How a Timing Belt Works

Introduction:

A timing belt is used to drive the engine's camshaft. The engine crankshaft utilizes a drive sprocket to connect with a larger camshaft sprocket via a timing belt. A typical timing belt is constructed of a fiber enforced rubber belt with horizontal ribs molded to the inside of the belt. Tension is held on the belt by a belt tensioner which is spring loaded, oil pressure activated or set manually. Timing belts can be used to drive accessories such as a water pump or power steering pump. Some engines utilize a timing belt to drive balance shafts inside the engine that help neutralize engine vibration. When a timing belt fails it will allow the horizontal ribs to shred allowing the driven shaft to stop or become misaligned resulting in engine operation failure. Each engine has a unique set of timing crankshaft, camshaft and accessory marks that can be located: timing belt marks or in a car repair manual.

To check the condition of the timing belt (engine off) remove the top dust/safety cover from the upper section of the engine front by removing a few bolts you can access the timing belt. Next, using a flash light inspect the condition of the belt, check for cracks, especially at the base of drive teeth. If the timing belt shows signs of wear or if you are replacing it for maintenance purposes complete exposure of the belt and related components are necessary. For step by step instructions for your particular car engine you must consult a car repair manual.

Basic Replacement Procedure:

Remove all obstructions from engine front, if an engine mount is in the way, support the engine from the top or bottom whichever is more convenient

Remove upper and lower timing belt covers to gain access

Remove or loosen timing belt tensioner to release the timing belt

Remove timing belt and clean all debris from area

Use a timing belt diagram to time the crankshaft to the camshaft - Timing belt diagrams

Replace timing belt with tensioner (if needed)

Re-install timing belt and reassemble as needed

Note: If the timing belt drives the water pump it is a good idea to replace it at this time to avoid failure. Occasionally when bearing tension is released and then reloaded it can have an adverse effect on internal bearings.