Maintenance,Air Dryers/Compressors/Valves

Please don’t be upset with the messenger, but we need to note that winter is officially just weeks away, and the “s” word isn’t far behind, which means cold temperatures are coming across North America. It also means it’s time to be thinking about paying extra attention to your vehicle’s compressed air system.

Dry Matters

Because vehicles are using compressed air for more non-braking functions these days – including automated manual transmissions (AMTs), advanced driver assistance systems (ADAS), other safety systems and emissions controls – keeping the pneumatic system’s air clean and dry has taken on greater importance.

In fact, it’s that “dry” part that becomes even more crucial in lower temperatures: Moisture in the outside air is naturally drawn in when the compressor is charging, and it’s the job of the air dryer to prevent that moisture – and other contaminants – from getting into the system. If the dryer fails to do this, moisture can condense inside the air tanks and find its way even deeper into the system. This presents problems at any temperature, but when it’s cold out, that condensation can freeze, increasing the odds of malfunctions in brakes and valves throughout the vehicle.

Winter factors that can degrade the dryer’s ability to effectively remove moisture from the air include trapped water that freezes and prevents valves from functioning; the additional component strain of freeze-and-thaw cycles; and corrosive road chemicals that can damage a dryer’s purge valve.

What You Can Do

 We’ve written before about the importance of air dryer cartridge selection (and produced a video, too!), so we’ll just do a quick rundown here:

  • Annual air dryer replacement in fall when temps start to drop is good preventive maintenance, especially in cold climates, or on vehicles that consume higher air volumes, like vocational trucks.
  • Bendix recommends OE cartridges: There are a lot of aftermarket products available, and not all are made with the most effective moisture-removing desiccant, and you don’t want to risk compromising the system’s ability to provide adequate winter protection.
  • Bendix also advises the use of oil-coalescing cartridges, since the oil aerosols passed into the system by the compressor can be particularly harmful to air systems, deteriorating seals and contributing to premature damage of other components.

(Full disclosure: We’re particularly proud of the fact that our PuraGuard® oil-coalescing design removes the oil aerosols before they reach the cartridge desiccant, which helps extend the dryer’s capability.) And upgrading is good, too: You may elect to replace a standard cartridge with an oil-coalescing version, but you should always change out oil-coalescing cartridges with like replacements.

Another thing you can do to help keep the air system moisture-free in winter is manually drain the air tanks based on the truck’s air usage. Every three months should suffice for a typical line haul truck, but you may want to consider doing it monthly for vehicles with high air demand.

Finally, we recommend annual air dryer purge valve replacement, especially on vehicles operating in long-term exposure to cold or contaminants like road salts. It’s a bit of quick preventive maintenance that you can schedule along with installing a new dryer cartridge.

Handling Freezes

Traditionally, air system freezes tend to be dealt with in the field by adding alcohol or similar de-icing solutions until the affected area clears. This action is always at the very top of our “do not do” list, because many of the chemicals found in these solutions can corrode the compounds used in brake system seals, or break down valve lubricants, leading to leaks, valve malfunctions, and long-term damage.

That said, Bendix recognizes that some situations may call for the drastic measure of using a brake anti-freeze compound. If you find yourself in this bind, try to determine the precise location of the freeze-up and limit application to that area.

Afterward, when possible, check for leaks around the brake valves if their O-rings were exposed to the anti-freeze chemicals.

Now’s the time to take the precautions to guard against air system freeze. If you’ve got questions, get in touch with the Bendix Tech Team at 1-800-AIR-BRAKE. We’ve also got several Truck Talk with Bendix podcast episodes on air system topics to check out.


Bendix Blog

Technical and industry insight from OUR experts.

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