I need help. Last week the low oil pressure light came on when at idle in my 07 Silverado took it to dealer and they told us it was the oil pump. We replaced it with no luck still low oil pressure then we got the oil sending unit changed still no luck. We have since hooked up a oil gauge to it still we have very little oil pressure. There is no engine noise. what could be wrong.

 

Welcome to the forum. How low is "very little oil pressure" on the gauge they hooked up? Did they drop the oil pan and check things over (oil pickup and oil pressure relief valve)?

P.S. Oh, I see they did drop the oil pan. Still, they probably should have replaced the oil pressure relief valve while they were at it.

 

The oil pressure is only 8-10psi at idle when warm, they are now dropping the oil pan. Do you think it could be the oil pressure relief valve?

 

If this were warranty work, disregard the rest of this post. Now, not knowing this vehicle's history, mileage, general condition, not even the engine displacement, I can't say "8-10psi at idle when warm" is that alarming, especially in the absence of "engine noise." If it read higher pressure as the engine RPM went up, oil pressure relief valve wouldn't be a suspect. The low reading (again, not alarmingly) can be from general engine wear (nothing you can do about) or sludge in the right places. If it were my money, I wouldn't have put down a large chunk on a new oil pump. Rather, I'd have tried an oil change with a high detergent synthetic oil first. My favorite is Pennzoil Ultra which is arguably the best there is in dissolving sludge safely, i.e., without dislodging chunks.

 

I have found that GM states 6psi for every 1000rpm is ok
Could be you crank case is not sealed
There is a plug behind the timing cover, and a "barbell restrictor" behind the rear cover that plugs he oil galley
Also could be a spun bearing