Originally Posted by singscountry1967
I got to wondering...what causes a lifter tick? Well...besides a "bad lifter"...I guess the correct question is what causes a lifter to "go bad"? I have this same noise...always have (bought in Dec 04 with 31k miles).
First, lifters don't "tick"...the ticking noise is caused by slack in the valve train for some reason..the lifters can't follow the cam lobes and you hear the slack comming out of the valve train every time a valve gets lifted off it'* seat. (frequencey of one bad lifter/valvetrain is 1/2 engine rpm) So the real question becomes "Where did the slack in the valvetrain come from ?"
A coolant leak into the oil can cause it. Take a look at the rebuild thread I've been doing. That milkshake lookin Latte colored sludge found in the oil passages was the engine oil mixed with DexCool. It was so thick that it glued parts together. The lifters themselves were so full of it that they couldn't pump oil and collapsed. To get them apart, I had to soak them in solvent, then pump the sludge out by repeatedly pumping them in the jaws of a vise till they would come apart. It actually didn't harm them, but I don't know how long this motor suffered before being sold to me.
Without a coolant leak, the other things that can cause a ticking noise in the valve train are:
1.) Excessive wear inside the lifter (The lifter has a piston in it that pumps oil, if it wears out, oil gets squeezed past the piston instead of being pumped up inside the pushrod.) This is likely a defective lifter from the get-go. The parts inside the lifter are hard chromed and wicked tough surfaces. Without something metallic getting inside the lifter, it would be rare for one to fail mechanically.
2.) Busted piston return spring inside the lifter (has the same effect as #1)
3.) Bent pushrod...but that raises the question of what happened to cause the pushrod to bend. It can happen. The pushrod is nothing but a steel tube with a hard chromed steel ball at each end. They should have been perfectly straight from the factory, but sometimes aren't. If they have even a slight bend to them, they will flex or bow with every cycle. Sooner or later, they get softer from fatigue and stop springing back to shape.
4.) Excessive wear between the lifter bores and the lifters. (not enough oil is going inside the hole in the lifter body, it'* all going around the outside of the lifter. You would also have abnormally low oil pressure on this one.)
5.) Busted Valve Spring. A busted valve spring is the real dangerous failure because the valve is no longer being forced back into the seat. Should it drop low enough to get hit by the crown of the piston it'* toast.. That will usually drive the retainers out and allow the valve to drop down into the cylinder. In other words: kiss the piston, cylinder bore, and head good-bye.
6.) Worn out cam lobe. This gets ugly fast cause once you are through the hardened surface of the cam, the softer metal inside will wear really fast until the cam lobe isn't a "lobe" any more...and the missing metal is down in the oil pan.
7.) Loose rocker nut. It wasn't tighted up enough to start with, the stud has stretched, or in the case of older motors, the stud has been pulled out of the head.
8.) No or Low oil pressure from the pump...root cause of most engine problems.
Hope that helps explain where the "ticking" noise comes from