Features of the cylinder head design (VW Passat B4)

The cylinder head is cast from an aluminum alloy (Fig. 3-10). The seats, valve guides and pre-chambers (except for the "1Z" and "AFN" engines) are pressed into the cylinder head. Pre-combustion chamber type: Ricardo "Comet V".

Warning: The cylinder head cannot be ground.

The diameter of the holes for the valve tappets is 35.0-35.02 mm.

The diameter of the bearings for the camshaft journals is 26.0-26.02 mm.

The maximum permissible non-flatness of the cylinder head surface mating with the cylinder block is 0.1 mm. The valve seats are made of steel obtained by powder metallurgy and are pressed into the cylinder head. The characteristics of the valve seats are presented in Table 3-5. The valve guide bushings are made of bronze and are pressed into the cylinder head from above until they stop against the flange. At the lower end of the guide bushings there is a shoulder for installing the valve oil deflector caps. The overhead valves are installed in a row vertically relative to the crankshaft axis and parallel to each other and are actuated directly by the camshaft cams through hydraulic tappets.





The valve characteristics are presented in Table 3-6.

Note: Exhaust valves cannot be ground. They are only lapped.

The clearances in the valve drive mechanism are adjusted automatically by hydraulic tappets. Each intake and exhaust valve has two springs. The intake and exhaust valve springs are identical.

Length of springs, mm/under load, kgf:

• internal: 18.3/21-23;
• external: 22.3/43-48.

The tappets are made of hardened steel, ground and move in the cylinder head holes, acting on the valves through plungers. The cylinder head gasket is made of synthetic materials with a metal edging.

The original material is available on the portal (vwmanual.ru)

Depending on the amount of piston protrusion relative to the plane of the cylinder block, gaskets of three sizes are installed. The size of each size is indicated by the corresponding number of marks applied to the gasket (Table 3-7).

Note: If the pistons protrude by different amounts, the thickness of the gasket is selected based on the most protruding piston.

The five-bearing camshaft is installed in the upper part of the cylinder head. The axial clearance of the camshaft is no more than 0.15 mm.

The gap between the shaft journals and the support holes is no more than 0.11 mm.

The radial runout of the shaft journals is no more than 0.01 mm.

The intermediate shaft drives the oil pump and the brake booster vacuum pump. The axial clearance of the intermediate shaft is no more than 0.25 mm. Toothed belt of the brand and type Gates 6037 or Pirelli 135 RH 254. Replacement frequency:

• on cars with engines "1Y", "RA", "SB" and "AAZ": every 120,000 km;
• on vehicles with "1Z" and "AFN" engines: every 90,000 km.

The belt tension is checked using the VW 210 device on the branch between the toothed pulleys of the camshaft and intermediate shaft. The belt tension is considered normal when the indicator of the device moves by 12-13 divisions of the scale.