you might have to replace the lifters.
Seafoam Motor Treatment.
Sometimes putting a jug of transmission fluid in your oil will clean the junk out of your lifters and stop your noise - if it is an older vehicle with adjustable rockers you can adjust and get rid of the knock.
To bleed the hydraulic lifters on a 2003 Opel Corsa 1.4, first, remove the valve cover to access the lifters. Submerge the lifters in engine oil and manually compress them to expel air, repeating this until no bubbles are visible. Reinstall the lifters, then reassemble the valve cover. Finally, start the engine and let it idle to ensure proper operation, checking for any unusual noises.
"Could you please stop making cat noises?"
have your valves adjusted adjust your valves
Hydraulic lifters are nonadjustable. Chances are the noise is coming from play in rocker arm, or ignition out of time. If you are sure it is the lifter, then it must be replaced.
eat something
If they are mechanical lifters, then there is an adjustment under the valve cover. If they are hydraulic then there is no adjustment, and while a different weight motor oil or special additive may help the ticking there is not real way to stop it.
The lifters are in the cylinder heads.The lifters are in the cylinder heads.
To bleed the valve lifters on a 1997 Opel Astra 180i Ecotec 16 valve, first, ensure the engine is cold and remove the valve cover. Submerge the lifters in engine oil and pump them manually to expel any trapped air. Reinstall the lifters, reassemble the valve cover, and then start the engine, allowing it to idle for a few minutes to ensure proper oil circulation. Check for any abnormal noises which may indicate that further bleeding is required.
either replace them or add motor honey to go for a longer perion without noise....