How to Drain AC System Car – Useful Guide

It is important to drain your car’s AC system. Today’s car owners must understand many things about the construction of the vehicle, from the brake discs to the wipers. Otherwise, he will be forced to spend a large sum on car service.

It is clear that some types of repairs can only be performed by an experienced auto mechanic. It is vital to understand how to drain ac system car in order to maintain your car.

It necessitates the use of specialized equipment, such as vacuum pumps, air conditioning recovery units, and low-pressure manifold gauges, as well as strict adherence to OEM-recommended protocols. The entire procedure takes 30 minutes to an hour to complete.

Read on to find out how to flush your car’s air conditioning system.

How an AC System Works

Your car’s AC system is similar to the one in your house. Air flows through refrigerant-filled coils. As the refrigerant continues to flow, the temperature of the air fluctuates. After all, the air in your automobile originates via the vents.

Refrigerant is constantly cycled and pushed through an air conditioning system. It undergoes compression, evaporation, and condensation cycles. The cycle is totally closed, which means no fresh refrigerant is required it is just reused.

When the car’s AC system needs to be drained

Let’s list the cases when you need to drain the car’s AC system coolant.

1. The coolant properties have changed

This can be caused by oxidation, temperature fluctuations, and evaporation. Refrigerant normally retains its performance properties for three years. After this time, the coolant should be drained.

2. Water or other liquid was added to the refrigerant

It also happens that after the refrigerant boiled (or you made the repair yourself), you needed to refill the coolant, but you did not have the right composition with you. You had to add water or refrigerant from another brand. After such manipulations, it is necessary to drain the coolant and pour in new coolant.

3. In the case of Repair

Did you have to drain the coolant during the repair work? Specialists advise in this case to fill with new refrigerant, especially when the old liquid has been used for more than two years. It is not allowed to mix the old and new coolants otherwise, its performance properties will change for the worse.

How to drain car AC system completely

In most cars, it is necessary to go through several steps in order to drain car AC system. This is because the engine cooling system, in which the coolant is poured, consists of many communicating cavities: nozzles, valves, heaters and engine radiators, engine blocks, thermostats, and so on.

Precautions to take while working with automobile coolants

Beware of contact with the coolant on exposed parts of the body and the eyes. It is forbidden to drink it, as it is made from ethylene glycol, which is the strongest poison. The fact is that it tastes sweet, so keep the technical fluid out of the reach of children. When replacing the fluid, make sure that it does not get on the soil.

What consequences can arise

Vehicles are often serviced using specific fluids, such as refrigerant. The degradation of such compositions is caused by regular vehicle use. This is frequently what causes the foam to form in the system. As a result, corrosion forms not only in the cylinder block but also in the radiator and thermostat.

But that isn’t the worst of it. Foam formation may be the primary cause of cylinder block failure. A significant repair is necessary for this scenario. Not every automobile owner understands how to remove the coolant from the system. As a result, it is worthwhile to go deeper into this topic.

Requirements for draining the AC system

  • Gloves and safety glasses. (Gloves will save you from accidentally contacting hot metals on your vehicle.)
  • Pancake air compressor. (There is just no way to empty your car AC system without the compressor.)
  • A bucket.
  • Vacuum Pump. (releases all air from the recovery tank)
  • AC Flush gun. (A flush gun is required. Before proceeding, ensure that you have this.)
  • Flushing solvent. (Flushing solvent is sprayed through car AC components after being put into the flush gun.)

How to drain a Car AC System: Step by Step

This manipulation should be performed when the motor is cold. Otherwise, burns may occur. It takes 30 minutes for the machine to cool down after it has been switched off.

Follow the steps below to completely drain your car’s AC system. Make sure to read these steps before starting so you know what to expect.

1. Prepare a recovery tank

Open the valves and release the nitrogen in the recovery tank to prepare it.

2. Connect the vacuum pump

Remove air and moisture from the recuperator tank by attaching a vacuum pump to its blue expansion valve. Make sure that the valves of the recovery tank are closed.

Then turn on the vacuum pump while opening the blue access valve. Leave the vacuum pump on for about an hour to remove all air and moisture from the regeneration tank.

3. The hose should be connected to the evaporator outlet

The evaporator is located near the back of the engine bay. You should be cautious about the port leading to the compressor. Remove the connection to reveal a metal pipe with threaded outlets.

Keep an eye on the hose as you progress through this stage if it is large. If it breaks free, the refrigerant will leak into your engine bay, causing a commotion in your garage.

4. Insert the car AC system hoses on opposite ends in an empty pail

The opposite end of the rubber hose must be placed in an empty bucket. This is where you will blow out any remaining refrigerant and debris.

To make the process easier, the bucket and hose should be placed on the ground. Because the technique is performed on the port’s downhill side, when you complete spraying, the refrigerant will not flow back into the hose.

5. Wait for a while

It may take a few minutes to equalize the low pressure in the car’s AC system after that. After all, you’ve just recently subjected the system to air pressure.

6. Use the evaporator flush gun

Allow the evaporator inlet to be viewed next. You have not yet touched the second and last outlet. The refrigerant enters the intake first, before passing through the evaporator and into the compressor.

Instead of putting a rubber hose around the inlet pressure port, insert the flash gun nozzle into the inlet port at this stage. Before you begin, make sure the flushing pistol has enough flushing solution.

Turn on the compressor and squeeze the flushing gun trigger once everything is put together. Carry ahead with the process for the condenser.

