Dear Jim,

My 1993 Ford Explorer (4.0L, V6) has developed a coolant leak somewhere. After it's been parked for a while, I usually find quite a bit of green liquid pooled in the driveway.

My son opened the hood but couldn't find anything wrong with the radiator. It actually looks like coolant is leaking from somewhere behind the engine and not from the engine itself. Do you know what's causing this?

Does it matter that I use the environmentally safe kind of antifreeze? Is getting this fixed going to cost me all the money I've been saving for vacation?

-- Deborah Sparks

I'll answer that last question first, sister, because you're obviously excited about this trip: No, I doubt very much that the repair bill is going to cut seriously into your vacation funds.

The fact that coolant seems to be leaking from somewhere behind the engine is important here, and I'll explain why. Your Ford has something underneath the dashboard called a heater core, and it uses coolant from the radiator to heat your car interior on these chilly nights.

Most likely, the green puddles you're seeing are due to a leaky hose running between the radiator and the heater core.

It's also possible you have a bad heater control valve -- the part that actually regulates flow of coolant to the heater core. Whichever of these is the case, it's an easy fix that any qualified mechanic can complete in less than half an hour.

In a worst-case scenario, you have a bad freeze plug or two in the back of the engine. Freeze plugs are designed to pop out if the water ever freezes in your cooling system, giving the ice room to expand and saving your engine block from serious damage. The thing is, they're usually made of tin, and tin rusts pretty easily.

Even if that's the problem, the whole repair shouldn't cost more than $200, maximum. If it's just a bad valve ($50) or a hose ($20), then your vacation will be that much nicer.

As for the environmentally safe antifreeze, sister, that's not a factor here. The stuff functions just the same as traditional antifreeze, except that it's far less poisonous to kids and pets -- definitely a good thing when it's pooling in your driveway.

Tip of the Week

If you ever do need those freeze plugs replaced, drivers, make sure they're made of brass, not tin. You'll pay a little more for the brass variety, but high resistance to rust and corrosion makes them worth it.

Buffalo Jim, owner of Allstate Auto & Marine Repair, writes a weekly column. Send your automotive questions to him at buffalojim@lasvegasniftynickel.com. If Jim picks your question to answer in Nuts & Bolts, you'll also be the proud recipient of a deck of official Buffalo Jim playing cards, presented in a classy, tin box bearing his hairy image.