Before disassembling any part of the engine to correct lifter noise, check the oil pressure. If the vehicle has no oil pressure gauge, install a reliable gauge at the pressure sending-unit. The pressure should be between 207-552 kPa (30-70 psi) at 3, 000 RPM.
Check the oil level after the engine reaches normal operating temperature. Allow 5 minutes to stabilize oil level, check dipstick. The oil level in the pan should never be above the FULL mark or below the ADD OIL mark on the dipstick. Either of these two conditions could be responsible for noisy lifters.
HIGH
If oil level is above the FULL mark, it is possible for the connecting rods to dip into the oil. With the
engine running, this condition could create foam in the oil pan. Foam in oil pan would be fed to the
hydraulic lifters by the oil pump causing them to lose length and allow valves to seat noisily.
LOW
Low oil level may allow oil pump to take in air. When air is fed to the lifters, they lose length, which
allows valves to seat noisily. Any leaks on intake side of oil pump through which air can be drawn will
create the same lifter action. Check the lubrication system from the intake strainer to the pump cover,
including the relief valve retainer cap. When lifter noise is due to aeration, it may be intermittent or constant, and usually more than one lifter will be noisy. When oil level and leaks have been corrected, operate the engine at fast idle. Run engine for a sufficient time to allow all of the air inside the lifters to be bled out.