2006 Buick Lacrosse Oil Pressure and Leak?

[RreiS17]

I am hoping someone can help me or may have a similar problem with the engine for a 2006 Buick Lacrosse CX. Car only has 92,099 miles. Car was brought in to a local mechanic for oil and filter change. The lifters were making a ton of noise. Mechanic removed the covers and said there was oil in/on the lifters. Ran the engine with the cover off to see if oil is pumping onto the lifters. Nothing happened so the mechanic suspected the oil pump no longer was working. I had it replaced and had the filter and oil changed. Car ran fine for a day but then the lifter noise came back. And the oil light came on. Checked the oil level and it was hovering slightly below the bottom mark on the dipstick. (Previous check the oil level was right in the middle between the two marks). Added in a half a quart of oil, checked the level, all looked fine. Started the engine and it ran fine. Drove it the next day and the same problem occurred. There are no oil leaks on the ground. No black or white smoke coming out of the tailpipe. What could be wrong?

 

[MelsRegal]

The mechanic never checked the actual oil pressure before changing the oil pump?
You still have the noise?
How did the mechanic eliminate the possibility that the noise is from the timing chain?

 

[HotZ28]

In addition, you did not mention what engine the vehicle has/ so we have to make a guess? Is it a 2.4L- L4, or the 3.6L V6?