How's Your Engine Literacy?

Image Gallery ILLUSTRATIONS: KEN LIN

Mother's Mechanic

Mary Jacksnon examines some of a mechanic's most frequently asked questions.. By Mary Jackson

Q: What should I do if the alternator light comes on?

A: An activated alternator or battery light means more electricity is being used than is being replaced. The good news is it's probably not fatal—just massively inconvenient. The rule is to keep driving until you reach a service station. Turn off as many electricity-draining accessories as you safely can. The hardest thing the electrical system has to do is start the car, so don't turn the engine off unless it's absolutely necessary.

Warning! If the temperature light comes on at the same time the alternator light is on (or simply by itself), stop the car as soon as you can. The same belt that drives the alternator often drives the water pump. If the water pump stops working, it won't be long before the engine overheats and its internal parts melt. The result will be major damage and expensive repairs.

Q: What is vapor lock?

A: The additives in today's gasoline have raised its volatility, which is the ability to change from a liquid to a vapor. During hot weather, gasoline may actually boil, causing it to stop flowing. The result is vapor lock; the engine is deprived of fuel and lets you know with symptoms such as rough running, loss of power, and in some instances, stalling.

Modern electric fuel pumps located far from the heat of the engine provide more constant pressure to the system and have alleviated the problem in most cars. But if yours isn't one of those, and vapor lock is a problem, try switching from your regular brand of gasoline to another reputable brand. If that doesn't work, it's possible that the fuel lines can be rerouted so they are farther removed from the hot spots of the engine.