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Author Topic: Air Bag Installation in MC-8  (Read 1154 times)
DavidInWilmNC
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1978 MC-8 as I bought it May 2005




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« on: July 15, 2006, 10:15:06 AM »

Hey guys,

I replaced the left side drive axle leveling valve last week.  This cured the lean on that side of the bus.  I found that the air bag was leaking where it meets the top plate/mount attached to the air beam.  It seems that when it was installed, the nuts weren't tightened -- they were about 1/8" from contacting the plate and rusted in that position.  Anyway, I ordered a new bag and hardware (bolts, nuts, and washers).  I've cleaned up the mounting plates and am getting ready to paint them.  There is some pitting where the rust was on the surface where the bag will seal against the plate.  How crucial is it that this area be completely smooth?  I'm not sure that I can get it any smoother than it already is.  Will the bag conform to the area in question and seal or should I use some sort of sealer on it?  Other than the fact that it took me FOREVER to get the nuts removed / broken off the bolts, it seems fairly straight forward.  I also bought new rubber bumpers that keep the suspension from banging if it bottoms out.  Does anybody have a suggestion for removing the old ones?  All I have left is a round metal plate with a bolt rusted in it.  Thanks for any input!

David
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DavidInWilmNC
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« Reply #1 on: July 15, 2006, 06:00:43 PM »

Come on guys... any input before I try to install the air bag tomorrow?   Thanks!

David
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Happycampersrus
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« Reply #2 on: July 15, 2006, 06:45:32 PM »

David,

If the pitting is severe, sand the plate down smooth as you can and mix up a batch of automotive bondo. Skim a coat on it, let cure, then sand smooth. primer & paint.

Light pitting won't hurt the seal. The top of the airbag will seal small pits. I hope this helps.

Dale
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pvcces
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« Reply #3 on: July 15, 2006, 10:20:01 PM »

Is it practical to add another plate to the existing plate before installing the bag? I know that rust will leak air, so you will want to get rid of the rust in the seal area.

For what it's worth.

Tom Caffrey
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Ketchikan, Alaska
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Tom Caffrey PD4106-2576
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JackConrad
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« Reply #4 on: July 16, 2006, 05:15:15 AM »

David,
     Here is how I replaced the bumpers on our MC-8. As with yours, the bolts had rusted off and were flush with the top of the place the new bumper sits. Because there was not enough room to get a drill in there to drill out the old bolt, I took my torch and cut out the old bolt making sure not to enlarge the hole. I then cut a "window" in the side of the piece the bumper attaches to. Set the bumper in place, drop a bolt down through the hole and install a flat washer, lock washed and nut. After tightening the nut, the "window" was sealed with a piece of HVAC aluminum tape. 5 years later the tape is still in place. I used the yellow poly-urethane bumpers from International Bus & Parts.
    As far as the rusting and pitting, it depends on how bad it is, difficult to say without seeing it.  Whenwe replaced our airbags, we went to rolling lobe so the pitting was not an issue.  YMMV Hope this helps, Jack 
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DavidInWilmNC
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« Reply #5 on: July 18, 2006, 06:17:05 AM »

Ok, I got the bag replaced... what a job!  I'm sure the next one will be a LOT easier and quicker.  I cleaned and painted the plates with something similar to POR-15.  This is a plastic-like paint that should seal the metal and prevent future rust.  I decided that the plates weren't in all that bad a shape and to try the bags without smoothing them down any.  The rust-preventing paint is fairly thick and I think that helped some.  The bags themselves weren't so difficult to install.  Getting all those bolts through the plates and lined up sure was a pain!  After about an hour and a half, I had the bags installed, all the bolts lined up and tightened, and the bus aired back up.  I set the ride height at 5 1/8" (per the manual).  This was last night; this morning, the height had dropped less than 1/8", which I don't consider to be all that bad.  Of course, I'd like it to stay up indefinitely like the other side does.  I'll check again this evening after work and spray some more soapy water on everything and check for leaks.  So, after replacing a sticking leveling valve and a leaky air bag, my bus finally sits level!  It's been leaning towards the left about 4" since I've had it.  Thanks for the input regarding my questions about the plates.

David
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