Unexplained powder leak under car
Powdery residue or thick wet powder under the car often originates from a leaking air conditioning drain tube after heavy use. This residue leaves motorists confused about whether it signals a severe mechanical failure or simply a localized AC system issue.
What the numbers show
Counted from the threads quoted below. How we count
- This comes up 9.7× more often in r/MechanicAdvice than across the site as a whole.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
Found another way around this?
Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.
- 1Checking coolant levelsDid this help you?
- 2Inspecting for puddles on the ground while parkedDid this help you?
- 3Taking the vehicle to local shops for diagnosticsDid this help you?
- 4Continuously recharging the air conditioning systemDid this help you?
- 5Asking online mechanics to identify the fluid based on descriptions or photosDid this help you?
- 6Asking online forums to identify fluid colorsDid this help you?
- 7Tasting the fluid to check for sweetnessDid this help you?
- 8Checking if the fluid glowsDid this help you?
- 9Dipping a finger in the fluid to smell or taste it to identify what it might be.Did this help you?
- 10searching above the drip area to trace the fluid pathDid this help you?
- 11asking online forums to identify unknown parts and leak sourcesDid this help you?
- 12Touching and testing the fluid to determine its identityDid this help you?
In their words
Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.
“This morning I noticed a wet spot underneath. Any thoughts?”source ↗
“I notice this strange green liquid on the driveway and im assuming this has to do something with Mechanic and since I have no knowledge over that type of stuff, I’m asking you guys to see if any of you are able to identify this”source ↗
“Was doing oil change in car and saw on passenger side of car this wet looking spill. When touched it was powder really thick powder I removed the cover but saw nowhere where this could come from??”source ↗
“It’s powdered though? Never seen a previous car do that maybe I’m missing something.”source ↗
“The open tube in focus is leaking something. My vehicle has been having AC issues through this hot summer and I've had to recharge it multiple times.”source ↗
“The leaking fluid has made a puddle with a rainbow oily look.”source ↗
“I have a 2009 2.7 l Tacoma leaking oil. Wondering what this part is where it appears to be leaking oil.”source ↗
“Yesterday I noticed this puddle under my Seat Mii Eco 2014. It was an hour after a 45 minute drive with a turned on A/C. Is it from the A/C or can it be from the breaks? Or something else?”source ↗
Where this came up
People with this problem also raised
- 8Metal scraping noise and fluid leak under car
- 17How to tell if a coolant leak is a water pump failure
- 2Is a drip from my exhaust normal or a leak?
- 11Is a clear fluid leak from my car or heat pump dangerous?
- 16Mystery part fell out during car repair — what is it?
- 12Is my outside unit leaking oil or condensation?