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tenfive0

Air Dryer or Not?

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Posted (edited)

I have a retired 1972 CF-600 that does not and never has had an air dryer. Contemplating if i really need one? The truck doesn't get used much and if I keep aware of the issue of condensation in the tanks and drain them regularly do I really need a dryer. 

Edited by tenfive0

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Nope.  Monitor/drain your tanks and you will be fine.

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I bought the truck last August with 37,000 plus miles on the odometer. I've only put about 700 miles on it since I've owner it. Today was the the first time I drained the tanks and I got around a cup of water. I have no idea when or how often the tanks were drained before I bought it. The wet tank and primary tank 1/4 turn drains are in an awkward position. I might put pull drains on the wet and primary tanks so I won't have to crawl around in the dirt to drain the tanks regularly.

 

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Posted (edited)

In freezing weather you do well to have an air dryer protected system. The other thing you need to consider is low pressure freezing. In other words compressed air moving from high pressure to low pressure creates ice. An example is the ice which forms on a carb Venturi on a hot engine. Just because you are in a warm climate doesn’t mean you can’t have ice form spontaneously in your brake system and cause trouble temporarily till it thaws. Rapid brake pumping could bring on a freeze inside an R valve plunger. The drier the air the better.

On one hand you can argue it never had one. On the other hand they made a policy for installing them for good reason. 

Edited by Mack Technician
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Prior to air dryers they used alcohol. Just drain tanks then suck some air system alcohol through the compressor intake before winter time.

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Still do use alcohol. It keeps things from freezing in the winter but the tanks still corrode from the moisture laden air. The air dryer helps with both freeze ups and moisture content reduction. If maintained very little oil gets past the media that causes sludge downstream too. 

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I just put new drain valves on the little Midliner box truck I've got. It has a three-tank system with no air dryer as well, though it did have some goofy Haldex automatic purge valve on the wet tank, which had failed. The pull-type valves are significantly more convenient and if you stick with no air dryer they will probably get you to blow down the tanks more often. I bought Tramec-Sloan 1/4" NPT valves and just drilled out and tapped the old plugs that held the old drain valves. Two of them were metric (a Midliner is really a French-built Renault) and the other was the goofy integrated Haldex thing. Now I also don't have to worry about finding an oddball part if one should happen to break on the road.

I plan on replacing the air system at some point and when I do I will put an air dryer on, for all the reasons stated above. I figure that, until I actually replace everything, there's no point in using an air dryer on the current system.

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9 hours ago, tenfive0 said:

I have a retired 1972 CF-600 that does not and never has had an air dryer. Contemplating if i really need one? The truck doesn't get used much and if I keep aware of the issue of condensation in the tanks and drain them regularly do I really need a dryer. 

An air dryer is a wise investment. And, the price of the units with the spin-on desiccant cartridge has become so inexpensive that it's a no-brainer to add one.

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I have a couple AD-4, and AD-9 series in the shop for project trucks. Couple of mine still have AD-2 series dryers and they all work well. I pick the service kits up during sales so they're ready to go.

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I have a couple AD-4, and AD-9 series in the shop for project trucks. Couple of mine still have AD-2 series dryers and they all work well. I pick the service kits up during sales so they're ready to go.


What is the difference between the AD-4 and AD-9?

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The AD-9 series is newer than the AD-4. There is less hardware and disassembly with the element being less expensive than the AD-4 series also. IIRC the AD-9 has a better heater or thermostat along with bottom purge plate incorporated but I've not had problems with either myself. I tend to change elements every two years in the pre winter service timeframe using only genuine Bendix or Haldex reman filter cartridges.

The newer styles with the spin on cartridges are even easier yet but they are a bit expensive to acquire. I've also replaced two myself that were leaking; one cracked housing and the other from the purge valve not sealing and not serviceable. Simpler is not always better.

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I was leaning towards eventually investing in a Bendix AD-9 air dryer. But for now don't fix what isn't broken if I can squeak by with the way it is for now. It's works or has worked the way it is for the pass 47 years and 38,000 miles. There are other pressing (time and money) issues with the truck I need to invest in before an air dryer. In the meantime I'll keep on a look out for a reasonable priced dryer because it is something that needs attention. 

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Is there an easy way to differentiate between the AD-4 and AD-9?

It looks like on the AD-9 the control port is located just above and to the left of the supply port.

It looks like on the AD-4 the control port is several inches to the left of the supply port like this photo

b59a365da45826f14182ada626f88540.jpg

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On 6/24/2019 at 9:20 PM, Quickfarms said:

Is there an easy way to differentiate between the AD-4 and AD-9?

It looks like on the AD-9 the control port is located just above and to the left of the supply port.

It looks like on the AD-4 the control port is several inches to the left of the supply port like this photo

b59a365da45826f14182ada626f88540.jpg

Attached pictures of a Bendix AD-9 I just picked up for my truck. I'm new to the air dryer thing. I don't know the difference between an AD-4 or an AD-9 but I thought a few pictures might help for a comparison.

Mack 633.jpg

Mack 634.jpg

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