If knocks are heard in the cylinder head, then this is evidence of a malfunction of one or more hydraulic tappets. Knocks in the valves are also possible with serviceable hydraulic tappets. But this is possible:
- A) immediately after starting the engine. The reason for the appearance of knocks in this case is the insufficient supply of oil to the hydraulic tappets at this stage of engine operation.
- b) while the engine is running, if the vehicle has previously been exposed to high external temperatures for a long time.
- V) when starting the engine after a long stay in the parking lot or not in operation. As soon as the engine warms up, these knocks will disappear.
- G) at a very low oil level when the oil pump «sucks» air.
1. Start the engine and let it idle until the radiator fan turns on.
2. Increase the engine speed to about 2500 rpm. and let the engine run for approximately 2 minutes at that speed.
3. Shut off the engine if the engine noise does not stop.
4. Remove the cylinder head.
5. Set the piston of cylinder No. 1 to the TDC position.
6. Push both poppets of cylinder #1 down with a wooden wedge. If at the same time there is a play higher than 0.1 mm, then replace the pushers. The pusher cannot be repaired (see illustration).
Attention! Do not use metal tools when performing this operation, so as not to damage the pusher.
7. Repeat the same procedure with the pushers of other cylinders, setting the piston of the cylinder of the tested pusher to TDC. In this position, on the cylinder being tested, the camshaft cams are facing up.
8. Remove the camshaft.
9. Remove the pusher.
10. Lubricate the guides of the new pusher with fuel and install the new pusher in place.
11. Install the camshaft in place.
After installing new poppets, the engine should only be started after approximately 30 minutes. The pushers must «sit down». Otherwise, the valve and piston may collide.
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