Are You Need a Valve Clearance Adjustment

It could, depending on the age, condition and brand of vehicle you’re driving. The maintenance schedules for some recent Hyundai engines, for example, call for a valve clearance inspection at 60,000 miles. Some Hondas call for an inspection at 110,000 miles. Some manufacturers advise valves should be inspected only if there is excessive valve noise. Others don’t mention valve clearance in their maintenance schedules.

Valves are opened by camshaft lobes on overhead camshaft engines and by rocker arms on pushrod engines. With extended time and use, the original clearances between these parts and the valve stems become bigger (with exhaust valves, the clearance can become tighter over time). That often leads to a clattering noise or more engine vibration that a driver might not notice for quite a while, because it increases gradually.

Intake valves open and close to let the air-fuel mixture (or just air in some modern engines) enter the combustion chambers, and the exhaust valves allow exhaust gases to escape. Too much or too little valve clearance can result in poor performance or a rough idle because the engine can’t “breathe” normally and operate at peak efficiency. Too much clearance means the valves will likely clatter and, over the long term, cause damage to the valves and/or camshaft lobes or rocker arms. If there’s too little clearance the valves won’t fully close, causing excessive heat, and the engine will lose power.

If your engine generates a loud clatter, it could be time for a valve clearance adjustment — though on some engines the valves don’t generate noise when there’s too much clearance. Loss of power could be a sign of a weak or broken valve spring, and a tapping noise could be caused by a loose rocker arm, so a clearance adjustment may not be all that’s needed. The mechanic won’t know for sure without inspecting the valves.

Because adjusting valve clearance (or “lash”) requires removing the valve cover (or covers on V-type engines) and checking both intake and exhaust valves, it isn’t a quick in-and-out maintenance item like an oil change, especially on engines that have three or four valves per cylinder. Plan on at least a few hours at the shop and a charge just for the inspection.