Tips for Properly Maintaining Air Dryers

Commercial truck air dryer maintenance

In my last post,  Winter’s Coming! Get Prepared With This Inspection List, I mentioned the air dryer as a service item. Let’s take a closer at what air dryers do, what parts are included and how to service them PROPERLY. We’ll be looking at the operation of a Bendix AD-9 Air Dryer.

What they do: Air dryers collect and remove air system contaminants in solid, liquid and vapor forms before they enter the brake system. They are designed to provide clean and dry air to the brake system components to help increase the system’s life as well as reduce maintenance costs and eliminate the need for daily manual draining of the reservoirs.

What parts are included: The air dryer consists of a desiccant cartridge along with an aluminum end cover secured to a cylindrical steel outer shell. This end cover consists of a check valve, safety valve, three threaded air connections and a purge valve housing. The removable purge valve housing uses a purge valve mechanism and turbo charger cut-off feature designed to prevent loss of engine “turbo” boost pressure during a dryer purge cycle. To aid air dryer serviceability, the desiccant cartridge and discharge check valve assembly are screw-in type. The purge valve housing includes the heater and thermostat assembly and a discharge check valve. These two items are serviceable from the air dryer exterior. Servicing the screw-in desiccant cartridge will require that the air dryer be removed from the vehicle.

Proper maintenance: As you can see, the air dryer is made up of many components. Maintenance and maintenance intervals may vary as vehicles operate under different conditions.  The Mitchell 1 TruckSeries truck repair software covers maintenance, service and repairs of these items. Component replacement as well as operation and functional testing procedures are covered.

  1. STEP 1: Examine the dryer and look for a tag indicating the make and model of your air dryer.
  2. STEP 2: Using TruckSeries, navigate to your “Table of Contents,” select “Brakes” and then “Air Dryers.”
  3. STEP 3: The drop-down menu provides a selection of dryers to choose from. Select your model, and you now have access to the information you need for service, maintenance and testing procedures.

Good Luck!


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About the Author

Bruce Cansler

Bruce Cansler started his automotive career in 1973 as a technician for Datsun. He retired from the U.S. Navy as a Seabee Construction Mechanic with 20 active years of service and 10 as a reservist, then spent time working in Ford, Lexus and Caterpillar dealerships. Bruce has obtained ASE certifications in both cars and medium/heavy trucks and has worked with the Commercial Vehicle Group at Mitchell 1 since 2009.