Regardless of the type of cam follower, wear is the most common trouble. Worn rollers will usually develop holes or pit marks in the roller surfaces. The mushroom type may develop a shallow channel when the cam

Figure 3-16.Adjusting valve clearance.

follower fails to revolve and the cams wipe the same surface each time the camshaft revolves. Normal use will cause surface disintegration, usually as the hardened surfaces begin to fatigue. The condition is aggravated by abrasive particles. Nicks and dents on rollers will also cause disintegration.

You must make constant checks for defective rollers or surfaces and for nicks, scratches, or dents in the camshaft. Whenever you find a defective cam follower, you should replace it. In roller-type cam followers you must replace a worn cam follower body and guide or roller needle bearings (if used).

Defective or poorly operating valve adjusters allow clearance or lash in the valve gear. Noisy operation of a lash adjuster indicates that there is insufficient oil in the cylinder of the unit. When you discover a noisy lash adjuster and the oil supply or pressure is not the source of trouble, remove and disassemble the unit according to the manufacturers instructions.

Since the parts of lash adjusters are not interchangeable, disassemble only one unit at a time. Check for resinous deposits, abrasive particles, a stuck ball check valve, a scored check valve seat, and excessive leakage. Carefully wash all parts of the hydraulic lash adjuster in kerosene or diesel fuel. Check such parts as the cam follower body, plunger or piston, and hydraulic cylinder for proper fit.

Figure 3-17.Removing an individual cam.