I am trying to sell my 81 MCI MC-9 and last month it aired up fine. There was a little spittle from the tank but stopped. Today, after it was cold the past few days, I cannot get the bus to air up at all.
I turned the front wheels and can here where the air is spitting from and have taken a picture of it.
We're are the drain valves on this bus (with pictures)? And what/why am I hearing the air spit out of the bottom of this tank?
What is the fix?
I can't get under the bus...
Use a long stick and reach in there and try taping the bottom of the middle to try to close the purge valve on it. That is your Air dryer. on the wall behind it if you look the other way you have to tanks that hang down and should be a drain on each but that is coming from the bottom of your airdryer. It opened and cant shut because it is stuck open or has something keeping it from closing and building up air like rust if you have never drained the tanks. HTH
Only other way is to jack her up and support it with heavy duty jack stands or wood blocks and take off the bottom of it (AD2 its called) go to a Napa store and get a purge valve rebuild kit and new Desiccant filter cartridge.
Whether whacking it works, it will fail again shortly.
It needs the replacement of the purge valve, and be sure to get the model with the 24 volt heater in it, and get the wire properly attached and powered.
It freezes stuck in the cold otherwise...
Where are you? Another busnut may be nearby?
Happy coaching!
Buswarrior
You can buy the Purge valve ( it just unscrews from the bottom plate)with out the bottom plate, just check the heater wires to make sure you have 24VDC on the wire when key and or heater is on in the coach then let it run and see if it is hot on the box with the wire attached. That was just to see if it works and you can air it up and if so Like BW said get the rebuild kit because it will do it and soon again but if the heater works you don't need to put out the money for a whole bottom plate.
The air drier heater is powered via the coach heat switch.
There is often an inline glass fuse holder stuffed into the outside driver's electric box that is involved too. 3 amp IIrC?
Coach is for sale? Minimum effort and expence is going to be expended here...
Happy coaching!
Buswarrior
Isn't the air dryer heater on a thermostat? Like it only stays on when it's cold out?
Rebuilding the whole dryer is cheap and easy. Desiccant cartridge and purge valve are less than $100 at the heavy trucks parts stores. It is preventive maintenance that is necessary to insure trouble free travel in the winter.
JC
Quote from: lostagain on November 18, 2018, 07:24:26 AM
Isn't the air dryer heater on a thermostat? Like it only stays on when it's cold out?
Rebuilding the whole dryer is cheap and easy. Desiccant cartridge and purge valve are less than $100 at the heavy trucks parts stores. It is preventive maintenance that is necessary to insure trouble free travel in the winter.
JC
Yes the thermostat is set to come on around 40F lol when they work
Thermostat is built in.
The way MCI wired it, thru the coach body heat switch, means it only sees power if the coach interior needs heat.
Busnuts often screw this up during tear out, remove their coach heat, never turn the switch on, and freeze the purge valve.
Yes, a full service of this drier is obviously overdue... not likely going to happen if a low post count busnut is trying to sell the coach...
Happy coaching!
Buswarrior
Quote from: buswarrior on November 18, 2018, 07:40:10 AM
Thermostat is built in.
... not likely going to happen if a low post count busnut is trying to sell the coach...
Happy coaching!
Buswarrior
That's brutal... ??? FWIW-thermostat is supposed to kick in at 38° F-don't ask me how I know.
Thanks everyone, have had this coach for about 12 years and never got to use it after finishing in. Too many kids came (4) to go out in it.
I'm super cautious about getting under the buss... how do you drain the tanks without getting under the bus? If they are supposed to be drained daily certainly doesn't make much sense to have to get under the buss to do it....
