If a car is "drinking" coolant by the gallon, the news is probably going to be bad.
Dear Tom and Ray:
I have a 1994 Volvo Wagon that is drinking all of its coolant. I can't drive more than a few miles before all the coolant is gone. Then the heater gives out and the car overheats. I haven't noticed any leaks anywhere from the engine. I think it is all coming out of the exhaust. What is the problem? -- Keith
RAY: Are you sitting down, Keith?
TOM: You might want to just close the newspaper right now. You know, just turn the page, and pretend you never saw your letter in the paper.
RAY: Well, if you're still reading, the coolant is definitely coming out of the exhaust. That means the church-and-state-style separation that is supposed to be enforced between combustion chamber and coolant has been breached in your engine. And it sounds like it ain't a minor breach.
TOM: You're probably not losing ALL of your coolant every few miles; if you were, your engine would seize. But you might be losing all of the coolant in the overflow container. And even that's enough for us to conclude that your problem is serious.
RAY: If it's just a blown head gasket, you should expect to pay somewhere in the $1,500 range to get it fixed.
TOM: If it's worse than that, and you've cracked the head or the block, then you're into home-equity-loan territory.
RAY: So, screw up your courage and ask your mechanic to find out what's going on. He won't know for certain until he takes the head off and gets a look inside. While you don't need to take the plates off before you drop it off at the shop, you might want to check the screws that hold the plates on and make sure they're moving freely. Good luck, Keith.