10 Common Causes of Oil Leakage in Air Compressors and How to Fix Them

Oil leakage in screw air compressors is a frequent issue that affects performance and increases maintenance costs. If not resolved, it can lead to higher oil consumption, contamination of compressed air, and system failure. Below are 10 common causes of oil leakage in air compressors along with effective solutions to fix them.

1. Overfilling of Screw Oil

🔍 Cause: Adding too much screw oil increases the liquid level beyond the upper limit, reducing the efficiency of the oil separator and causing excessive oil content in the compressed air.

✅ Solution:

• Check the oil level when the compressor is turned off.

• Ensure the oil level is between the upper and lower scale lines on the oil sight glass.

2. Poor-Quality Screw Oil

🔍 Cause: If the oil has poor defoaming properties, excessive foam can enter the oil separator, increasing the oil content in the compressed air.

✅ Solution:

• Replace the oil with high-quality screw oil from the manufacturer.

• Always use OEM (original equipment manufacturer) oil to prevent foaming issues.

3. Mixing Different Brands of Oil

🔍 Cause: Using different types of engine oil can cause gelation or deterioration, leading to oil separator blockage and excessive oil discharge.

✅ Solution:

• Drain the system and replace the oil separator core.

• Clean the oil circuit and refill with a single-brand, high-quality oil.

4. Low Operating Temperature and Condensation Issues

🔍 Cause:

• If the exhaust temperature is lower than the pressure dew point, water vapor condenses into liquid, contaminating the oil.

• Over time, this can cause rust, bearing wear, and oil leakage.

✅ Solution:

• Drain small amounts of condensed water periodically and increase exhaust temperature.

• If water contamination is excessive, replace the oil, oil separator, and oil filter.

• If the rotor is rusted and abnormal vibrations occur, repair the compressor head.

5. Improper Air Pipeline Installation

🔍 Cause:

• After shutdown, condensed water flows back into the air compressor.

• If water enters the minimum pressure valve, it can cause oil separator flooding and oil leakage.

✅ Solution:

• Consult a professional to redesign the air pipeline.

• Follow Solution 4 for draining and maintenance.

6. Return Oil Pipeline Issues

🔍 Cause:

• Poor installation, blockages, or leaks in the return oil pipeline prevent oil from flowing back properly, forcing it out with compressed air.

✅ Solution:

• Inspect the return oil pipeline and check valve.

• Adjust or replace any damaged or improperly installed parts.

7. Undersized Compressor or Increased Air Demand

🔍 Cause:

• If air consumption is greater than the compressor’s rated capacity, the exhaust pressure drops.

• This increases the air velocity, reducing the efficiency of oil separation and causing high oil content in compressed air.

✅ Solution:

• Ensure the compressor size matches the air demand.

• Check for leaks in air supply pipelines and repair them.

• Add more compressors if necessary to meet demand.

8. Minimum Pressure Valve Failure

🔍 Cause:

• A weak or aging spring in the minimum pressure valve can lower the opening pressure, causing low exhaust pressure and oil leakage.

✅ Solution:

• Check the minimum pressure valve and adjust the spring tension.

• Replace the valve if needed.

9. Use of Low-Quality Oil Separator or Air Filter

🔍 Cause:

• Using inferior oil separator cores results in poor oil separation.

• Mismatched oil separator cores (wrong type, pressure rating, or size) reduce efficiency.

• Dirty or blocked air filters cause oil contamination.

✅ Solution:

• Always use OEM oil separator cores and air filters.

• Perform regular maintenance and replace filters as needed.

10. Post-Processing Issues

🔍 Cause:

• If precision filters are not correctly installed or are used beyond their lifespan, they may contribute to oil carryover.

✅ Solution:

• Select a proper precision filter for your system.

• Replace the filter elements on schedule.

Final Thoughts

🔧 Oil leakage in air compressors is often caused by overfilling, poor oil quality, pipeline issues, low operating temperatures, and improper maintenance. Regular inspections, using high-quality oil and filters, and ensuring proper system design can prevent leaks, extend compressor life, and improve efficiency.

Tip: If persistent oil leakage occurs despite troubleshooting, consult a professional technician for further diagnosis.

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