Valve Clearance Inspection / Adjustment

GENERAL INFORMATION

Clearance must be provided in the valve train to compensate for different thermal expansions.

If the clearance is too small, valve timing changes, compression decreases, engine power drops, and engine operation becomes uneven. In extreme cases, the valves may be damaged, or the valves and seats may burn.

If the clearance is too large, loud mechanical noise occurs, valve timing changes, and the engine produces less power due to insufficient cylinder filling, and engine operation becomes uneven.

Valve adjustment achieves the desired result only if the valves seal perfectly, have no excessive play in the guides, and the valve stem ends are not damaged.

Valve clearance must be checked and adjusted after repair or when noise appears in the valve train. Valve clearance does not need to be checked as part of routine maintenance. The diesel engine 2 L has hydraulic lash adjusters that automatically maintain valve clearance. Valve clearance on these engines is not adjustable. If abnormal noise occurs in the valve train, inspect the hydraulic lash adjusters (performed at a workshop).

Valve clearance must be checked or adjusted on a warm engine; however, it can also be adjusted on a cold engine. In this case, it must be checked again on a warm engine.

Test conditions

PROCEDURE

1. Start the engine and warm it up until the coolant temperature reaches 80°–90°C.

2. Stop the engine.

3. To make the work easier, remove the spark plugs.

4. Remove the cylinder head cover.

5. Place the transmission in neutral and apply the parking brake.

6. Turn the crankshaft so that piston No. 1 is at top dead center (TDC).

7. At the same time, piston No. 4 must be at TDC. Cylinders are numbered from right to left. Cylinder 1 is located on the drive belt side of the engine.