Originally Posted by bdja
I bought a 2000 GMC Sierra, new 10 years ago and just started to have lifter noise. The original motor has 323,000 miles on it and would love to keep it. Is the noise a sign of bad things to come? Thank you.
The engine could have oil flow issues from carbon build up in your engine's oil journals. Try adding a liter of Marvel Mystery oil in to your crank case and then 1/2 liter of Marvel Mystery Oil to your next oil change.
The Marvel Mystery oil will dissolve the carbon though out your internal engine components. Make sure you keep an eye on your engine oil level while the Marvel Mystery oil is in with your engine oil.
If your luck the lifter noise was the caused of carbon restricting the oil flow into the lifters. The other thing that would cause your lifters to be noisy would be a worn cam shaft. Start with the simple and add a liter of Marvel Mystery Oil which can be found at Auto Zone.
Good luck and keep me posted. Be glad to help you keep your engine running 100%