coolant smell is never a good sign, right?

[RITmusic2k]

Hey all,

I'm thinking I have a heater core coolant leak, but just wanted to run this by everyone just in case this specific failure mode means something different:

I usually avoid using air conditioning; I drive with the fan blowing and A/C off, and all is normal. But when it's just too hot to avoid it, I'll turn on the A/C and again everything is A-OK, until after I switch A/C back off and then I get a huge amount of coolant vapor coming out the vents. We're talking not just enough to smell it strongly, but enough to feel the humidity of it. This persists for as long as it takes to blow it all out and things start smelling/feeling normal again, until the next time I turn A/C on then off.

So, how bad are we talking here - new heater core, or something else? Is it at all DIYable?

[BavarianZHP]

I'm interested in this as well. Right after I shut down the A/C there's this very strong moldy smell that follows - never happens during or without A/C, only right after I shut it off. It's pretty nasty...

[brettbimmer]

Are you sure that this isn't just condensation inside the duct work when you turn off the A/C compressor? It sometimes looks bad depending on the amount of humidity in the air -almost like a white mist in your face. I'm going with this is normal vehicle operation when cycling the compressor on and off rather infrequently.

Nonetheless, are you losing any coolant? Does the air coming out of the vents smell significantly like coolant?

[BavarianZHP]

That may be my issue! I'll need to look into that. However, I think the OP is smelling coolant. It's hard to mistake that coolant smell for anything else.

[WOLFN8TR]

Are you sure that this isn't just condensation inside the duct work when you turn off the A/C compressor? It sometimes looks bad depending on the amount of humidity in the air -almost like a white mist in your face. I'm going with this is normal vehicle operation when cycling the compressor on and off rather infrequently.

Nonetheless, are you losing any coolant? Does the air coming out of the vents smell significantly like coolant?

X2...That was my thought also.

[RITmusic2k]

It's definitely a coolant smell. And enough at that to almost make breathing uncomfortable for those first few minutes after turning off the A/C.

I can't say for sure whether I'm losing coolant badly, as this is a newly-noticed issue. At present my coolant level is below max, but definitely above the minimum... I'll start tracking it over time to see if I can measure it going down.

I don't know if there's any other test I need to perform (i.e., try driving for a week or so with the A/C system running at all times), as this is still a flaw in the system... but I want to do something about it right away.

[brettbimmer]

Hmmm...what about turning on the heater with the car up to temperature and seeing if you have the same coolant smell? Also, could it be that another coolant fitting under the hood is leaking a bit, and the smell is coming through the vents? (check back in those difficult-to-spot areas near the firewall).

Having thought about this for the afternoon, what is most odd is that if you had a leak in the cooling system anywhere, my best guess is that you should smell it anytime the HVAC fan is running, not only when the A/C compressor has been disengaged. The A/C compressor system is completely separate from the engine coolant/heater loop, unless I am mistaken.

[BavarianZHP]

I'm not sure about the health impacts of breathing coolant, but it cannot be good. That stuff is poisonous.

[RITmusic2k]

Having thought about this for the afternoon, what is most odd is that if you had a leak in the cooling system anywhere, my best guess is that you should smell it anytime the HVAC fan is running, not only when the A/C compressor has been disengaged.

That's my thought/confusion as well.

So, ever since yesterday I've been driving with the system running on full auto (e.g., A/C on, never turning it off for the last minutes of the drive, etc.). I do not have the coolant smell, though I have actually started to smell the slightly musty smell of old moisture in the system, crossed with something like the distinctive 'crayola' scent of the car's insulation/glue...

My condenser seems to be working overtime, though. It might just be because of the current heatwave here, but when I parked my car I left a very steady stream of water droplets as I moved. Oh well. I'm gonna keep running the car this way for the rest of the week, then see what happens when I switch the A/C back off again.

[wsmeyer]

I'm pretty sure it's your heater core. Here's my guess.

When you turn the AC on the runners are redirected through the AC system. The fumes would then be accumulating in the now closed off heater area. When you turn off the AC the runners are diverted back through the heater system and the built up fumes are released.

[Hermes]

heater core replacement is not fun... hopefully it's just some of the plumbing

[RITmusic2k]

Thanks for the info, Will! I guess it's time to start investigating the replacement process...