Using the bus as an air compressor.

[plyonsMC9]

Well I thought I had a great idea - to use the bus air valve on my MC9 for occaisional air uses if necessary.   Maybe even in an emergency situation as well.  I knew a guy with a Barth (kind of a bus?) that did that years ago. So I thought it would be great.   I tested it at home, and it worked great. 

We were out with some friends and I thought I'd show off how cool this was.  Well, I plugged in my hose to the fitting, told my friend "watch this", then I turned the valve.  Exactly NOTHING happened.      I took all hoses off the valve.  Said "watch this" again.  Ahem, still nothing... 

The bus was at about 90 LBS.  pressure.  What gives?  The only difference I can think of is that when I tested this at home, I had aired up the bus from an external air compressor.  Whilst at the campground, the bus still had plenty of air in it from the engine running earlier. 

Any thoughts?  Should this work? 

[Hartley]

Directional valve on air tanks. Accessory air for the Tag axles on MC9's comes from the aux tank I think.

Although I thought mine has the tap for that outlet in the first oil-drain filter after the
compressor. That's why there's a drain valve there to let you drain the oil out of the line
trap.

Without the engine running and system pumped up, very little air will be available at the
drain valve next to the tag regulators.

There is a directional valve located after the main air feed line and the tank pressure feed valves
prevent backflow from the tanks back into the compressor line.

With the engine running you can have up to around 15 cu.ft per minute air directly from the compressor
at about 1,200 rpm. at that tap.

[Dallas]

Phil,
You are probably not taking air off the live line, but after it leaves the leveling valve.
Try hooking up to the wet tank live air
that way you'll have air no matter what, as long as there is air in the tank.

IHTH

Dallas

[NewbeeMC9]

That line comes off the bottom of a filter.  Not much air there except when the bus is running and the governer is cycling.  Do drain it every know and then when it is running.   i try to do it and the tanks right before I shut it down if feasible.

[gumpy]

Phil,

Hook your air fitting up to the aux tank under the driver. You'll get a better reaction from your friend.

craig

[plyonsMC9]

Well put Craig - "better reaction from my friend" -          LOL - Way too many times I say " now watch this.... "  and then I get the unexpected results.   Kind of like Bullwinkle, forever saying "watch me pull a rabbit outta my hat".    OK, I'll try from under the driver today.  Thanks -

NewbeeMC9, I'll try to post that pic today as well of the valve area.

Kind Regards to all - Phil

[JackConrad]

Way too many times I say " now watch this.... "
Phil you want to be careful saying this.   Remember that a renecks last words are usually:
"Hey Ya'll, Hold my beer and watch this!"

[plyonsMC9]

aaaaaack !!!   Too FUNNY! !!       But wait, maybe I better Stop saying that.. ..     At least nothing has exploded after I said that...   

Recently...   

Best Regards, Phil

[plyonsMC9]

Phil,

Hook your air fitting up to the aux tank under the driver. You'll get a better reaction from your friend.

craig

My air tank under the driver doesn't have an air fitting that I can see.  Just a copper (i think) tube going off of it towards the center of the bus.  Do I need to add a fitting to the tank?  I do see some kind of pull ring at the bottom of the tank - but I don't know what to do with that.  I'm a little hesitant to pull on things w/o knowning what will happen to me.      

Thanks again - Phil

[plyonsMC9]

Phil,
You are probably not taking air off the live line, but after it leaves the leveling valve.
Try hooking up to the wet tank live air
that way you'll have air no matter what, as long as there is air in the tank.

IHTH

Dallas

Thanks Dallas, can you point me to the general area of the wet tank?  I have an '83 MC9. 

Would I need to add a fitting for my air hose?

Kind Regards, Phil

[Dallas]

Phil,
You are probably not taking air off the live line, but after it leaves the leveling valve.
Try hooking up to the wet tank live air
that way you'll have air no matter what, as long as there is air in the tank.

IHTH

Dallas

Thanks Dallas, can you point me to the general area of the wet tank?  I have an '83 MC9. 



Would I need to add a fitting for my air hose?

Kind Regards, Phil

Phil,
I'm not sure about the MC9 for the wet tank physical location, but it will be the first tank after the compressor, and yes, you will have to add a quick connect fitting to it to hook your air hose up to.

While your at the plumbing of this line, you may want to add a ball valve and a tee to put a male quick connect onto. This way you could air the entire bus up with an electric compressor in an emergency or for diagnostic purposes.

A little advice here, it might be a good idea to install an air filter to keep the air coming out a little cleaner and an air regulator with guage to limit the amount of air going to your air operated tools. Many of them aren't designed to operate on more tha 95 lbs. of air pressure, while the compressor will pump up to about 120.

Most likely, the pull ring on the tank under the drivers seat is either a drain valve and should have a cable to it for easy access or it is the over pressure pop off valve.
To use any of your tanks you'll have to install fittings to hook up an air hose.

I always buy Campbell-Hausfield fittings even though they aren't as good as other brands, because they are available everywhere and are a standard size. There are lots of different sizes of quick connects and many of them don't interchange. If you use the C-H brand, most of the time you won't have a problem connecting to other hoses.

If I can be of any more help, just holler!

Dallas

[JackConrad]

Phil,
   I think your wet tank is in front of the drive axle attached to the backside of the bulkhead that forms the rear wall of the rear baggage compartment. You will have to run a line to a more accessible location. The easiiest way is to use a length of 3/8" DOT approved plastic/nylon brake line. I would run this to the area just inside the passenger side engine comparment door where the tag axle switches are located. Then plumb as Dallas recommended.  Hope this helps, Jack

[gumpy]

  I do see some kind of pull ring at the bottom of the tank - but I don't know what to do with that.  I'm a little hesitant to pull on things w/o knowning what will happen to me.      

The ring pull is the drain valve. You should know where these are so you can use them periodically to drain any moisture from the tanks. All the tanks have one.

I pulled the drain valve on the aux tank and installed a T fitting with the drain valve on the bottom and the air coupling to the side.

[gumpy]

Phil,
   I think your wet tank is in front of the drive axle attached to the backside of the bulkhead that forms the rear wall of the rear baggage compartment. You will have to run a line to a more accessible location. The easiiest way is to use a length of 3/8" DOT approved plastic/nylon brake line. I would run this to the area just inside the passenger side engine comparment door where the tag axle switches are located. Then plumb as Dallas recommended.  Hope this helps, Jack

Jack,

I was thinking the wet tank is one of the front tanks and the rear tank is the brake tank. I'm pretty sure the rear brake hoses are connected to
the rear tank.

I may be wrong, though, so if someone knows for sure, please correct me. The air system is one area I have not fully deciphered yet, as my schematic is not very clear. I did finally get a non-reprint manual with clear schematics, so maybe if I remember, I can look at it tonight.

craig

[JackConrad]

Craig,
   You may be correct.  My MC-8 is an early one ('73) and I know MCI made some changes in tank locations. Is your air dryer in the front or rear of your bus? I think it is usually close to the wet tank. My dryer is in the rear along side 2 air tanks.  Jack