Does Evacuating AC Remove Oil? A Friendly Guide to Understanding the Process

Air conditioning systems have a crucial role to play in maintaining a comfortable temperature in our vehicles and homes.

However, over time, the AC system can accumulate moisture and debris, which may affect its performance.

Evacuating the AC system is an essential step in maintaining and repairing air conditioning units.

This process goes a long way in removing moisture, debris, and other contaminants from the refrigerant lines.

Does Evacuating AC Remove Oil

Does Evacuating AC Remove Oil?

So, does evacuating the AC system also remove the oil within it? The short answer is no.

The oil used to lubricate the compressor and other components of an air conditioning system is not removed during the evacuation process.

The oil is crucial for proper functioning, ensuring smooth operation and preventing premature wear of components within the AC system.

Despite removing most contaminants, airflow is limited during this process, which prevents the removal of oil.

Let’s get a deeper insight into this aspect through this comprehensive guide.

Reasons for Evacuating AC System

  • Moisture removal: Evacuating the AC system helps remove moisture from it, ensuring better performance and preventing corrosion.
  • Air and contaminants: It removes trapped air and contaminants that can reduce system efficiency and lead to damage over time.

Procedure for Evacuating your AC

  1. Turn off the car: Make sure the car engine is turned off and the AC system is in a resting state.
  2. Access AC components: Locate the high-pressure and low-pressure ports in your car’s AC system.
  3. Connect gauges and vacuum pump: Attach AC manifold gauges to the high-pressure and low-pressure ports, and connect a vacuum pump to the manifold’s center port.
  4. Begin vacuum: Turn on the vacuum pump and allow it to run for about 30 minutes. Monitor the gauges during this process.
  5. Inspect for leaks: After the vacuum process, hold the system at the vacuum level for 15-20 minutes and observe if the vacuum holds.
  6. Close the valves and turn off the pump: If the vacuum holds, close the high-pressure and low-pressure valves on the manifold gauges and turn off the vacuum pump.

While evacuating the AC system eliminates moisture and contaminants, it doesn’t remove oil.

Oil may seep out during the refrigerant evacuation process but replacing it requires proper filtration.

Moreover, running a car without oil even for a few seconds can be dangerous.

Reasons for Oil Removal

  • Wear and tear: Over time, AC oil can become contaminated, leading to reduced system efficiency.
  • Leakages: Leaks in the AC system can result in low oil levels and decreased performance.
  • Component replacement: When replacing certain AC components, it’s necessary to remove old oil.

Procedure for Oil Removal

  1. Evacuation: To remove moisture and contaminants, first evacuate the AC system.
  2. Flushing: Use an AC flush solvent to clean the system, removing any residual oil and debris.
  3. Draining: Drain excess solvent and old oil from the components.
  4. Refilling: Add the appropriate amount of PAG oil to the system, ensuring proper lubrication and optimal performance.

Table comparing PAG oil and Mineral oil

ComparisonPAG OilMineral Oil
Moisture AbsorbHighLow

Note: The procedure for oil removal may vary, depending on the AC system type and specific requirements. It’s crucial to follow the manufacturer’s guidelines for proper oil level maintenance.

Effects of Moisture and Non-Condensable Gases

One common issue in AC systems is excessive moisture. It can cause various problems such as reduced efficiency, corrosion, and even system breakdown.

Identifying Moisture Issues

  • Visible signs: Condensation or frost on piping, dripping water from components
  • Hidden issues: Corroded expansion valves, failure of compressor

Impact of Non-Condensable Gases

Non-condensable gases (NCGs) are gases that do not readily condense even at normal temperatures and pressures found in AC systems. Common examples include air and nitrogen.

When present, NCGs have negative impacts:

  • High head pressures: Increases the work needed by the compressor, causing it to run hotter
  • High discharge temperatures: Leads to higher electricity consumption and potential damage to components
EffectMoistureNon-Condensable Gases
Component wear and damageAccelerated due to corrosionintroduced by NCGs
System breakdownPossible due to valve failuresPossible overheating

Understanding and addressing moisture and non-condensable gas issues can help ensure optimal AC system performance and prevent costly repairs.

Compressor and Other Components

AC Compressor Function and Failure

The AC compressor plays a crucial role in your car’s air conditioning system. It pressurizes the refrigerant, allowing it to absorb heat from the cabin.

Compressor failure can occur due to various reasons such as leaks or overheating. Signs of compressor failure may include:

  • Poor cooling performance: The cabin doesn’t cool effectively.
  • Loud noises: Grinding or squealing sounds when AC is turned on.

Important AC System Components

  • Condenser: It dissipates heat absorbed by the refrigerant, turning it from a high-pressure gas into a high-pressure liquid. Located in front of the radiator, it requires a working condenser fan motor to maintain airflow across the condenser coils.
  • Expansion Valve: The expansion valve regulates the flow of the refrigerant, ensuring the right amount reaches the evaporator while maintaining proper pressure levels. It helps in cooling the cabin efficiently.

Comparison Table:

ComponentFunctionPotential Issues
CompressorPressurizes refrigerantLeaks, overheating, poor cooling, loud noises
CondenserDissipates heat, turns refrigerant into high-pressure liquidBlocked airflow, damage to condenser coils, condenser fan motor failure
Expansion ValveRegulates refrigerant flow and pressureClogs, malfunctions, resulting in poor cooling efficiency

Therefore, the compressor and other AC system components work together to provide efficient cooling for your cabin. Proper maintenance is necessary to ensure they continue functioning effectively.