One of those things I wish were posted everywhere like "diesel fuel only) 🤦🏼♂️
Put auto drain on each tank, pretty expensive or like I did get the cable pull 1/4" drains to replace the manual drain-cock valves. You can get them on line but you will have to get under there to install them but will anyway to fic or rebuild your air-dryer. :)
https://www.amazon.com/Midwest-Control-DP25-Degree-Temperature/dp/B01KO7CNW6
The only two tanks that are hard to get to are the parking brake tank (passenger side front wheel well) and the wet tank (driver's side). When I started I used what I later found was a fifth wheel pull stick to reach under and pull on the loops on the drain valves. Later I installed new cable pull drain valves and routed the cables to inside the fuel fill hatch. The tank that really needs daily draining when operating daily is the wet tank.
IMO Auto drains are....stupid.
They fail.
With cable pull drains, it takes no time at all to know they have been drained, and you get to walk around your bus, something you're supposed to do.
Who doesn't do walk arounds...
People with out cable pull drains.
Ditto.
A busnut needs to watch what comes out, looking for "regular"
Auto drains leaves the busnut blind as to developing problems.
And, they stop working. How will the busnut know that?
A busnut is owner, financier, mechanic as well as driver.
Ignore what your rig is trying to tell you, at your peril?
Happy coaching!
Buswarrior
Thats why I said "I put cable pulls on mine" :)
purge valve rebuild kit
Does anyone have a part number handy? I've searched everywhere and seems MCI made has used several dryer models. I went to the NAPA site but nothing came up with just text searching. MCI website doesn't help because I can't access anything... There used to be some sites for model specific busses but those seem to of disappeared or the host of those sites no longer maintaining them.
Thanks for all the help. Want to get the part ordered so next time I'm in Huntsville I can repair it.
MC9 probably has a AD9 dryer. To be sure, take the purge valve assembly off and go to a truck parts store. They will have it on the shelf. Very common part.
JC
In the pic at thread beginning, the air drier is tall.
AD2 air drier would be my bet.
MCI just kept using them, and using them, and using them...
Stolaas, you really need to pull off the existing part and take it to the local truck parts place so you only take one trip.
Call ahead/around to be sure they have one in stock to compare to. The mechanical sizing is the same for 12 and 24 volt models. You may have to wait for a 24 volt to be ordered in, unless there is a pocket of obscure demand in your area and they have them in stock.
happy coaching!
buswarrior
I happen to have a Bendix AD-2 purge valve kit in my hand, awaiting warmer weather for an install. Bendix part number 287053N. Does NOT include anything related to the heater except for a new rubber boot to cover the wire connection, contains only the instruction sheet, various seals, springs, silicone grease and O-rings. It was ordered from Bendix by my local truck parts place in Truro, Nova Scotia, no problems, in stock at the warehouse. Cheap.
Edit; if you download the AD-1 and AD-2 manual sheet PDF from Bendix (google it) the last page has all the rebuild kit numbers, including the thermostat kit, and several others. And instructions.
http://www.bendix.com/en/servicessupport/documentlibrary/doclib_1.jsp
Enter "dryer" in the search box
Page 4
TCH-008-000 AD-2 AIR DRYER SERVICING
Select download
Wanted to show a picture of the Purge valve in case anyone in the future would like to know what it looks like. Really easy to get off and got the rebuild kit online. Had to dig a trench from the front of the bus to get to the location directly behind the front axel.
Works great now. Only problem is now there is some kind of loud purge at the rear keeping the bus from building to 120 psi to allow the front purge to operate. I took a video of the sound from the engine compartment. Was happening just like a purge every minute or so, even when I killed the engine it still continued every minute for about four or more cycles till the rear end was deflated. Front bags still had air...
Video of the rear Purge? I can't tell wear it is coming from or where the rear tank might be if it is coming from there. The bus is drivable now at least, got it moved out of the yard. FYI it is for sale with Offer :)
https://www.dropbox.com/s/hwjcrl8nrkmf49j/IMG_1850.MOV?dl=0 (https://www.dropbox.com/s/hwjcrl8nrkmf49j/IMG_1850.MOV?dl=0)
I figure there is much dirty water to be drained in my immediate future...