A camshaft is a long metal shaft with projections, or “lobes” protruding around it. The job of the camshaft is to open and close the intake and exhaust valves for each engine cylinder in a dedicated sequence.
The lobes of the camshaft are placed at specific locations along the shaft. When the camshaft rotates in unison with the crankshaft (tied together by the timing belt or chain), the lobes push the engine’s intake and exhaust valves open and closed in sequence. This process opens each intake valve to allow air and fuel into a combustion chamber at just the right time to be compressed by the piston. Once combustion is set off by the spark plug, the camshaft opens the exhaust valve to allow the gases created during combustion to escape.
The camshaft must be timed perfectly in relationship with the crankshaft, ensuring that all of the valves - as many as thirty-two - open and close when they should. In doing so, the camshaft allows your engine to run smoothly and to produce the right amount of power under various conditions.
While older engines often had only a single camshaft buried deep in the engine block, most modern engines have anywhere from one to four camshafts mounted at or near the top of the engine.
Since the camshafts of a modern engine are mounted near the top of the engine block in the cylinder head, it is one of the last components to be lubricated with oil when the engine starts up. That is because the oil is housed in the oil pan at the bottom of your engine, and it needs to be pumped to the top by the oil pump. Because this is so, any problems with the flow of oil in the system can cause premature failure of the camshaft and related components.
When a camshaft fails, its lobes tend to wear down. And when that happens, the camshaft is no longer able to actuate the intake and exhaust valves properly. This condition can result in the following:
Camshaft replacement is quite an involved procedure that requires a good deal of tools and training. To replace the camshaft on your vehicle, a technician needs to gain access to the top and front of the engine. This usually requires safely lifting and supporting the vehicle off of the ground, removing shields, guards, covers, ducts, and the serpentine drive belt. The radiator might also need to be removed, depending on the orientation of your engine.
With those items out of the way, a typical camshaft replacement (the procedure differs from one vehicle make and model to the next) involves the following general steps: