What to Do If the Car Air Conditioner Low-Pressure Pipe Is Leaking Oil?
4 Answers
If the air conditioner joint is leaking refrigerant, a small amount of compressor oil may also come out with it. It is necessary to check whether the copper pipe flare and screws are tightened. Tighten the nut until there is no leakage, but it is recommended to go directly to a repair shop for handling. If the car's compressor is working intermittently normally, it is fine because the air conditioner's low-pressure pipe is relatively cold, causing moisture in the air to condense on it.
My old car recently had oil leakage from the low-pressure AC line too, with the aluminum pipe joint completely covered in oil sludge. This is 90% likely due to aging seals, allowing refrigerant oil to leak out along with the refrigerant. I strongly recommend taking it to a professional auto repair shop for inspection—they’ll inject fluorescent dye into the AC system and use a UV light to pinpoint the exact leak. Don’t try to tough it out; running the compressor low on oil will destroy it, and replacing a compressor costs thousands. If caught early, just replacing the seals might suffice, but if the pipe has corroded and developed pinholes, you’ll need to replace the entire low-pressure line.
Don't panic if you find oil leaking from the AC pipe. Last time I dealt with it, the mechanic taught me three emergency measures: immediately turn off the AC switch to prevent the compressor from running idle, use a cleaning agent to thoroughly wipe the leaking area for better observation. The low-pressure pipe is located on the left side of the engine compartment, the one wrapped with insulation cotton that you can feel with your fingers. For minor leaks, you can temporarily tighten the interface screws, but if oil stains reappear within half an hour, don't push your luck. Focus on checking whether the rubber sealing ring is deformed and if there are any dents on the metal pipe body. Remember, after the repair, you must re-evacuate and recharge the refrigerant. Simply topping up the refrigerant at a roadside shop will cause leaks again in a couple of months.
Oil leakage in AC lines is essentially an early warning sign of refrigerant leakage. Although the low-pressure pipe has minimal pressure, persistent seepage can lead to two critical issues: first, the loss of compressor oil resulting in insufficient lubrication, and second, a drastic drop in cooling efficiency. Last week, my car's AC suddenly stopped cooling, and upon inspection, oil stains were found at the low-pressure pipe joint. During repairs, note the following: always select high-pressure-resistant fluororubber seals for replacement, and use dual wrenches when disassembling pipes to prevent thread stripping. Modern vehicles now use aluminum-magnesium alloy pipes that resist corrosion, while older cars with iron pipes require special attention to check for flaking rust-proof coatings.
