The Ford Focus, a compact car, was introduced in 1999. If you own an older model Focus that is approaching 100,000 miles, there are several potential problems to look out for. Each of these issues is detailed in the maintenance section of the Focus owner's manual.
The Ford Focus owner's manual suggests that owners change the vehicle's engine coolant after 105,000 miles. A vehicle in need of engine coolant may experience fan failure and overheating. Consider using "extended service" antifreeze when changing the coolant, because it lasts an estimated 150,000 miles.
The Focus owner's manual also states that the spark plugs must be replaced around the 100,000 mile mark. Old spark plugs can damage your engine and cause misfiring, especially in cold weather. New spark plugs will improve the engine's overall performance and your vehicle's emissions. Failing to replace your spark plugs increases the risk of catalytic converter failure.
The owner's manual suggests checking the belts at 105,000 miles. The serpentine belt is usually the first to fail at around 100,000 miles. A faulty serpentine belt is indicated by a "squealing" noise and may increase transmission slippage. The timing belt should also be examined when replacing a serpentine belt.