The first cause of the knock is the lifters getting air in them mudpluggers cavity. Typically, this occurs in two cases: if the engine oil level in the crankcase is on the upper level or lower level. The same situation may occur after a long Parking the vehicle on an incline.
The second reason is the appearance of impurities on the precision surfaces of the hydraulic compensators. These pollutants can be formed by a sludge engine oil of very low quality or old oil, don't replaced in time. In addition, debris may fall from damaged oil filter.
The third reason is the premature wear of the lifters. Typically, this occurs as a result of factory defect.
The nature of the noise of the lifters, you can define the method of its elimination. If the noise occurs immediately after starting the engine and during warm-up it Yes operating temperature disappears, necessary cleaning and flushing of these devices. If the noise does not appear immediately and with increasing speed does not change, look for its cause in any other parts of the motor, not the hydraulic lifters. They are OK. The sound is background noise, appear immediately after starting the engine and changing the tone and strength depending on the momentum signals the failure of the expansion joint. They must be replaced as they are sealed and cannot be repaired.
The elimination of trapped in the lifters of air without lifting them is as follows. Check the oil level and fill if necessary. Start the engine and warm it. Dramatically increase the speed to maximum and immediately reduce to idle. Repeat up to 30 times with 15-second breaks until until knock disappears. After achieving the desired result, do this 5 more times and continue running the engine at idle for 3 minutes. If the result is not achieved, clean the lash Adjusters.