How are Camshaft issues diagnosed?
Since the camshaft can fail by seizing or by flattening out a lobe, the technician will either receive a vehicle that runs terribly and misses on one or more cylinders repeatedly. If the engine will not crank or start, the technician will notice that the starter engaged with good battery voltage, but could not turn the engine. The engine will be turned by hand, and the technician will find they can not turn the engine. At this point, the engine is declared seized, but removal of the timing chain or belt must be done to verify if the camshaft or crankshaft has seized. If the engine cranks, but cranks quickly and without pulsation, the timing belt or chain will be inspected. If mission, the camshaft will be turned by hand, but will likely be seized. Finally, if the vehicle runs rough, the technician will begin by reading on-board diagnostic trouble codes, will find misfires on likely one cylinder, and will begin diagnostics by testing several other components. The ignition coil, spark plug, fuel injector and fuel injector seals will be tested. Afterwards, engine vacuum leak testing may even be conducted before the camshaft is suspected of failure. Once these items have been ruled out, the camshaft valve cover will be removed, and the camshaft will be directly inspected, or the lift of the rocker arms will be checked with a dial indicator. Once tested, it will be obvious that the camshaft lobe is no longer lifting the cylinder head valve enough to allow for proper operation.
How are Camshafts replaced?
For engines with the camshaft mounted internally in the engine block, either the engine will require removal, partial removal, or many components will be removed to gain adequate clearance to slide the camshaft out of the front of the engine, check the status of the camshaft bearings, and instal new components. Engines with overhead cams will require removal of the timing covers, timing adjusters, timing belt or chain, valve covers, camshaft bearing caps or girdle, and any other obstructing components. Then camshaft can be lifted out, and the bearings will be inspected, measured, and replaced if possible to ensure the new camshaft will have proper support. Finally, camshaft bearing caps or girdle will be installed with new fasteners, and the engine can be reassembled. For pushrod type engines, the pushrods and lifters must be accessed by removing the intake manifold in many cases. Also, for many engines, the rocker arms must be completely removed, and the rocker arm studs will likely be rebuilt prior to installation of the rocker arms.