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Smell on Hills

Hello. I have a 2008 Honda Odyssey. Lately, we’ve been bothered by a sweet smell, particularly when coming to a stop at the bottom of a hill or acceleration uphill. The smell is most noticeable from the two front, center AC vents. The dealer swears it’s not a hose or heater core issue. He also checked the cabin air filter. AC “on” and recirc “on” seem to exacerbate the problem. Any ideas?

A sweet smell from the ventilation system usually points to a leaking heater core. And if the vent system is set on recirc, the escaping coolant concentrates in the passenger cabin and the sweet smell gets stronger.

Take it back to the dealer and have them find the sweet smell at your satisfaction. Because if it’s coolant leaking into the passenger cabin, you don’t want to breathe that in over time.


It almost certainly has to be a coolant leak. I’d get a 2nd opinion and have them put a pressure test on the system to see if there’s a drop over time. Is your coolant jug below recommended levels? Is there a film on the inside of the windshield? If those are eliminated then it’s something else. Possibly a clogged AC drain but the oder isn’t usually considered sweet.

Thanks to both of you for confirming my suspicions. I will call the dealer first thing.