If you have more than a few years of driving experience, you’re probably familiar with the indicators of potentially catastrophic car repairs. You know to stop and pull off to the side of the road if a flashing (as opposed to a steady) Check Engine light appears, if the oil-pressure warning light comes on, if the coolant-temperature gauge heads into the red zone, if the brake pedal suddenly goes “soft” when you apply it, or if a tire goes flat. Keep driving and you risk demolishing your car’s engine or—in the case of tires or brakes—jeopardizing your safety. But some potential automotive disasters give either a subtle warning or none at all. Watch for these:
1. Underinflated tires
Tires low on air pose a safety risk, waste fuel, and can self-destruct. A tire-pressure monitoring system (TPMS) has been standard on cars since model year 2008; a dash warning light indicates loss of pressure in one or more tires (some systems even indicate which tire is low). Yet according to a survey by Schrader International, a maker of TPMS components, 42 percent of drivers fail to identify the light when it comes on.
Cost to properly inflate tires: $10–20 for a basic tire-pressure gauge. (Gauges attached to the air hoses at gas stations are notoriously unreliable.)
Cost to replace a set of tires: $500 or more. Incidentally, the TPMS light comes on only after a tire is 25 percent or more underinflated, which is dangerously low. Check the pressure at least once a month. If your car still has its original tires, the correct pressure can be found in the owner’s manual or on the driver’s doorjamb. Otherwise, you should check with the tire manufacturer or a trusted professional directly to get an inflation recommendation—and that figure can vary depending on the ways in which you use your vehicle. Don’t inflate the tire to the pressure stamped on the tire sidewall; that’s the maximum sustainable pressure. Doing so may negatively affect your vehicle’s handling and the life of the tire.
2. Skipped fluid changes
At one or more points in a car’s life, automakers may require that the cooling system be flushed and the brake and transmission fluids be replaced. Scheduled changes vary considerably among car manufacturers, so check your owner’s manual. You can also have a repair shop you trust test a fluid to see if it’s contaminated or has lost its strength and is ready for a change. Neglecting a needed fluid change can cause significant damage to system components.
Cost to change the transmission fluid: $200 or more.
Cost to replace a transmission: $4,000 to $9,000.
3. Failed oxygen sensor
Several conditions can trigger the steady glow of a “Check Engine” light. High on the list is a defective oxygen sensor. The little gizmo’s job is to monitor the oxygen level of the exhaust so that the engine’s computer can adjust fuel levels for maximum efficiency. When it fails, the engine may not get enough fuel or it may run “rich,” gulping down fuel—which will cost you money. Your wallet will take an even bigger hit if excess fuel destroys the car’s catalytic converter.
Cost to replace a sensor: $250 or more.
Cost to replace a catalytic converter: as much as $2,000 to $4,000.
4. Worn brake pads
Disc brakes tend to squeal when you apply them—annoying but often harmless (still, have it checked out). But if the brakes squeal when you’re not depressing the pedal or if you hear grinding noises when you depress it, the problem could be serious. Have your car looked at right away—very likely, it’s time for new brake pads. Ignore the noise and metal-to-metal contact in the brake system and it will result in deeply scored rotors that must be replaced.
Cost to change pads: as little as $250 per axle.
Cost to replace rotors: an additional $100 to $200 for each rotor (one per wheel); for performance brakes (increasingly common these days), rotors can cost nearly $1,000 each.
5. Aged timing belt
The timing belt operates the camshaft, which opens and closes the engine valves. It’s inside the engine and can’t easily be inspected. Some engines use a timing chain instead, which doesn’t need regular replacement. But if a timing belt breaks, valves may collide with pistons, essentially destroying the engine. So you’re flirting with disaster if you fail to replace your car’s timing belt according to your owner’s manual’s recommendations. You should replace several related items at the same time while the engine is partially disassembled, including the water pump, tensioners, idlers, and various seals.
Cost to change a timing belt: $750 to $1,200.
Cost of a new engine: $4,000 and up—way up, in some cases.
You can ignore any of these factors and motor on, perhaps for many miles. But you do so at your peril—eventually they’ll get you in the wallet, big-time. It’s best to simply heed the old adage: Don’t be penny-wise and pound foolish.
Peter Bohr has been writing about cars for more than four decades.