Bus won't air up

[PP]

I'm trying to get off this mountain and the weather is holding but the bus won't air up. I found the leak, but I'm not sure what to do about it without knowing more first. Air is coming out of the bottom of a large vertical cylinder mounted between the tag axle and the drive axle just a little off center more to the passengers side. It has an airline going into the side about halfway up and another near the bottom with an electrical connection also at the bottom. There is a small screw holding a soft rubber washer which I believe is just to keep dirt out and what looks like a 2+ inch nut on the bottom. I can grab a pic if that helps. I've tapped it which only increases the air or slightly decreases the air coming out depending on which side of the big nut I tap.
Wife is now threatening to sell bus if I can't get this solved quickly. Please help. Thanks in advance, Will

[niles500]

Believe you are describing your air dryer, is it frozen open? What is the ambient temp? Could also be the air governor, that's what controls it

[Dave5Cs]

Will sound like your air dyer. The valve that is letting out the air on the bottom is the Purge valve and is probably stuck open and letting all the air out instead of building up. The electric thingy is the heater for it so it does not ice up and not let air through to the rest of the system. Take a broom handle and tape the bottom of the rubber thing a few time and see if it will close. If not you may have to block it up ( the Bus) and get under there and replace the purge valve. It unscrews and new one from NAPA will screw back in with new o ring. Might need to get a full rebuild kit for the air dryer to include that valve 2 check valves and a desiccant cartridge.HTH
Dave

[Fred Mc]

I had the same problem a month or so ago, except it was the govenor. The bus wouldn't air up and we had to vacate the campsite. The onyl difference is that it was me who thought about selling the bus.Wife looked at it as and "adventure".LOL

[PP]

Thanks guys. I found Fred's post from a couple weeks ago and it is the purge valve that is stuck open. I used my 120V compressor to air up the suspension and then put a couple of blocks under it to keep it up in case I did something stupid and then got a wrench and tapped on the valve. It instantly started shooting out more air, so I tapped on the other side of it and it made a pfft noise and started working. It's working fine now and I'm holding a solid 120PSI at low idle. A new purge valve is definitely in the near future just as soon as we hit the coast. This set us back a day, but weather in the pass is supposed to be in the 60's tomorrow so all is good. Even the wife is back to normal and agreeing that we need to replace the valve ASAP.
Again, thanks for the quick responses,
Will and Wife

[luvrbus]

LOL if Will didn't know what that was, I say that dryer has been overlooked for years on the service end,now is the time to change to a AD-9 parts are getting expensive and hard to find for the AD-2 or AD-4   

[PP]

LOL if Will didn't know what that was, I say that dryer has been overlooked for years on the service end,now is the time to change to a AD-9 parts are getting expensive and hard to find for the AD-2 or AD-4   

Sadly Cliff that is too true. I change oil, filters, and lube it regularly as well as checking brakes and replacing tires. But I do find myself hoping for the best on everything else. I have looked into the AD-9 dryers on Ebay a while back when someone brought the subject up here so maybe that isn't too far into the future. 
Will

[luvrbus]

Don't we all Will watch those on Ebay some say AD-9 style or replacement nothing on 1 is Bendix, they are just Chinese made knockoffs 

[TomC]

Rather than trying to rebuild my AD-9, I just got a rebuilt with warranty (about $150). Was MUCH easier than trying to rebuild the old one-which ironically is obsolete now-just enough different than the new ones. Good Luck, TomC

[Oonrahnjay]

Rather than trying to rebuild my AD-9, I just got a rebuilt with warranty (about $150). Was MUCH easier than trying to rebuild the old one-which ironically is obsolete now-just enough different than the new ones. Good Luck, TomC 

      And probably not a lot more expensive than buying the parts (not to mention your time and effort).   Good tip, Tom.

[bevans6]

I just ordered a purge valve kit for my air dryer, AD-2, for $25 direct from Bendix, so it's possible.  On my bus the purge valve heater is controlled by the passenger heater - if the passenger heat fan is on, the air dryer purge valve heater (thermostatically controlled) gets power.  If you don't use bus heat, maybe your heater never comes on.  When it's cold out overnight, a real good tip is to fan your brakes just before you shut down to below the governor cut-in air pressure (usually 90 - 100 psi) and get the purge valve closed with the governor/air compressor delivering air.  That way the purge valve freezes closed instead of open, and the warm air from the compressor thaws it.  If you don't have the right sized thin-wall socket to remove that large 2" or so nut, you can do it with a carefully applied pipe wrench around 12" long.  I did it two weeks ago to get my leaking purge valve to stop leaking.

[PP]

Temp was around 20° F this morning. I plugged the block heater in and set a small cube heater next to the turbo. She fired up like a champ and aired right up. It was only a 4 hour trip to this park, but she never missed a beat. Even on a 7 mile grade of 6% she never rose above 185 temp and pulled at 50 MPH without having to put my foot in it. I am covered in some kind of chemical deicer and the toad is now a charcoal black, but it was a great trip. Love this bus! Wife even helped me clean some of the crud off the stainless and I didn't have to bribe her with a seafood dinner. When I shut it down this time, I followed Brian's advice about fanning the brake pedal and dropping the PSI down to around 90 before I shut it off. Maybe I can buy me a little time because I know I can't work on it here.
Thanks again for all the advice and comments (Cliff  ) hehe
Will and Wife

[windtrader]

@PP

Temp was around 20° F this morning

Just curious where in the hell is it 20 degrees now? So sheltered here in Calif but do need to figure out how the Wabsto work before it does get cold (i.e. 40 ish) lol

[belfert]

One thing to check is if your purge valve is 12 volt or 24 volt if it is heated.  I assumed my purge valve was 24 volt so I put in a 24 volt replacement.  I had problems with the air system freezing up when cold.  It turns out the purge valve was supposed to be 12 volt.  I replace the purge valve and the cartridge and no more issues.

[brmax]

I say replace with a rebuilt, as Tom mentioned especially being this long.
Driving it up on some ramps and chalking the wheels is a good priority. As all the air will need to be dumped to replace the unit. Also the good tip to check for the amount of voltage supplied on that wire is critical for purchasing replacement.

Good day
Floyd