I have a 1993 4runner (v6, manual) that is losing about a quart of coolant every 500 miles. I haven't been able to find a leak. There are never any wet spots on the engine or any puddles under the car. The engine runs fine with no smoke so I don't think it is a bad head gasket. The underside of the dash and the carpet are dry so I don't see evidence of a heater core leak. Any ideas where the coolant may be going?

*Could be as simple as a pinhole shooting coolant onto a hot manifold when system is under pressure...or the more common destination of missing coolant. Which unfortunately is coolant heaven after its burned in the combustion chamber. If there are no obvious signs of external leakage, and the interior is nice and dry, might try pulling your spark plugs and look for one or more that are "clean" compared to the rest. Head Gasket failure is rarely a quick catastrophic (wow big word for me...) failure. Starts off un-noticed, then the sure signs appear like rough idle or missing coolant. As it progresses it becomes more obvious then it fails and you get the white plume out the tailpipe. Best to check it out sooner than later. Hopefully more of the V6 lovers will chime in....
~Darin <img src="/forums/images/graemlins/baby.gif" alt="" />

Hate to say it, but polish up the torque wrenchs cause I see a head gaskit job in your future. Try letting the truck set for a day, then remove all the spark plugs one by one and compare them. If you find ANY signs of rust forming on the the tip of a plug it's a sure bet moisture is entering that cylinder. Like I say, I sure hope I'm wrong, but I've been in many of these v-6's for this reason and they all started out with the same symptoms.

I agree with John and Darin. That's usually the sign of an impending head gasket repair.

But, before you conclude that it's all doom and gloom, get a cooling system pressure check and be sure it's not something harmless and less drastic to repair like a weeping hose.

Mine started ouy just like that.I was hoping to make it through the winter but I will be pulling the heads this weekend.I hope it's not the headgaskets so goodluck.Run you VIN for the V06 at the dealer and do the knock sensor wire.