Today's cars have complex systems with many components, many of which can cause a clicking, tapping or rattling noise when they start to fail. Drivers experiencing this unusual sound may have to let a mechanic examine the ignition, climate control, electrical, exhaust or other systems to track down the cause of the problem. Some clicking noises signal a simple replacement part, while others may warn of imminent engine failure.
When a car engine makes a clicking noise, it may not have sufficient clean oil to lubricate itself properly, according to 2 Car Pros. Dirty or low oil can cause the engine's valve lifter to malfunction, leading to clicking sounds in the engine. If the car goes too long without having its oil and filter changed, the engine bearings could eventually fail, causing not only further noise but also permanent damage to the engine.
Ignition and Exhaust
The ignition system in a car can produce a clicking noise if it has lost its efficiency. If any component of this system fails or mistimes, the system may discharge electricity to ground. This discharge can manifest itself as a clicking sound. The spark plugs can also produce clicking noises on their own if they become loose.
Heating and Air Conditioning
A car's climate control systems include components that can produce a clicking noise if they fail or require service. One of these components, the heater plenum, contains devices called blend doors that control the mix of cool air to warm air as the user switches the controls from one climate setting to another. These blend doors run on an electric actuator that can produce clicking noises when it fails. The air conditioner compressor may also make a soft clicking noise if its refrigerant supply has run low.
Belts, Joints and Supports
Many of the support systems on a car can cause a clicking noise if they malfunction or wear out. Struts and shock absorbers include hydraulic dampening valves that will click or rattle if they lose their internal oil pressure. Worn CV (constant velocity) joints on the front axle can also make clicking or popping noises, according to AA1Car. Damaged CV joints make a pronounced clicking noise when accelerating or making sharp turns. Additionally, a loose serpentine belt can cause a clicking sound. Replacing the belt's tensioner can alleviate the problem.
Low voltage from the car's battery can lead to rapid clicking or ticking noises when the driver tries to start the car. As a battery ages it may lose its ability to deliver a consistent 12 volts of electricity to the starter. In this case, when the driver turns the ignition key, the starter turns itself on and off rapidly, resulting in a rapid succession of clicking sounds. The driver may have to replace either the battery or the alternator that supplies electrical charges to the battery.