2. The valve train noise is usually due to the excessive clearance two internal engine parts such as a broken valve spring or a worn out camshaft lobe.

3. The sound frequency of the valve train noise is one-half the crankshaft speed and a clicking lifter is a common valve train noise.

4. The problem with diagnosing and correcting valve train noise is that there are many components that can cause undesirable sounds.

5. Here are the usual four types of noise that comes out of an inoperative or failing valve lifter.

7. This noise can be the result of excessive varnish, wear on the bottom of the lifter mat and excessively fast or slow leak down.

8. Slow leak down generally will cause the engine to be noisy only when cold and the oil is thick.

9. With a fast leak down, the valve train will be noisy when the engine is warm and the fast leak down will also occur if the ball-check in the lifter fails to seal.

10. The noise level depends on the amount of varnish and the degree of wear.

12. A stuck plunger inside the body of the lifter could be the reason of the sound and this is usually due to excessive varnish between the plunger and body.

13. Even the presence of dirt or other foreign materials wedged between the plunger and body causes such sound.

14. Another cause of a loud rapping sound is an excessively worn base or foot on the lifter itself.

16. When the sound is throughout the entire valve train, the cause is usually the weight of the oil or the oil supply itself.

17. Too much oil in the crankcase will cause foaming and aeration as a result, when air gets into the lifters, they will fail to operate properly.

18. Insufficient oil supply to the lifters can also cause general valve train noise and this could be the result of too little oil in the crankcase or clogged main oil gallery lines.

19. Excessively thick engine oil will cause entire valve train noise when cold-starting an engine and the noise will diminish when the oil warms up and starts to flow properly.

21. This type of noise is hard to locate as there will be a few clicks, and then it will be quiet, but the noise will reappear after a short period of time.

22. The usual cause of intermittent clicking is a very minute piece of dirt that holds the ball check off the seat for a few seconds and then passes through.

23. In rare cases, the cause of the sound is a pitted or flat spotted ball-check.

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