When the clearance is reduced, the valve timing changes, the cylinder sealing deteriorates, engine power drops, and it starts to run intermittently. In extreme cases, the valves or their seats become deformed or burn out.
When the gap is increased, loud noises arise, the valve timing changes, the engine loses power due to insufficient filling of the cylinders, and its operation becomes uneven.
Due to differences in the coefficient of thermal expansion of different parts of the engine, the thermal clearance of the valves also depends on the operating temperature of the engine.
Caution! Valve clearances must be checked and adjusted on a cold engine.
Valve clearances should be checked every 10,000 km. The nominal clearance values for all vehicle variants are as follows:
- intake valves - 0.15 mm;
- exhaust valves - 0.15 mm.
Raise the rear of the vehicle and place it on supports.
[The original text can be found on the portal: vwmanual]
Using a large screwdriver, remove the retaining clips on the valve cover and remove the cover.
Adjustment of thermal valve clearances is performed in the following sequence: 1st, 2nd, 3rd and 4th cylinders. The first cylinder is located at the front right side as the vehicle moves. The corresponding marking is located on the engine cover next to the spark plug hole.
The clearance must be adjusted when the piston is at TDC on the compression stroke. In this position, both valves are closed.
Set cylinder 1 to TDC. To do this, remove the distributor cap and crank the engine using the V-belt until the mark on the pulley aligns with the joint between the crankcase halves. At the same time, the middle of the movable contact of the distributor must coincide with the mark on the edge of the latter's housing. In this position, the thermal clearance of the valves of the 1st cylinder is checked and adjusted.
Insert a 0.15 mm feeler gauge between the valve rocker arm and its stem. If the valve clearance is greater or less than the nominal value, loosen the adjusting screw lock nut and adjust the clearance using a screwdriver. The gap is set correctly if the feeler gauge is inserted and removed with little friction.
While holding the adjusting screw in the proper position with a screwdriver, tighten the lock nut.
Check the valve clearance again. To adjust the thermal clearances in
valves of other cylinders, it is necessary to set the piston of the corresponding cylinder to TDC by rotating the crankshaft. Adjustment is made much easier if you use a scriber to make appropriate marks on the edge of the distributor housing.
To adjust the valve clearances of other cylinders, the crankshaft must be installed according to the markings shown in the picture, each time turning it to the left at an angle of 90°.
Wash the valve cover with gasoline, install a new sealing gasket and secure the cover with a clamp.
Check the oil level and test drive to see if the valve cover gasket is leaking oil.
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