Very low oil pressure on cold starts.
 

My 2008 Impala SS has been throwing code P0521 for about 5 months now. After replacing the pressure sensor three times and the filter under It, I just Ignored It. Until recently It started happening anytime I would remote start It In the morning and shut Itself off. The other morning I remote started It and came outside to It ticking enough to say oh sh*t. Why did It not shut off, Idk. But luckily It was the heads ticking and not the bottom end and went away soon as I started driving. So I decided not to Ignore It anymore and get It fixed asap. On my superchips tuner It has a gauge for oil pressure and on cold starts Idling It ranges from 5-15 PSI. If you hold It around 1500 RPM It's fine and has 40+ PSI or just start driving right away, which I don't like doing In 10 degree weather. But once It warms up a little It's fine and never loses pressure until the oil gets cold again. So I determined It's the common oil pump pick up tube o ring. On the Impalas whats Involved In replacing It? I heard you have to lower the engine cradle. Hopefully there's a way around that, If not I'll have to pay a shop. Is there any step by step Instructions? Thanks. Oh yeah It just hit 150k and not one single problem except this one.

Did you keep the oil and filter changed regularly? When you change your oil do you examine it to see if there's any metal shavings? With 150,000 miles on it I'm sure things are beginning to loosen up and oil pressure will get weaker as a result. If you've been neglecting your oil changes it can lead to sludge buildup in the engine and this will gum the oil filter up sooner and this can cause an oil restriction and lower oil pressure. What kind of oils are you putting in the engine? They should be getting a synthetic oil and 5W30 is recommended but in the summer when it gets hotter running a thicker oil like 10w30 is not a bad idea. Also typically on cold starts your engine oil pressure is at its highest until the engine has had time to heat up and you should see your pressure go up as you accelerate not fall. Might not be a bad idea to start cutting your oil filters open to examine the filter element and see if your seeing any signs of metal that may point to a bearing issue.

The engine Is clean as Idk what Inside. I run Castrol Edge 5w30 Full Synthetic and change It when It gets down around 40%. The engine Is definitely not worn out. As most of this Is highway miles because of my job. But 5-10 PSI on a cold engine Is definitely not normal.

You're probably right on the o-ring. I have the same problem myself right now. With a broken o-ring think of it like trying to drink through a straw with a hole in it. Now with cold, thick oil, think of trying to drink a milk-shake with the same straw versus a soda. Takes more effort (higher rpm) to pull shake through than it would the thinner, hot soda. Anyway, Everything I've seen is that you have to drop the cradle to get the clearance to get the pan off. Here is an old sticky from another site that walks you through a gasket replacement. Once you are that far it should not be too difficult to get the strainer off and replace the o-ring then button it back up. I haven't done it my self yet since I work outside and I'm waiting for the weather to break but I'm to the point it has to be done. It ain't gonna heal itself. The thread is so old the photos won't show anymore but should give you an idea of what it takes. We just have to face it, our cars are niche cars with a dying market. It's getting harder and harder to find internet help cause the forums are drying up. This is the only one that has had any post in about the last year and don't forget to give up any hope for any new performance parts for this chassis. If it doesn't fit a Camaro or a pick-up truck too then give up hope of anything new. Our market is going the way of the do-do. It's a shame because these are really great cars.

Here's the link:
http://www.gmls4.com/index.php/topic,1610.0.html

Those Instructions make It look really easy. The only thing that may give you trouble Is the rear cradle bolts. As long as you don't have to remove the rack and pinion I may try and do It myself when It warms up a bit.

Seems like I saw some where that you may have to unbolt the rack from the cradle but you didn't have to unbolt the rod ends.
I'm in NC so along with the temperature I've also got to deal with this rain that we've been having. I can't hardly remember when we've had a streak of more than about 3 days without rain.