For the last two months, whenever I fill up the radiator and the reserve bottle, the next day the reserve bottle is completely empty and the radiator is low maybe a quarter of a cup. It doesn't make sense to me because if I let it go for weeks it will not go down anymore than that quarter of a cup. I think it might be the cap but I have no idea, also the rubber tubing between the two is in good condition as far as I can tell. Thanks in advance!

 

I have the same problem, mysteriously vanishing coolant. I have the noticeable gush through the heater core, and I'll top off the coolant and it gradually disappears again. No leaks on the garage floor or in the driveway. Occaisonally I'll get a wiff of the sweet smell of coolant after a long drive. But I can not detect a leak anywhere. Can't be a head or intake gasket, because there is no evidence of coolant in the oil. I am completely baffled. HELP!!

 

Ya it doesn't make any sense, and my truck has never over heated or been above 210 in hot south Florida heat

 

Check for a few things.

1. On the passenger side right under the dash is the floor damp?
2. Turn the heat on for about 5 min, does your windows get foggy or do you feel a greasy film on the passenger side window.
3. Turn the truck on let run for 5 min. Then turn heat on using the vents that face you. Do you see a little bit of smoke.

If you said yes to any of these, then your heator core toast. I have the same issue, no ground spots, but coolant is missing.

 

Well my heater doesnt work at all (winter gets around 60) so that could be the culprit. Wouldn't I have to use my heater to have it leak? Thanks for the advice I'll check this when I leave work

 

Not really. I haven't used mine since February and I'm missing coolant.

 

So just out of curiosity, what does the heater core use the coolant for? To heat the truck with the heat off the engine?

 

Quoted from wiki.

"Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins attached to the core tubes serve to increase surface for heat transfer to air that is forced past them, by a fan, thereby heating the passenger compartment."

 

Wow I'm impressed they actually use common sense. I thought this gas guzzler just used more gas somewhere to warm up the cab lol

 

The older air cooled volkswagens had an optional gas heater.... it was NICE. INSTANT heat. Trouble was, if your gas got stale, the heater would smell funny......