Smoke in the heater vents and the smell of coolant? Sounds like a leaky heater core.

Dear Car Talk

Dear Car Talk | Dec 01, 1996

Dear Tom and Ray:

I own a 1979 Chrysler LeBaron. When I first start the car "smoke" comes out
of the heater vents. This doesn't happen every time, but when it does
there's also a strange odor. Do you have any idea what this might be? --
Brenda

RAY: Sure. It sounds like a leaky heater core, Brenda.

TOM: It's not smoke. It's actually coolant vapor. And that slightly sweet
odor is the coolant that's leaking out.

RAY: There's a little radiator under your dashboard called a heater core.
Hot coolant from the engine flows through there and transfers heat to the
vents which carry the heat to the passenger compartment.

TOM: And it's supposed to be a closed system. That is, all the coolant that
flows into the heater core is supposed to flow back out of the heater core
and back to the engine. But yours obviously isn't playing by the rules, and
it's leaking a small amount of coolant into your vents.

RAY: It's probably a small leak right now. But if you don't fix it, you'll
eventually have low coolant level, your engine will overheat and possibly
get ruined.

TOM: So if you've been dying to get rid of this LeBaron, I'd just leave it
alone and keep driving, and sooner or later you'll run out of coolant and
the engine will melt. But if you want to hang on to it for a few more
years, I'd spend a few hundred bucks now and get the heater core replaced.
Good luck, Brenda.

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