Oil getting into the refrigerator system is a serious technical malfunction that can lead to complete equipment failure. In normal operation compressor it must retain the lubricant inside its housing, ensuring the tightness of the circuit. However, if you notice oily spots on the evaporator or in the chamber, this is a signal of depressurization or a malfunction of the piston group.
The process of pumping out liquid requires accuracy and understanding of the physical processes occurring in a closed loop. Simply opening the tap and draining the contents will not work, since the system is under pressure and filled with refrigerant. You will need specialized tools, including vacuum pump a pressure gauge station.
Ignoring the problem or trying to solve it using “folk” methods without vacuuming often leads to expensive repairs with replacing the filter-drier and flushing the entire system with nitrogen. In this material we will analyze professional methods for removing lubricant from the circuit.
Causes of oil getting into the cooling system
The main reason for the migration of lubricant is a violation of the tightness of the piston group compressor. Wear of the rings or cylinders allows the oil, along with freon vapor, to escape into the discharge pipe. This is a classic symptom of unit aging, especially in models operating at high temperatures.
The second scenario is improper refueling or repairs in the past. If a technician fills in an excess amount of oil when replacing a compressor, excess liquid will inevitably be forced into the system. It is also possible to use an incompatible type of lubricant, which changes its viscosity and properties.
⚠️ Attention: If oil has entered the system due to compressor wear, simply pumping it out will not solve the problem permanently. After some time, the situation will repeat itself, since node defect it won’t go anywhere.
The third factor is long-term downtime of equipment. If there is no operation for a long time, the oil can flow into the evaporator, and upon startup it can suddenly boil and be carried away by the flow of refrigerant. In such cases, the correct defrosting and settling procedure often helps.
Necessary tools and preparation
To perform the work you will need not only desire, but also a specific set of tools. Without them, quality remove oil from thin capillary tubes is almost impossible. The basic kit includes a torch, wire cutters, pliers and a copper flaring tool.
A critical element is the presence of a nitrogen cylinder with a reducer. It is nitrogen that is used to purge the system and create the pressure necessary to push out the viscous liquid. The use of oxygen or air from a tire compressor is strictly prohibited due to the risk of explosion or moisture ingress.
You will also need the following consumables:
- 🧴 New filter drier (required after opening the circuit)
- 🔧 Pipe cutter and rolling tool set
- 🌡️ Manometric station with hoses
- 🔥 Gas burner with solder
Before starting work, the refrigerator must be completely defrosted and dried for at least 24 hours. Any moisture inside the circuit will turn into an ice plug during operation, which will block the circulation of freon.
Methods for removing oil from the circuit
There are several methods for cleaning the system, the choice depends on the degree of contamination. If there is not much oil, sometimes purging with nitrogen high pressure is enough. The technician connects the cylinder, creates a pressure of about 15-20 atmospheres and sharply opens the valve so that the air wave knocks out the liquid.
A more radical method is flushing the circuit with liquid refrigerant or a special solvent (for example, freon R141b, although its use is now limited eco-standards). The liquid is poured into the system, shaken and drained along with the dissolved oil. This process is repeated several times.
The most reliable, but labor-intensive method is to dismantle the heat exchangers. The evaporator and condenser are removed and washed separately in a bath of solvent. This guarantees the removal of 99% of contaminants, but requires a complete re-rolling of all connections during assembly.
Why can’t you just pour out the oil?
The oil in the refrigerator is not in one place, like water in a glass. It is distributed along the walls of thin tubes of the capillary and evaporator in the form of a film. Therefore, mechanical leakage is impossible without creating pressure or using solvents.
Step-by-step instructions: pumping and flushing
Start by disconnecting the device from the power supply and accessing the back wall. Cut off the compressor filler tube to release any remaining pressure. Then you need to unsolder the filter drier and condenser from the compressor.
