oil pressure drop once warmed up

[TurboWS6]

I had a very similar issue last year with my LQ9 pulled the motor and found this. My oil pressure was like 35ish cruising the highway hot. 45-50 cold at idle then 60 plus until it warmed up

Main bearing
[IMG][/IMG]
Notice how pretty much all the babbit material was gone, motor still had 35ish as stated above.

The culprit was the fact that the builder never put the bolt in the pickup tube to oil pump flange and the pickup tube slid out a little. All was good for about 25K miles then out of nowhere the oil pressure started dropping. Took this pick as soon as I pulled the pan. When I put it together this last time I used lock tight on that bolt just to be sure.
[IMG][/IMG]

Sorry man but your motor sounds like it doing exactly what mine was before I had the crank turned and put new bearings in. Its a PITA but you can pull it apart and fix it for probably 300 or so.

[Rattletrap]

Originally Posted by Pesce Nero

why not try 10-40 first?

how much pressure has been seen to be 'picked up' from 30w to 40w?

[blueyed tuner]

Check the GM Bulletins on the make and model of the engine. At one time there was a bulletin out that stated GM had some pumps with faulty relief valves. You would start engine up cold with good pressure and as the engine warmed the relief valve would stick open, as the engine would cont to warm to operating temp the oil gets slightly thinner and if the relief doesn't close slightly at this temp you have low oil pressure. When the engine cools the relief unsticks and closes so when time for the next start up your oil pressure seems to be normal. It will drive you insane. May not be the problem, but something to check I guess. I will check and see if I can find the bulletin info.

[Pesce Nero]

Originally Posted by Rattletrap

how much pressure has been seen to be 'picked up' from 30w to 40w?

i dont know because i have never put pee in my oil pan before. 5-30 just seems awefully low for any engine to me although i realize some of these newer motors call for that weight.

[Rattletrap]

Originally Posted by blueyed tuner

Check the GM Bulletins on the make and model of the engine. At one time there was a bulletin out that stated GM had some pumps with faulty relief valves. You would start engine up cold with good pressure and as the engine warmed the relief valve would stick open, as the engine would cont to warm to operating temp the oil gets slightly thinner and if the relief doesn't close slightly at this temp you have low oil pressure. When the engine cools the relief unsticks and closes so when time for the next start up your oil pressure seems to be normal. It will drive you insane. May not be the problem, but something to check I guess. I will check and see if I can find the bulletin info.

would this be the case on a new pump from 2011?

Originally Posted by Pesce Nero

i dont know because i have never put pee in my oil pan before. 5-30 just seems awefully low for any engine to me although i realize some of these newer motors call for that weight.

5w30 is recommendation from GM for these motors

[LXtasy]

Just shoot it

[bwelch]

I run 10w40 synthetic in my 5.3 with a "ton" of miles.

[jmd]

Originally Posted by LXtasy

Just shoot it

just what i would expect from you. lol

[blueyed tuner]

Originally Posted by Rattletrap

would this be the case on a new pump from 2011?

Well, that is a valid point. You would think they changed the way they make the new pumps. Well I was trying, maybe if or when you pull it down you can check and see if there are any signs of it sticking. I will make an effort to find that bulletin to see what years it covered.

5w30 is recommendation from GM for these motors

This is correct and usually if anything thicker is used it makes the valvetrain noisy, Just saying.

[gearmesh, inc.]

The old skool rule of thumb I always heard was that you need 10 psi of oil pressure for every 1k rpm you plan on turning. That would mean 70 psi for 7000 rpm.

Anyone have any other thoughts on this old skool rule of thumb?

[WILLIAMJRDN]

I know it doesnt help any but i'm running a high vol/ psi pump from LEP with 5w30 cold idle 50-55 and hot is 40-45. Garth told me i'de se higher if I ran through the stock system (14qt. system)

[Rattletrap]

UPDATE:
Cold OP is now 50, starts getting warm and goes to 40. Test drove it and did not go below 40 but have other problems which I think is in the tune and battery is not charging (which I knew) so when it dies it has to be jumped off....which I had to push it thru a 4way stop to a gas station and then walk 1.1 miles (since I didnt want to wake wife and 18MO from nap-such a nice guy).
Starts right up when hooked up to good battery.

This is a Melling High Pressure pump.

[WILLIAMJRDN]

Sounds good

[Rattletrap]

I have 2 thoughts about it:
loose engine should be fast but probably wont last long....