Valves and compensators — design description (BMW X5 E53)

The valves are made of special, corrosion-resistant steel, chrome-plated, in the form of hardened rods, which are located in the cylinder head in parallel. They are driven by the cams of the intake and exhaust overhead camshafts, through roller levers with supports on hydraulic compensators. The design of the intake and exhaust valves is the same. The diameter of the valve plate is 25.9 mm, with a valve stem diameter of 5.97^+0,01 mm.

One of the main engine indicators depends on the state of the valve mechanism – the compression value in its cylinders, which is checked with a special device, a compression meter, similar to gasoline engines. The rules for installing a compression meter and taking measurements are given in the instructions for the device and are described below.

The difference in pressure between the cylinders of one engine should not exceed 1.5 bar. If the difference is more than 1.5 bar or the pressure is less than 20.0 bar, this indicates increased wear of the piston rings, cylinder mirrors, and valves. Such an engine is subject to removal and repair.

Valve timing

The valve timing phases are 240° for intake and 228° for exhaust, and are determined with a calculated zero clearance between the camshaft cams and the drive lever, with a valve lift of 0.5 mm.

Hydraulic compensators

Hydraulic compensators are installed directly into the cylinder head body. The valves are driven by the camshaft cams through roller levers. Clearances in the valve drive mechanism are compensated automatically by hydraulic compensators.





Hydraulic compensators are self-adjusting and filled with oil (see fig. 3.8). A spring located in the tappet cylinder maintains the lever roller in constant contact with the camshaft cam.