Repair and Maintenance

Preventive Maintenance Tips

  • Regularly clean filters to ensure optimal performance.
  • Check for and seal any leaks in ducts to prevent energy loss.
  • Inspect refrigerant levels for maintaining heat transfer capability.
  • Monitor thermostat settings for efficient cooling and energy conservation.

Common AC System Repairs

  • Fixing refrigerant leaks: Leaks harm the environment and reduce AC efficiency.
  • Dealing with frozen coils: Can result in poor air circulation and system failure.
  • Replacing faulty fans: Ensures air movement through the AC system.
  • Repairing electrical components: Prevents hazards and maintains the AC’s performance.
Fixing refrigerant leaksEnvironmentally-friendlyTime-consuming
Dealing with frozen coilsPrevents long-term issuesTemporary disruption of service
Replacing faulty fansEnsures optimal air circulationMay require professional assistance
Repairing electrical componentsAvoids hazards and malfunctionsSafety concerns and expert knowledge needed

Essential Tools Needed

To evacuate an AC system and remove oil, you will need the following tools:

  • Vacuum pump: Designed for refrigerant evacuation, ensuring a clean and dry AC system.
  • Manifold gauges: Allow safe monitoring of system pressures.
  • Hoses: For connecting the manifold gauges to the AC system.
  • Nitrogen: Used for pressure testing and system flushing.
  • Recovery machine: To remove old refrigerant from the system.
  • Degassing equipment: Removes trapped air and moisture in the system.

Proper Use of Equipment

Using the essential tools properly is crucial for a successful AC evacuation. Here’s a short guide on how to use the main equipment:

  • Vacuum pump:
    1. Connect the pump to the manifold gauges using appropriate hoses.
    2. Attach the gauges to the AC system’s low and high-pressure ports.
    3. Start the vacuum pump and open the valves on the manifold gauges.
    4. Evacuate the system until it reaches a vacuum level of around 500 microns.
  • Manifold gauges:
    1. Connect the hoses to the low and high-pressure ports on the AC system.
    2. Ensure valves are closed before connecting to the vacuum pump or nitrogen tank.
    3. Open the valves to read pressure levels and control the flow of refrigerant or nitrogen.
  • Using nitrogen for flushing:
    1. Close the manifold gauges’ valves and disconnect hoses from the vacuum pump.
    2. Connect the nitrogen tank to the manifold gauges using a nitrogen regulator.
    3. Open the nitrogen tank valve and slowly open the manifold gauges’ valves.
    4. Allow nitrogen to flow through the system, flushing out old oil and contaminants.
Vacuum pumpEfficiently removes moisture and airCan be expensive, especially high-end models
Manifold gaugesAccurate pressure readings, easy to useMay require calibration for accurate readings
HosesEssential for connecting equipmentQuality varies, may cause leaks if not properly maintained
NitrogenEffective for system flushingRequires proper handling and storage
Recovery machineEfficiently removes old refrigerantExpensive, may require professional assistance
Degassing equipmentRemoves air and moistureAdditional expense, may not be necessary for all situations

It’s essential to properly use these tools and equipment to evacuate the AC system, remove oil, and ensure optimal performance.


In summary, evacuating an AC system does not remove oil, as the process focuses on eliminating air and humidity.

To extract oil from a car’s AC system, specialized solvents and cleaning methods are required.

The importance of maintaining proper oil levels in the AC system should not be overlooked.

Efficient functionality, component protection, and optimal performance are ensured through balanced oil quantities.

Frequently Asked Questions

How to remove PAG oil from AC system?

To remove PAG oil from an AC system, you’ll need to perform an evacuation using a vacuum pump.

This process will remove the refrigerant and oil from the system, ensuring a clean start for your next AC service.

How to inject oil in AC system?

Injecting oil into an AC system can be done using an oil injector. The injector is attached to the low-pressure side of the AC system, and the required amount of oil is added.

Always refer to your vehicle manufacturer’s guidelines for the correct amount of oil needed.

AC oil recovery process?

The AC oil recovery process begins with the removal of the refrigerant using a recovery machine.

The machine then separates the oil from the refrigerant, allowing you to accurately measure and replace the oil in the system during service.

How to get oil out of ac compressor?

To remove oil from an AC compressor, you need to evacuate the system using a vacuum pump or recovery machine.

This will remove the refrigerant and oil from the compressor, ensuring it’s empty before you start servicing or replacing it.

Do I add oil to new ac condenser?

No, you do not typically need to add oil to a new AC condenser. However, make sure to consult the manufacturer’s instructions related to your specific model.

Running AC compressor without oil, what happens?

Running an AC compressor without oil can cause it to seize or become severely damaged.

The compressor relies on oil for lubrication and cooling; without it, the metal components will grind together, leading to permanent damage and poor performance.

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Sean Mendez

Hi, I am Sean, a self-confessed petrolhead. I live in Boise, Idaho with a busy family of four and our energetic Labrador retriever. Thank you for visiting my website. You can find my email on the contact page.

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