How to Eliminate Engine Valve Noiseby Jan Benschop
Most everyone who has owned a car has heard a clickety-clack coming from under the hood. The most common of such sounds emanates from the valve train of the engine. Some engines have rods pushing up on one end of rocker arms that push down on valves. The rods ride on cam shafts whose lobes time the valve movements. Some engines eliminate push rods by operating with overhead cams, reducing the mass and complexity of the valve train. Valves can stick, and so can rods. Diagnosing the noise wins half the battle.
Check the oil level in the engine; a level that's either too low or too high can cause valve noise. If either condition exists, take measures to correct it. If the oil is dirty, it can also cause valve sticking and cam lobe scoring. Change oil and filter immediately and see if the noise goes away. Observe oil and filter change intervals.
Remove the valve covers. Visually inspect all the valve springs; all of them should hold the rocker arms at the same height. If one of them rides lower, replace the valve spring.
Disconnect the ignition coil. Use a three-foot long bit of radiator hose held to one ear at one end to listen to valves at the other end. Have a helper crank the engine with the starter while you listen to each valve with the end of the hose held about half an inch from the mechanism. An unusually noisy clicking sound can indicate that the valve is sticking in its valve guide or that there is a worn spot on the camshaft lobe for that valve. It could also mean that the valve stem is bent, which requires valve replacement.
Pour some penetrating oil down the valve guide while it is operating. If the noise goes away, the problem is varnish buildup on the valve stem; using a better oil will cure the problem in time. If the noise stays, you may have a defective hydraulic lifter or cam follower that needs to be replaced.
Turn the valve spring half a turn with a wrench. If the noise goes away or changes, the valve most likely needs to be refaced. This requires head removal; if one valve needs it, more probably need it as well.
Once you have diagnosed and fixed the problem, replace the valve cover gaskets and reinstall the valve covers.
Items you will need
- dragster engine image by Robert Young from Fotolia.com