The camshaft’s function is to open and close the valves at the top of each cylinder within the engine. Each cylinder has at least two valves – one that draws in a combustible air and fuel mixture that, when ignited, forces the piston downwards in the cylinder. As the piston moves back up in the cylinder, the other valve opens to release the exhaust gases left from that combustion.
The camshaft itself is a metal rail, made of iron or steel, that sits above the cylinders at the top of the engine. The shaft is marked by egg-shaped projections, known as cam lobes, that are spaced at intervals along its length and which align with the valves. As the camshaft rotates, the peaked end of each lobe makes contact with a lever, called a ‘rocker arm’, which opens the valve to the engine. As the lobe’s peak moves past the rocker arm, the lever moves back to its original position and the valve closes.
Pretty simple really.
Except, as with most things, it really isn’t. The physical mechanics might be simple enough, but the interaction of the camshaft with other components is critical to the engine’s performance and must be expertly maintained.
The camshaft’s movement is synchronised very specifically to the movement of the crankshaft – the component at the base of the engine that rotates thanks to the vertical movement of the pistons. In most engines, open valves and pistons occupy the same space within the cylinder at different times, so it is vital that the timing of their movement be exact. If the two were to come into contact, then severe, perhaps irreparable, damage can be done.
WHAT CAN GO WRONG?
As with any moving component, things can go awry. The lobes on the camshaft can wear over time and if the system around the camshaft is not maintained well – if oil leaks from the system, or dirt and debris gets inside – then damage can occur. Problems can manifest as popping noises from the tailpipe or a ticking noise from the camshaft location,
Another problem may come from the camshaft sensor. It is an electronic device used by a vehicle’s engine management system to monitor the position of the camshaft as it relates to the crankshaft. The system uses this data to assist in the control of the fuel injection and ignition system. Should the camshaft sensor be faulty, the vehicle can experience ignition problems; a loss of, or surge, in power; engine stall; and impaired performance and fuel economy.
The most ruinous damage is done when the timing between the movement of the crankshaft and camshaft is off. When this happens – and the timing belt is usually the culprit here – then the pistons and valves can crunch together inside the cylinder and the domino effect can include not only damaged valves, but damaged lobes, bent or broken rocker arms, and even a bent, cracked or broken camshaft. Should this happen, the engine could potentially be a write off.
WHAT CAN BE DONE WITH A DAMAGED CAMSHAFT?
If the camshaft itself is damaged, it may turn out to be just as cost effective to replace it as it is to repair, if indeed a repair is possible. However, replacing a camshaft is still a labour-intensive job and can take an experienced mechanic several hours to complete. Along with the price of a new camshaft, a cost somewhere in the region of $1500 can be expected on most standard cars.
As with all things, prevention is better than cure, and recognising that something is amiss with your vehicle, and getting any issues diagnosed and fixed before they become something more serious, is always the best option.
9 January 2020
Please note the information contained on this page is general in nature and does not take into account your specific needs or circumstances. You should consider whether the information is appropriate to your needs, and where appropriate, seek professional advice.