Dear Jim,

I bought a new battery for my 1986 Lincoln Mark VII (5.0 L, V8) about four months ago, and it's already going dead. If I'm not running the air conditioner, it's OK, but if I run it, the battery dies and the car needs to be jumpstarted. Someone told me this is a charging problem, not a battery problem. Is that right?

--Corey Haight

You bet, bro. These are the symptoms of a bad alternator, and it's a common problem this time of year. The AC in your car needs a lot of power to run, and it's sucking it away from the battery faster than it can be put back by the weak alternator you have in there. Have the unit replaced, then check the power at the battery with the engine running. It should be anywhere from 13.2 to 14.5 volts. If it's not in that range, even with the new alternator, then you might need to replace something called the external voltage regulator as well before your battery stops getting drained dry.

Tip of the Week:

Your car has overheated in heavy traffic and the mechanic says you have one of those ugly-sounding problems that sends cars to the junkyard: a blown head gasket, cracked head or cracked engine block. That's a colossally expensive repair -- or is it? Before doing anything else, try something called K&W permanent metallic block sealer. The stuff comes in a 16-ounce can, costs less than $10 and potentially could save you thousands in major engine work.

Make sure you follow the label instructions exactly, but here's the basic deal: Drain your radiator completely, flush it out and fill it again with water. This step is to get rid of all antifreeze in the system, because block sealer won't work with antifreeze lingering around. Remove the radiator cap (NOT when the engine is hot), shake the can hard, pour in the sealer, replace the cap and then let the car idle for 20 to 30 minutes. Stop the car, remove the radiator cap and don't do anything at all with it for 24 hours. This will give the sealer time to dry into those cracks and form a super-solid bond.

Finally, drain the radiator again and fill it with a fresh water/antifreeze mix. If you've done everything right, that new seal should last longer than just about everything else on the car.

Buffalo Jim, owner of Allstate Auto & Marine Repair in Las Vegas, 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.