Geoff Weeks

Just a warning, mine went from just a little problem to not being able to pull a load in less than a day. One of the 2 times in my whole time owning trucks, that mine was on "the hook". The other was when the fuel pump "self destructed" Running just fine one moment, and dead the next. Got to go, can mean not making it plus a tow bill. Better to delay a partial day to address the problem, then loose 2 days when it shuts down and has to be towed in. Just a little hard won experience. Not only do you have the repair bill but you have the tow bill as well.

I had my truck have somewhat similar problem. It was the suction line from the tank to the pump. On hard pull it would draw in enough air to cause a problem, lighter work, it would tolerate the little air just fine. A new hose and the problem was fixed. Just something that is easy enough to try, and given the state of the other hoses on the truck, I would say is a good bet. Stratoflex etc hoses don't last forever.

TBH, I would not be concerned about the engine, They should be able to handle full load continuously. As long as radiator and charge cooling is in good shape, that isn't the weak point. 350hp with 120k is doable but slow. It is the frame and rest of the driveline that concerns me.

Although I unloaded at -30F in Montana, the coldest I have worked was on US Steel coke battery in Gary, In. It was -20 or so, and the burning coal (coke) gets pushed in rail cars then quenched with water. One sec blasted with heat, the next steam turning to frost. The wind blows right off the lake. Set down a tool and it freezes to whatever you set it on. I made the repair and got out of there ASAP. Cloths got frozen,hard to move. The heat never lingered long enough to help, and the cold stuck around.

Because, they know we just gave away any moral high ground, we didn't loose it, we gave it away. They are thrilled.

Ah grasshopper, special air drier made for Mack mechanic, not for IHC man!😄

Turns out desiccant for the AD-2 is available: AD-2 desiccant

Never heard of one, and the internet doesn't return any hits. is a AD-IS? that take a spin-on cartridge. there is AD-SP which is Bendix version of the Meritor spin-on and requires purge air from the secondary air tank. The early air driers have internal purge volume, so don't need extra tanks or a SC-PR valve (a check valve that allow a set amount of air back to purge the drier. With air start trucks, I wanted to make sure my air was dry. The AD-4 did that for me and didn't need a lot of baby sitting. I had 2 AD-9's fail, and I swore I wouldn't have another. One the threads in the base failed, the other the outlet check failed.

I doubt the AD-2 is the problem. I have one that is still going fine. I'd put my money into replacing hoses before I touched the air drier. When I scrap the Fleetstar with the AD-2, it is going on my K-7, only drier that will fit behind the cab under the body. I took off all newer driers (AD-9 and Rockwell/Meritor) and installed AD-4's. Even converted some AD-9's into AD-4's with the addition of a plate and base. The older driers are a pain to service compared to a "spin on" or single bolt (AD-9) but will out last them hands down. If you take care of the air system, so it is not popping off all the time, an air drier will go years perhaps decades without being serviced (yes, I know decades is not recommended). When you start to see moisture out of the wet tank, then look at the air drier, if the rest of the system is up to snuff.

The vast majority of the time when a vehicle has trouble "building" air, the problem is it is having trouble holding on to the air that has been compressed into the system. A system that has a true "building air" problem, will hold the air just fine after the cut-out pressure is reached, it will hold at 120 psi with the compressor unloaded for a long time. Much more common is for the system to rapidly loose pressure, start compressing again, then loose it once the compressor unloads. Check for air leaking out of the purge valve on the bottom of the drier when the compressor is active. You should get a burst of air followed by a slow release of air out the purge valve when the compressor unloads. A leaky air line between compressor and drier will act the same. A leak after the drier will cause rapid cycling of the compressor.

What problems are you noticing? My guess it you're hearing it pop-off frequently? That is not the drier but the air system. Replace the hoses going to the drier and see if that doesn't cure most of what you are hearing.

The hose from the compressor (in to the bottom of the drier) looks like it is well past its "use by" date! I'd be replacing that before I did anything else. That looks like it is about to pop and likely is already leaking badly. Yes, the AD-2 is much taller and skinny when compared to new ones. I'd fix what you have, the AD-2 and AD-4 work well but are less "user friendly" when it comes to service, never the less, will outlast just about all the newer ones. really all the hoses connected to the drier look bad.

AD-2's are still around because they fit where many other style will not. Tall and skinny. Parts and rebuilt end covers are still available. Be advised, the end covers are made in both 12 volt and 24 volt models. The voltage is for the internal heater that keeps the valves from freezing up in cold weather. Replacement desiccant cartridges are also available. I would not disassemble the cartridge as I doubt you can get replacement beads. You just buy a whole rebuilt cartridge.

Here is Lit on it. Bendix AD-2.pdf

AD-2 extended purge from the look of how tall it is, unless that it just a trick of the picture. Anyway you cut it, it is an AD-2. Edit: Looking more closely, I think it is a regular AD-2 just the angle of the shot made it look taller.