Impurities may be hidden in the evaporator’s many corners, and stopping early will only enable those contaminants to recirculate when you’re finished.

Remove the flushing gun and hose from the outlet once you’re finished flushing. Do not remove the fittings because they will be cleaned in a few stages.

7. Repeat the previous step for the Condenser

After finishing the evaporator, you may go on to the condenser.

This will be the engine bay component directly in front of your car’s grille. Place yourself so that you have a clear view of the inlet and easy access to it.

Take out your a/c flush gun and top out the flush solution as needed. Before turning on the compressor, make sure the connection between the pancake AC compressor and the flush gun is secure.

With these ports exposed, connect the same hose to the outlet and run the other end into the same bucket.

8. Unplug and flush the liquid line

A liquid line will transport the refrigerants in your car’s AC system. A close-up of the automobile’s fluid line This line does not need to be replaced simply reconnect it after emptying it.

As a result, I would recommend eliminating the liquid line. It should only have a threaded pipe fitting on each end, making removal simple with an adjustable wrench.

You do not need to replace this line simply reconnect it after emptying it. It’s a metal line, as opposed to the rubber lines that run everywhere else. It is commonly seen around the batteries.

Take a moment to examine the line. If any of the insulation is ripped or you observe pits from corrosion, you’ll need to replace this liquid line. If everything appears to be in order, clean the line before reinstalling it on your vehicle.

9. Flush Each Hose Removed

Each hose of the car AC system may include refrigerant. Drain the refrigerant from each of these hoses before installing the evaporator and condenser.

It is critical to know where each hose originates. Because they are likely different lengths, they can only be joined in a certain way.

If there is an additional hose near the car AC system compressor, it should be removed and cleaned as well. You haven’t touched the compressor in any way, so you’ll have to locate it and disconnect the additional hoses.

Before reinstalling the system, any cracked or broken hoses or fittings should be replaced. Your HVAC system will cease supplying cool or hot air if your air conditioning system leaks.

10. Place everything in its proper location

By the conclusion of this cycle, you should have numerous clean, disassembled pieces. Everything that you demolished must be reinstalled.

Begin with the air conditioning hoses and fluid lines. Check that they are snugly pressed into each pressure port. The high pressure can blow them out and cause a leak if they are even slightly loose.

Standards for high and low-pressure ports in the car ac system

The low pressure should be near 30 PSI at 90° F or less. Excessive low pressure or higher shows there is a problem. On a properly working system, high pressure will be about twice the ambient temperature, plus 50 PSI.

Excessive high and low pressure is quite dangerous. Air conditioner compressors are only intended to work within a certain temperature range. Higher than usual pressure will distort the metal shell and render the compressor inoperable very soon.

High pressure will also cause an evaporator coil leak. This may be highly expensive because you frequently have to remove the dashboard to address the problem.

When this step is completed, your AC system should be fully built and ready for filling.


How do I evacuate my car AC without a pump?

A vacuum pump is a preferable option for a car AC system flushing, but it is not the only one. Here are a few alternatives for emptying a car AC system without a pump.

To make your own vacuum pump, use an old refrigerator with a good AC compressor and hoses.

Installing an access valve on both the low and high-pressure ends of the system is another technique to evacuate your car’s air conditioning system.

How do you evacuate an AC system in a car?

A vacuum pump is a superior option for an AC evacuation, but it is not the only one.

Begin by unplugging the air conditioner and flushing all tubes, the condenser, and the evaporator. Reconnect everything, and inspect each step for damage. Fill the line via the low-pressure port with refrigerant until the system is full, then check to see whether the air conditioner is blowing cold air.

How do you drain refrigerant from the car AC system?

To start the process of draining the refrigerant, you must remove the car’s engine guard system by unscrewing the four bolts.

Turn the heater temperature regulator to the right up to the stop, setting the strongest heating. If the car is equipped with automatic air conditioning, then its switch is also set to maximum. Unscrew the cap on the expansion tank or leave it screwed—each driver decides for himself.

If you unscrew it, it will be possible to completely drain the coolant quickly.

Fill your line via the low-pressure port when you have enough refrigerant in your car’s AC system, and check to see whether the car’s AC system is blowing chilly air.

Keep in mind that in this case, the coolant can splash, and the drops will get on the car’s engine.

How much does it cost to drain the AC system in a car?

Evacuating your AC system is almost free if you have manifold gauges, a vacuum pump, an AC recovery machine, and a recovery tank. However, if you ask a professional to take over, you may be charged the following fees:

A drained AC system may cost anywhere from $80 to $370 depending on the size of your vehicle and whether you go to an independent technician or a dealership.

Video: How to Drain AC System Car

In this video, you can watch how to evacuate your car’s AC system the right way. It is demonstrated on a BMW 435i F33, but this will work for any modern vehicle AC System.

Final Thoughts

To deal with the question of how to flush the cooling system of the car engine and how the cooling radiator in the car affects the functionality of all units is easy enough.

For practical reasons, whenever you repair a faulty air conditioning system, you should always flush it. If you do not cleanse the air conditioning system, acids generated by the high-temperature interaction of moisture and refrigerant will harm various sections of your car.

As part of the cleaning process, both car chemicals and domestic treatments are employed. And, in order to avoid cleaning too frequently, it is important to change the refrigerant on a regular basis.

Knowing how to drain the AC systems and replace the refrigerant, you can do this easy task yourself and save money on a car repair appointment. Here is how to install a truck tool box without drilling.

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