Air Tank Drain

[AJ]

On a MC8, where are the air tank drain cocks and how often (miles or month) do you drain them?

AJ

[Ed Hackenbruch]

They are on the tanks themselves, best to just go ahead and drain them every time you run the engine.

[busshawg]

I second that advice ED. everytime will save lots of frustration down the road

[Ed Hackenbruch]

AJ,  napa has air tank drain lanyards for about $15 each that make it a lot easier to drain your tanks once you install them.

[gus]

I drain mine every morning if the temp is above freezing and at night right after shutting down.

Trying to drain during freezing temps is asking for a broken drain valve.

[Chopper Scott]

Actually draining them in the summer (higher humidity levels) is more important than during the winter when the air is dryer. Hard to believe draining the tanks over the 4th of July is more important than on Christmas to keep from freezing up the system but it's so. Not to change the subject but I have the alcohol evaporater system on my bus. The airlines going to it were bad and I had to redo them or eliminate them. Hopefully it's working as I haven't ran it enough to tell yet.

[bevans6]

A large part  of the reason for regular draining is to check on the health of the air compressor and the air dryer as much as to actually remove any fluid.  If those two beasts are in good working order, then you'll get next to no fluid out of the wet tank, and none at all out of the other tanks.  But if your compressor starts throwing oil, you'll notice it by observing what comes out of the wet tank, and by watching the air dryer during a purge.  So along with simply draining the tanks is a good maintenance check just by having a gander at what comes out.  Also - there are various pressure protection valves and check valves in there.  By draining the tanks fully in a particular order, and looking at the pressure gauge on the dash from time to time you can verify the operation of these valves - again good preventative maintenance.

BW once had a really good tip that I took to heart - if you are in freezing temps always fan the brakes and make sure the air compressor is on a fill cycle before turning the bus off for the night.  That puts the purge valve in the air dryer in the closed position, and makes sure it doesn't freeze open over night.

Brian

[desi arnaz]

where are the tank drains on a 4106  and how do i get to them?

[johns4104s]

I drained my MCI 9 today, Pulled the lanyards before I started the engine, Nothing. I felt great. Then after I started the engine I went underneath and pulled them again, WOW , water poured out of the front wet tank, I say poured, about a large cup full. So what it proved to me was its no good to pull them without the engine running.

John

[bevans6]

If your tank on the MC9 is similar to the one on my MC5, the drain outlet is about 2" higher than the floor of the tanks (except for the accessory tank, where the drain is on the bottom).  I suspect there is an internal tube to get down to the floor, but I don't know for sure.  But yes indeed, you must drain the tank when it has air pressure to blow out the fluid!  The engine doesn't have to actually be running, just air pressure.

Brian

[buswarrior]

Hello AJ.

There are 4 tanks on your MC8.

One in the compartment outside, under the driver's seat, mounted against the ceiling.

Two mounted on the bulkhead in the cavity where the front axle is.

One mounted in the drive axle cavity, on the other side of the last baggage bay bulkhead, it nestles in that bump into the baggage bay.

As well, there is a discharge muffler drain in the curb side engine access, usually mounted to the back of the tag axle wheel well.

As noted, draining the air system is a frequent and all year long preventive maintenance practice.

You will note on both boards, many busnuts who were caught with their pants down on this topic, with the unexpected deep freeze finding its way much further south than they would like!

Freezing temperature functionality is easy, if you take the time.

happy coaching!
buswarrior

[Gary LaBombard]

This is a stupid, stupid question I am sure I will be told but what happens to your air bags when you drain your air tanks??  Does this have any effect on the air bags doing their job holding up the bus when parked?  I have no idea how the MCI's or any bus with air bags work so I am just curious.  My plan for my Eagle, if ever roadworthy is to follow the above advise and drain them daily as well like I do my shop compressor that is in a insulated shed but sure builds up with water inside very easily especially in humid days.

Don't laugh at my ignorance on this question, as I do know the air must have to leave a tank to fill up the air bags, is there a one way valve that holds the air in each bag to prevent the bus from being lowered down when the tanks are emptied?

Well here come the flak!!

Gary

[JackConrad]

Gary,
  On the buses that use air bags for suspension, the air bags are controlled by leveling valves. These valves only open when the bus is too high or too low. As long as the bus is at normal ride height, the leveling valves are closed and there should be be no air flow out of or into the airbags.
   Now, that is in a perfect world, which this ain't. Leaks in the system, People getting in & out of the bus, wind rocking it, or the leveling valve opening to let more air in, when the air tanks are empty will all result in the coach settling.  Jack

[buswarrior]

And, yes, there are supposed to be check valves in the leveling valve circuit, however, over the years, we have had regular occurrences of busnut buses that after sitting for some time, suddenly deflate because the check valve has been omitted or failed. The leveling valve cracks open, and the air from the bag goes backwards into the empty air tank, which emptied beforehand due to other leaks.

great question!

happy coaching!
buswarrior

[zubzub]

This is a stupid, stupid question I am sure I will be told but what happens to your air bags when you drain your air tanks?? 

Just to clarify, you are draining the moisture out of your air tanks, not all the air.  The moisture condensates and settles to the bottom of the tank, and you open the drain for just long enough to let the water out.  There may be some who leave the drain open till all air escapes but IMHO this should not be neccesary.