Oil is not supposed to be in the truck air brake system, but sometimes it appears; what causes oil in the air brake system?
If oil is found in the air brake system line, it is due to faulty compressor piston rings, overfilled compressor oil, or a faulty air dryer.
The day I discovered oil in the truck brake line, I conducted a lot of troubleshooting.
I noticed the air compressor piston rings had worn, so I replaced the worn piston ring.
I still have some informative articles on air brake systems.
Keep reading below for more details.
What Causes Oil In Truck Air Brake System
The vehicle’s compressor takes in filtered air, either from atmospheric pressure (or increased pressure, in some cases from the engine’s turbocharger) or turbocharger, and compresses it.
The air dryer receives the compressed air and uses it to remove water and a tiny quantity of oil.
The air then travels to the air tanks (“air tanks”), which are delivered to the rear brake system tank, the front brake system tank, and the tanks on the trailer.
Therefore, the system should be oil-free to enjoy maximum air brake system.
These are the 3 reasons for oil in the system.
1. Worn compressor piston rings: This is the most common reason why oil is in the air brake system. Oil is in the compressor to provide lubrication.
The piston rings provide sealing so the oil and compressed air do not escape.
However, when the piston rings wear, the end gap becomes wider, and the oil escapes to the top of the piston.
2. Overfilled compressor oil: If there is too much oil in the crankcase of the air compressor, the oil will force its way to escape through the piston rings’ end gap.
As a result, the oil will get to the line of the air brake system.
3. Faulty air dryer: The air dryer removes liquid from the air compressor discharge so that dry compressed air is stored in the air reservoir.
But when the air dryer is faulty, it allows oil to get to the reservoir, which in turn gets to the brake.
How Does Moisture And Oil Affect Car Air Brake Systems
One of the most dangerous faults in a vehicle is brake failure because it usually results in an accident or a loss of life.
Oil and moisture in the air system can cause a freeze in cold weather, leading to brake failure.
That is why you must drain the air tank and avoid oil in the brake line.
When liquid is present in the air brake system, it can cause a freeze in the line, which would obstruct the air movement in the system.
As a result, there will be brake failure.
In the winter, any moisture trapped in the system can cause freeze-ups. In the summertime, gunk and debris can clog up the system.
Some air dryers have desiccant cartridges that absorb moisture.
These cartridges can become too contaminated to function properly and must be replaced.
Why Is My Air Compressor Leaking Oil From The Bottom
The most common reason for oil leakage from the bottom of the air compressor is a worn oil seal or gasket.
It depends on how the air compressor was designed; some use a gasket, while some use an oil seal. If the gasket or the oil seal is worn, it will cause oil leakage at the bottom of the air compressor.
That is what happens to my Mack truck air compressor. I noticed oil drops from the truck, so when I traced the leakage, I found it was from the air compressor.
After much effort, I discovered the leakage’s source: the worn seal.
I went to a shop where I bought the seal, and I replaced the seal, and the leakage stopped.
Another point you need to note is the oil level. Ensure that the oil does not exceed the gauge level, as this can cause oil leaks.
Can A Leaking Compressor Be Repaired
As mentioned above, a leaking compressor can be repaired. It can leak air or oil.
Whether the compressor leaks air or oil, it can be repaired.
If the leakage is oil, you must replace the oil seal and the gasket.
These are the common causes of oil leakages in the air compressor.
But if the leakage is from compressed air, then you have to check the fittings and the pipe for leaks.
Air pipes and fittings are prone to leaks, especially when there is breakage along the line.
A damaged head gasket of the air compressor can be responsible for leakages in the. If you notice that, replace the head gasket.
What Is The Function Of An Air Dryer In Truck Air Brake System
Draining accumulated water from air tanks was an everyday task many years ago.
Fortunately, water is absorbed by the air dryer, reducing its effect on system components.
Normally, we would expect to see little, if any, water draining from the purge valve.
If you see water, it could indicate that you need to replace the air dryer.
A little oil is expected to pass through the bleed valve. Oil enters the airlines during normal operation.
That only becomes a problem when the oil starts to mix with water vapor. The result can:
Affects air discharge cycles.
Blocking the purge valve and causing a constant leak
Coating the media of the air dryer media and reducing its effectiveness
Build-up in air lines and valves, decreasing the life of system components.
In summary, air dryers remove oil and water(moisture )from the airline.
How Would Leaky Oil Rings Affect A Compressor
Leaky oil rings affect the compressor by reducing its compression.
For the compressor to produce air, the oil rings should be able to provide a seal against the compression going downward.
When the oil rings are bad, compression escapes from the end gap of the rings, and such a compressor lacks the needed power to produce sufficient air.
In addition, leaky oil rings cause the compressor to produce wet compressed air because they allow oil to mix with the air.
If a compressor oil ring is not repaired, it will wear other components, such as the piston and sleeve.
What Happens When You Put Too Much OIL In A Compressor
It is important to ensure that your air compressor is always running at the proper oil level to keep it running as efficiently as possible.
On the other hand, completely filling the oil sump on your compressor might seriously harm its internal components.
When excess oil is aerosolized by compressor discharge, it can cause damage not only to your compressor but any air tools and accessories attached to it.
Oil discharge can also ruin your final product, sometimes to the point where the products must be scrapped and remade entirely.
Any spray painting, sanding, or application of finishes would be ruined due to oil entering the airstream.
With preventative maintenance, you will greatly reduce the risk of projects being ruined by oil interference in your compressor’s airstream.
What Causes Moisture To Form In Truck Air Brake System
Atmospheric air, containing impurities and water moisture, is drawn in by the compressor and compressed to a higher pressure.
Compressors require oil for lubrication, sealing, and cooling.
Upon completion of compression, hot compressed air flows to the aftercooler to remove the heat produced by compression.
During the cooling process, the air loses its ability to contain much water; an excessive amount of water and water vapor is removed as a liquid (condenses).
The air is additionally cooled in the pipes and dryers, where additional condensation occurs.
The condensate drain is the most overlooked component in a compressed air system but is nevertheless very important.
No matter how much money is wasted on high-quality compressed air equipment (compressors, dryers, filters), air quality is worthless if condensate is not discharged.
Final Thought
Excessive oil in the compressor, damaged compressor rings, and a faulty air dryer are reasons for oil in the air brake system.
Moisture and oil in the air system cause brake failure because they can freeze and obstruct the air pipes.
The air dryer ensures that the air is free from all liquids, including moisture and oil.
The process of compressed air cooling down forms moisture, so draining and purging help to remove it from the air system.
Remember the importance of maintaining an accurate oil level.
Overfilling the compressor will cause issues for both the compressor and the brake.
Why not read one more article on air brake systems.