Valve Train (Vehicles Build Up to 06/1999)

Both camshafts are driven by a shared timing belt, and operate four valves per cylinder by means of adjustable tappets. One spring on each valve is used to close the valve. The spring on the exhaust valve is marked with a blue paint mark, and the spring on the intake valve with a red one. The adjusting shims in the valve tappets can be changed to correct the valve clearance. These are available in 52 different thicknesses. The shim thickness is stamped on the back of the shim in hundredths of a millimeter (Example: the number 222 means 2.22 mm). Because of space limitations in the cylinder head the camshafts have to be removed before the adjusting shims can be renewed. This means that a high degree of accuracy is required during adjusting to avoid repeated removal and installation of the camshafts. The camshaft cams run concentrically on the valve tappets. At engine speeds of above about 3000 rpm this causes the tappets to rotate, and they in turn transfer the rotation to the valves. This valve rotation is required because it produces an even valve seating and prevents the valves from wearing in a certain position which could cause them to leak.