- Extraneous noise resulting from a malfunction of the hydraulic tappets occurs immediately after starting the engine and changes in accordance with the engine speed. However, this noise does not depend on the actual load on the motor. Therefore, if the noise does not occur immediately after starting the engine, if it does not change according to the engine speed or changes according to the engine load, then the hydraulic tappets are not the cause of the noise,
- In the event of a malfunction of the hydraulic pushers, the noise almost never disappears, even when the engine is idling after it has warmed up. The only time the noise can go away is when changing the engine oil (the knock of hydraulic pushers in this case is caused by the formation of sediment in the engine oil).
• Start the engine.
• Check that the noise appears immediately after starting the engine and that the noise changes according to the change in engine speed.
If the noise does not appear immediately after starting the engine, or if it does not change in accordance with the change in engine speed, the malfunction is not caused by a malfunction of the hydraulic pushers, look for another cause of the malfunction.
• When the engine is idling, check that the noise level does not change with the engine load.
• If the noise level fluctuates, it may be due to the collision of parts due to worn crankshaft bearings or connecting rod bearing shells.
• After the engine has warmed up, let it idle and check for abnormal noise. If the noise has decreased or disappeared, it is possible that the tappet noise is caused by contaminated engine oil. Wash hydraulic lifters.
• Remove air from hydropushers.
• If the noise does not disappear even after removing the air, clean the hydraulic tappets.
Removal of air from hydropushers
If the car has been on a slope for a long time or has not been used for a long period of time, the amount of oil in the hydraulic tappets will decrease, and air may enter the over-plunger cavity (1) when starting the engine.
If any of the above situations occurs, extraneous noise can be eliminated by removing air from the hydraulic pushers.
•Check the condition of the engine oil and top up or change it if necessary.
- If the oil level is too low, air will be sucked in through the screened oil intake and enter the oil passage.
- If the oil level is higher than required, the oil will mix with the air in the crankshaft and there will be a lot of air in the oil.
- If the oil is old, the air will not quickly separate from the oil, and the proportion of air in the oil will be increased.
- If air with oil gets into the over-plunger cavity of the hydraulic pushers, the air inside the over-plunger cavity will be compressed when the valve is opened, and the hydraulic pusher will not be compressed, which will lead to extraneous noise when the valve is closed. If air is removed from the oil, the operation of the hydraulic lifters returns to normal.
• Let the engine idle for 1-3 minutes to warm it up.
• Within 15 seconds, increase the engine speed to 3000 rpm, then reduce the speed sharply to idle and let the engine idle for 15 seconds, then repeat the cycle and check if the extraneous noise disappears. During normal operation, the sound disappears after 10-30 repetitions, but if after 30 repetitions or more the sound level has not changed, air inside the hydraulic tappets is not the likely cause of the extraneous sound.
• After the extraneous sound disappears, repeat the cycle 5 more times.
•Let the engine idle for 1-3 minutes and check that the sound has disappeared.