Getting to knowyour gauges

With our help, our daughter just purchased her first car. It’s a bit different than our family car in that it uses a variety of gauges, rather than lights, to display key information. Can you explain the importance of these gauges and what they represent? (She understands the tachometer.) — Jack and Susan M.

In addition to the tachometer and speedometer, the three gauges most commonly found in cars measure oil pressure, engine coolant temperature and system voltage.

Oil pressure is vital to engine operation, and if a complete loss of pressure occurs, the car could quickly sustain severe damage. Losing pressure is unlikely unless there’s a loss of oil, which could happen if the kid at the lube shop accidentally double-gaskets the oil filter. More common, though, is a gradual loss of oil due to normal consumption or small, sneaky leaks. By checking the oil level every third or fourth trip to the gas station, one can easily put such concerns to rest.

However, if you notice momentary losses of pressure during sharp turns or while starting or stopping, your engine might be running low on oil. Clicking sounds coming from the top of the engine could be another indicator.

And remember, oil pressure varies between 15-50 pounds per square inch with engine temperature and speed. Higher is better.

Maintaining correct engine temperature is also very important.

An engine that runs too cool will waste fuel, produce greater emissions and wear out more quickly. Excessive temperature, meanwhile, can distort or crack expensive metal parts such as the cylinder heads, pistons and engine block. High temps can also lead to head gasket failure.

With proper cooling system maintenance (checking hoses and belts and getting coolant renewed every four or five years), the odds of a sudden engine failure are slight. But anything’s possible.

Coolant quantity should be checked regularly. Whena vehicle is low on coolant, its engine temperature might remainOKunder easy driving conditions but it’s likely to spike when tested by hill climbing or other challenges. If a sudden loss of coolant occurs, or the thermostat fails to open properly, a driver has perhaps three or four minutes of driving before big trouble will occur.

The ideal engine temperature is about 195-200 degrees under normal driving conditions and perhaps up to 230 degrees when climbing steep, long grades.

System voltage is the least important of the three gauges.

That said, your daughter is far more likely to see low voltage than high voltage.

Low voltage (below 12.6 volts) means the charging system isn’t working. Normal voltage should be about 14 volts, perhaps lower at stops with high accessory use.

High voltage (above 16 volts), while rare, can cause component damage and a sweating, stinky battery.

If the charging system suddenly fails, one has perhaps an hour or two of driving and only a few engine restarts before the battery will become deeply drained. If low voltage and stiff steering suddenly occur together, there’s a good chance the car’s serpentine drive belt has failed. Pull over as soon as possible or severe overheating will quickly set in.

I’d recommend checking gauges at least every five minutes, or, when climbing large hills or mountains, every two minutes or so.