The next step is the washing procedure. Connect the nitrogen hose to the condenser and apply pressure. At the exit from the capillary tube, you will see oil begin to fly out under the pressure of the gas. The process is continued until clean gas without oil inclusions comes out of the tubes.
For complex cases, the “counterflow” method is used. Nitrogen is fed in the opposite direction through the capillary to dislodge contaminants from the condenser. This requires care so as not to damage the thin walls of the tubes with excess pressure.
☑️ Checklist for flushing the system
Table: Types of oils and their compatibility
When changing oil or refilling, it is critical to use the correct type of lubricant. Mixing different bases (mineral and synthetic) can lead to the formation of a dense sediment that will permanently clog the capillary tube.
| Refrigerant type | Oil type | Features | Hygroscopicity |
|---|---|---|---|
| R12, R134a | Mineral | Classic base, cheap | Low |
| R134a | Polyester (POE) | Used in modern models | High |
| R600a | Mineral / Alkylbenzene | Works with isobutane | Medium |
| R404A, R507 | Polyester (POE) | For industrial cold | Very high |
Pay attention to the hygroscopicity of synthetic oils. They absorb moisture from the air in literally minutes. Therefore, jars of oil polyester type cannot be kept open for longer than 15-20 minutes.
⚠️ Attention: Never mix mineral oil with polyester oil (POE). This will lead to a chemical reaction and precipitation, which will destroy the compressor.
Replacing the filter and vacuuming
After you have managed to expel the bulk of the oil, you need to install a new filter drier. This element collects residual moisture and microscopic particles of dirt. The old filter cannot be used after flushing the system - its sorbent is already saturated.
Assembling the circuit is completed by soldering the connections. The next stage is vacuuming. Connect the vacuum pump to the system and turn it on. The process should last at least 30-40 minutes. The pressure gauge should show a deep vacuum (about -1 bar or 29.9 inHg).
A vacuum is necessary to remove water and air vapor. If you skip this step, the remaining moisture will freeze in the capillary, causing an “ice jam,” and the refrigerator will stop freezing. After evacuation, the system is charged with the calculated amount of refrigerant.
Common mistakes during repairs
The most common mistake is trying to flush the system by simply opening the accessible tubes and blowing into them with your mouth or a household compressor. A pressure of 2-3 atmospheres is not enough to push viscous oil through a narrow capillary. Professional equipment is required.
The second mistake is ignoring the filter replacement. Even if you drove out the oil, acid radicals and moisture remain in the system, which will kill the new compressor in a couple of months of operation. The filter is the “kidney” of the refrigerator; they are always changed.
The third mistake is the use of inappropriate solvents. Acetone or alcohol can dissolve the oil, but they can also damage the internal insulation of the compressor motor windings or react with the tube material.
Is it possible to completely remove oil from the evaporator?
Completely, 100%, remove oil from the thin evaporator tubes without dismantling and washing in a bath practically impossible. However, professional high-pressure nitrogen purging allows you to remove up to 90-95% of contaminants, which is an acceptable standard for further work.
How much oil should be in the compressor?
The volume of oil is strictly regulated by the manufacturer for each model. Usually it is from 200 to 400 grams. Excess oil is just as dangerous as its lack: excess reduces the efficiency of heat transfer, and insufficient leads to jamming of the pistons.
Do I need to flush the system if I change the compressor?
Yes, if the old compressor burned out or was leaking oil into the system. Flushing is mandatory, otherwise the new unit will instantly become clogged with decay products of old oil and metal shavings.
What is dangerous about mineral oil in the R134a system?
Mineral oil is poorly soluble in R134a freon. It will settle in the heat exchangers, creating an insulating film, which is why the refrigerator will stop gaining temperature, and the compressor will work without stopping.
How to understand that oil has entered the system?
Main signs: decreased cooling efficiency, the presence of yellowish spots on the walls of the chamber or evaporator, unusual hum of the compressor. In advanced cases, oil can be seen in the sight glass (if there is one) or at the outlet of the capillary.