smoke/fog coming out of the air vent
 

Hey guys, lately I notice that once in awhile, and usually it either happen in the early morning or late at night, there are smoke or steam like coming out of my air vents. If I turn on the air or AC, the smoke went away. I searched around, some said it could be just hot and cold air mixed together, causing this steam to come out. There are some said my heater core could be leaking. My coolant does go low, but that happened the past 3 years, and the rate is very slow. Is there a location where I can check if I do have a leak inside the car? It is a 95 Honda Accord.

Thanks.

Re: smoke/fog coming out of the air vent
 

If the heater core is leaking and the drain is no longer working the carpet may become wet.

Turn the defrost on(AC off) if the condensation on the windows gets worse then it most likely is the heater core. Would also smell 'sweet' from the antifreeze.

Re: smoke/fog coming out of the air vent
 

The car smell bad lately when I turn off the recycle air, but it not a sweet smell. I will test out what you mentioned and see if thats it. Thanks

Re: smoke/fog coming out of the air vent
 

So I drove home today, no steam coming out of the vents, although the smell is there. It could be smell like antifreeze burning, but a lot stronger I guess. After I shut off the car, left for less than 5 minutes, I saw some fog build up in the windshield. I did what Mike said, no worse or better. I checked both driver side and passenger side carpet, and looked under the dashboard, no sign of any leaks.

What other location I need to check? Anything else to test?

Re: smoke/fog coming out of the air vent
 

Sounds like textbook heater core leakage. I just replaced mine and my coolant loss was very small but noticeable every other day or so about an inch lost from reservoir

Re: smoke/fog coming out of the air vent
 

Is it hard to replace? Do I have to take out the dashboard? Or am I safe to leave it alone and keep an eye on the antifreeze fluid?

Just searched around more, look like I might go the bypass the heater core route. Would that be safe for a long time or is that just a temporary thing?