Bendix Air Compressor How to & Troubleshooting Guide
Tips & Tricks

Bendix Air Compressor How to & Troubleshooting Guide

In an air brake system, the air compressor supplies and maintains air under pressure to operate machines. That means that the compressor provides airflow for the entire system. That said, an air compressor’s effectiveness is affected by humidity, temperature, and atmospheric pressure. The Bendix air compressors are an excellent choice for people looking for a reliable air supply system. Bendix has been creating air brake and powertrain solutions for nearly a century.

All their products come with the knowledge and experience gained by the company in that time. Bendix manufactures both single cylinder and twin cylinder air compressors. The company endeavors to provide energy-efficient and reliable compressors. If you are looking to replace your air compressor, installing a Bendix air compressor is a great choice. It is, however, crucial to learn how it works and how to deal with any problems that occur. Here is a comprehensive guide to using a Bendix air compressor.

How does a Bendix air compressor work?

You need to know how a Bendix air compressor works before installing it. It is possible to identify problems in your compressor and fix them if you know how the system works. A vehicle engine drives the air compressor and keeps working as long as the compressor is working. The compressor has an unloading mechanism, and this, along with the governor, controls the air compression. The governor and the compressor helps maintain the brake air pressure. Here is how a compressor works.

  • A vacuum is created during the piston downstroke between the piston top and head, which causes the circular inlet valve to move from its position.
  • That draws air in, which flows into the cylinder.
  • During the upward stroke, the air is compressed, and pressure on the inlet valve and its spring return it to its seat.
  • Further compression on the upward stroke pushes the discharge valve from its seat.
  • The air flows past the discharge valve and into the reservoirs.
  • When the piston gets to the top of the stroke and begins moving downwards, the discharge line air pressure pushes the discharge valve into its place.  
  • That prevents compressed air from going back into the cylinder bore as more air is flowing in and the compression cycle starts again.

Why is my Bendix air compressor not working

If your air compressor stops working, there are several possible causes. Bear in mind that driving a vehicle with a compressor that is not working puts you and other motorists in danger. It is essential to identify the problem to fix it and get your Bendix air compressor working again. Here are some of the reasons that your Bendix air compressor is not working.

  • There is no electrical power, and you need to reset it or turn it on.
  • Low oil levels can also stop your compressor from working, which is why it is essential to check your oil regularly and increase the amount where necessary.
  • If the pressure switch will not make contact, that results in your air compressor failing.
  • A bad unloader valve will also stop your Bendix compressor from working correctly.

Is it ok to leave air in a Bendix compressor?

It is not advisable to leave air in your Bendix compressor because it affects compressor seal life and is a safety hazard. That said, a Bendix compressor comes with an unloader valve, which will release the air in the tank automatically.

Why does my Bendix air compressor take so long to fill

If your air compressor takes too long to fill, it could be a sign of a governor malfunction or a blocked discharge line. It could also be a sign of a heater malfunction and that your exhaust port has frozen open.

Governor malfunction

  • To test for governor malfunction, you will need to check the control lines and look for restrictions. If there are any problems, make sure that you make repairs.
  • Use the external gauge of the service reservoir, supply reservoir, or reservoir port to verify that the cut-out and cut-in pressures are in the vehicle’s original manufacturer’s specification. If they are not, you will need to make adjustments or replace the air compressor.
  • If the governor is malfunctioning, make sure that you replace it.

Air dryer heater malfunction

If the air dryer heater is malfunctioning, the best thing to do is replace it. When the air dryer does not work correctly, water pools, and if it freezes, it can damage it. Problems here can also result in water vapor mixing with oil, which can reduce the longevity of your compressor even more.

Compressor Malfunction

If the compressor is failing, you should replace it. That said, you should only replace the compressor if the above things are not an issue.

What happens if the compressor runs out of oil

Your engine provides oil for lubrication and cooling of the compressor parts. If your compressor runs out of oil, it will heat up very quickly.

  • Overheating can cause your Bendix air compressor to become too hot and shut down completely.
  • The oil provides lubrication to your Bendix air compressor. If your compressor runs out of oil, it will wear out quickly due to friction.
  • Your compressor is most likely to run out of oil if it leaks. Some of the reasons that your air compressor could leak include the following.
  • An overfilled compressor oil tank. If there is too much oil in your compressor, it will leak.
  • Damage to the reed plate or valve plate can cause your compressor to start leaking.
  • An air leak can also cause an oil leak.
  • If you do not have an air leak or visible oil leak, remove the head and inspect the valve plate and reed plate for damage.

How to check for an air leak

It is essential to check for an air leak in your compressor regularly. Air leaks cause oil leaks, which interfere with compressor performance and longevity, as shown above. To check for an oil leak, follow the following steps.

  • Shut off the engine and drain all air pressure from the vehicle.
  • Disconnect the inlet and remove the governor’s line or adapter fitting.
  • Apply liquid soap to the inlet port and apply 120-130psi of pressure to the unloader. Make sure that any leaks are not above 50sccm. Utilize 120-130psi pressure on the discharge port and put soap on the inlet port. Remember bubbles indicate loss of air, and any leaks should not exceed 20 sccm.  
  • If there is excessive leaking, make sure that you replace the damaged part with a genuine Bendix part to ensure it does not happen again.

