Weird Coolant "Leak"

[sketchman]

Owner says it is losing coolant slowly. It never overheats, but has a strong smell of coolant inside the car. However there is also no wet carpet or dripping out the drain tube in the firewall.

My theory - a hairline crack in the heater core only leaks when it gets hot enough to expand. It is so tiny a leak that it vaporizes and so the smell is strong but it never gets damp.

Owner wants the head gaskets changed anyway, even though we pressurized the coolant system up to 20psi and it never lost a drop of coolant.

I'll gladly take the money to do the job, but I just can't see a leaky head gasket not leaking under pressure. The owner even said he parked it and let it run with cardboard under the engine, and it never leaked.

Anyone ever experienced this? Theories?

[gergorian]

That is an odd situation, but I agree with you. I think it is most likely a hairline crack in the heater core. It is the most likely culprit with all the diagnosis you and the owner have done.

[Pu241]

If he can go without heat this time of year,re-route the coolant so that it by passes the heater core, and see if the coolant loss and odor go away.

[kumalaba]

^ what john says sketch then you dont have the hassle of pulling the hc. i have you a nc if you need one. danny

[sketchman]

Ah, that's a good idea about looping the lines.

I already did the head gaskets, and the smell is still there. So that'll be next. At this point, though, the heater core is the only thing left.

Oh, and thanks kum, but it's not a Festiva. GM product. 3.4 V6.

[kumalaba]

oh ok goodluck with it

[Movin]

Probably a pile of dried crusty right where you think it is!

[lessersivad]

GM heater cores are usually plastic tanks and tubes from the factory. It isn't uncommon for them to develop a small crack in one of the tubes.

I fumbled around with a 2003 Grand Am for a month trying to figure where the coolant was going. Sloooow leak with no drips on the ground. Pretty much same deal except no coolant smell. Removing the hoses at the heater core revealed metal tubes coming from the core.

Multiple 'damp leaks' at a few hose fittings. Replaced all of the squeeze type clamps with standard hose clamps FINALLY fixed the problem.

Hope this helps.

[sketchman]

^Good stuff. I'll grab a bag of them to try too.