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I have a 2013 4matic and it’s making a cyclical sloshing noise behind the dash when the AC is running. I’ve read online that it can be caused by a clogged evap drain, but I’ve seen conflicting reports on where this drain is located.
The car does drip water from around the front skid plate area, but I’ve also seen other models with the drain line running through the firewall and behind the radio area.
anyone have a definitive location for where to clean this out (or any other causal suggestions)?
I had this problem develop last year and it was intermittent (hard to duplicate). Took it to two different repair shops and they couldn't replicate the noise.
I was living with the noise since it only appeared maybe twice a month. February 2026 I finally had the time to replace my aircon compressor 000-830-26-00 and it appears to resolved the noise issue. Current milage is 140,000 miles (225,300 kilometers). I had another shop discharge the refrigerant, I spent about 30 minutes removing the compressor myself, and finally went back to the shop to recharge properly.
2010 GLK350, 2021 Taco, 2019 Lexus GX460, 2009 BMW 335d, BMW 328xi
Recharging the system may fix it. I’ve had a similar issue, sloshing or slurping kind of sound in a couple of cars, and charging the ac system has eliminated it. Autozone and other car parts stores sell cans of refrigerant that are very easy to use.
Locate the hose that’s dripping when ac is running , it’s right under the middle area of the motor . Run a thin piece of metal up it carefully, see if any extra water pours out . Does AC stink ? They sell cans of a spray that actualy kill mold , but don’t drive it for like 30 minutes after , ledge ac on , motor running , and windows open to get the chemicals out. Hopefully it’s some mold blocking the hose. The oil dipstick might go up the AC condensate hose . YouTube surely has a lot of videos on clogged ac condensate hoses and cleaning mold . Any auto store has AC coil cleaner
Don’t just autozone a can of Freon , you can ruin a system and Compressor overfilling it. A pro is best as a set of gauges is needed and the correct type of refrigerant. The in a can stuff might do more harm from interactions . A lot of crap additives harm . On a 3000 junk ok. A pro might be best at this point.
Look for the hose hanging down that drips, when ac is on, that’s the condensate line to clear.
Locate the hose that’s dripping when ac is running , it’s right under the middle area of the motor . Run a thin piece of metal up it carefully, see if any extra water pours out . Does AC stink ? They sell cans of a spray that actualy kill mold , but don’t drive it for like 30 minutes after , ledge ac on , motor running , and windows open to get the chemicals out. Hopefully it’s some mold blocking the hose. The oil dipstick might go up the AC condensate hose . YouTube surely has a lot of videos on clogged ac condensate hoses and cleaning mold . Any auto store has AC coil cleaner
thanks for the reply. I think this is going to be my first order of business. The AC doesn’t smell at all, it’s just the sloshing for now, but if this doesn’t resolve it another poster above recommended changing the condenser, which I might do if cleaning the drain doesn’t work.
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