How to maintain and care for your Bendix Air compressor

Your vehicle and every part of the vehicle require maintenance and care regularly. Appropriate maintenance ensures peak performance and that your machine serves you for a long time. The same applies to Bendix air compressors. Maintenance and care will ensure that it works properly for a long time. Here are tests to carry out every six months, 50miles, or 1800 operating hours depending on what occurs first.

Air Induction section

  • Inspect the engine air filters and air cleaner for dust and debris. Make sure you clean or replace air filters to ensure that your compressor only gets clean air.
  • Check the intake hose adapters on both sides for physical damage.
  • Inspect the intake hose clamps and ensure that they are tight enough.
  • Check the intake line for drying, chafing, or ruptures and have them replaced where necessary.

Compressor cooling system

  • Check the compressor inlet cavity, discharge line, and discharge port for restriction.
  • Make sure that you also check the system for carbon buildup. If there is more than 1/16″ of carbon, clean all the affected areas and make necessary repairs.
  • Sometimes carbon buildup is a sign of compressor cooling problems, so make sure you check the compressor cooling system. Check all the coolant lines for blockage and kinks and make necessary repairs and replacements.


Inspect the oil supply lines for restrictions and kinks and make the necessary repairs and replacements. Remember, as mentioned above, inadequate lubrication can lead to increased wear and tear on your engine.

Compressor drive

  • It is essential to check for noisy compressor operation, which is a sign of excessive drive component wear. Make the necessary adjustments or repairs if there is a problem.
  • Inspect the compressor drive system for leakage and ensure that the unloader mechanism works properly.

Compressor Governor and Unloader

  • Make sure that you test the unloader and governor for the correct pressure and operation. You can do that by following these steps.
  • Check for leaks around the unloader ports and replace worn-out or leaking o-rings.
  • Ensure the unloader system is connected correctly, as an incorrect connection can interfere with compressor performance.
  • Cycle the compressor through loaded and unloaded operation and ascertain that the governor cuts in at 105 psi and that the cut-out pressure is 15-20 psi more than cut-in pressure. If that is not the case, you need to replace or adjust the governor.
  • Ensure that the compressor cycles from unloaded to loaded without problems. If there are issues, make the necessary adjustments to the governor or replace it.

Cylinder head

  • Check for air leakage around the cylinder head gasket. You can use the following steps.
  • While the engine is running, lower the air pressure to 60psi and apply liquid soap to the cylinder head gasket.
  • Check the area for soap bubbles and make the repairs to the cylinder head or replace the compressor.

Why does the safety valve release air

If the safety valve releases air, it signals a restriction between the reservoir and air dryer or a malfunction in the air dryer safety valve. It could also be due to poor maintenance, a dryer malfunction, poor installation of the governor control line, or a governor malfunction.

  • Take the time to check the delivery lines to the reservoir for restriction and kinks. Make the necessary repairs immediately.
  • If you suspect an air dryer malfunction, ensure that the relief pressure is at the correct specifications.
  • Make sure that you regularly perform maintenance on your vehicle. You can do it every six months or every 50 miles to ensure that your compressor does not develop problems.
  • Check that the governor control line is installed correctly and in excellent condition. If it is not, carry out the necessary repairs.

Why does my compressor constantly cycle

If you notice that your compressor is constantly cycling and does not stop, it could be due to any of the following reasons.

  • The air brake system is not maintained correctly. Without proper maintenance, the reservoir may fill up with water, lowering its capacity. If this is the problem you are having with your Bendix compressor, drain and perform routine maintenance.
  • There could be a malfunction in the compressor loader mechanism. You will need to test the system for a leak, and if you find one, make sure that you repair it immediately.
  • Your compressor running nonstop could be caused by an air dryer delivery valve or purge valve malfunction. Make sure that you check the operation of the air dryer and carry out recommended maintenance.
  • An air brake system leakage could also cause your compressor to keep cycling. Use the following steps to test.
  • Park the vehicle on a flat area and chock the wheels. Build the system pressure until the governor cuts out and then let the pressure stabilize for a minute.
  • Watch the gauges on your dashboard for two more minutes without applying service brakes.
  • Apply brakes and wait for the pressure to stabilize. You can hold the pedal down using a woodblock.  
  • If you notice changes of up to 4 psi on the dashboard gauges, you have leaks, and you need to repair them immediately.

How do I know if my compressor is bad?

There are several signs that your compressor is not working accurately. If you experience any of them, you need to inspect your compressor and make the necessary repairs.

  • There is a problem with your compressor if it does not start. An old compressor may refuse to start, and you should replace it. If the compressor cannot achieve sufficient cut-in pressure, it will not start. The compressor not starting could also be due to problems in the pressure switch, motor, and unloader valve.
  • Another sign of compressor problems is when it keeps running and will not stop. That could be due to a faulty pressure release valve or pressure switch.
  • Odd noises, such as rattling or screeching, signal that something is wrong with your compressor. You may have electrical issues or a loose distributor motor.
  • Excessive moisture around your compressor system is another sign that your compressor is bad.