, I always tried to miss as many of the bumps as I could. After installing the rolling lobe airbags, I found myself looking for bumps to see how much smoother the ride was.  Our rolling lobe air bags came from Mohawk Industries.  Jack

[jjrbus]

I'm not sure on the 9 but on the MCI5C there is only 1 line going to each air beam. It would not be that hard to unhook that line. Then make up an adaptor with an air fill and install in air beam, a pressure gauge could be included. Or use the bellows as an indicator. Pressureize beam with this setup and if it leaks you would be 98% certan it is the beam!

[edroelle]

I agree with Jack.  Correct the problem and install rolling lobe air bags.  I was never satisfied with the ride after regular bags were plated.

Also, a friend who use to be on the boards, had his air beams repaired with new metal.    The job was done by a professional and looked VERY good $$$.  A short time later, they were leaking again.  So, after all that, he THEN added the rolling lobe bags.   

The air beams were just a bad design because of the corrosion.  If most of your air beams are not leaking yet, it is only a matter of time before they do.

Ed Roelle
Flint, MI

[Stan]

http://www.busconversions.com/bbs/index.php?topic=3206.30

I put this post on a few weeks ago as a method to isolate air leaks in suspensions. Paying a mechanic to go around with a spray bottle when you don't know what is leaking is a very expensive way to find the leak.

[plyonsMC9]

Thanks for all the replies!!  Are these last posts talking about the REAR beams or front beams? 

My mechanic says if only the rear beams, it isn't a problem.  However, I can also see that one of the problems of plating looks like they will also eventually rust, and the fix is not truly permanent.

Thanks again!

Phil

[JackConrad]

My reply was the rear air bags.  I still have the air beams in use on the front axle.  Jack

[plyonsMC9]

10-4.  Thanks Jack. 

Best Regards, Phil