oil pressure drop when hot

[Shon]

Coming to you guys for some advise. I have not had this issue come up before LOL

Junk yard 6.0 from 2001 2500HD Silverado, mileage unknown, assumed LOTS.
replaced lifters, chain, and oil pump with new GM units.

Idle 40+PSI, rev it up get 60PSI. So I didnt think/notice any issues till I started driving it. Then noticed about 15-20min in the drive oil pressure is starting to drop. Just enough time for the oil to actually get heat in it and thin out (is my assumption). It drops to 20 at idle (or lower sometimes) and will not build past 30PSI.

F-body pan with Fbody diptstick/tube. oil is full. 5w30 non synthetic oil.

Thought if the o-ring was not seated right OP would not build at all.
I have read that some Oil pumps are bad out the box, not sure how b/c theres not much to them but it happens.

I am open to any and all suggestions before pulling front cover off and replacing the pump. Most research says that is the correct action plan. I do have the old pump here that can be used for a test.

Mechanical gauge.
All ears!

[TopFuel1966]

As you say, probably LOTS of miles. Try putting some 10-40 oil in it.

[BR3W CITY]

Are you loosing oil at all?


I'd say you can always do what I do when I have a REALLY old engine and just need to get it to survive.....Rotella 15w40. You will have oil pressure.

That being said, the 0-ring is always a suspect. Did you get a few different o-rings? Depending which pump, there is a blue, green and black o-ring and only one will fit correctly.

[Shon]

Originally Posted by BR3W CITY

Are you loosing oil at all?


I'd say you can always do what I do when I have a REALLY old engine and just need to get it to survive.....Rotella 15w40. You will have oil pressure.

That being said, the 0-ring is always a suspect. Did you get a few different o-rings? Depending which pump, there is a blue, green and black o-ring and only one will fit correctly.

All leaks are sealed. (except the shock, messed it up putting in so its puked everywhere).

I only recall 1 O-ring in the box from GM, I thought it was Green but that was months ago and I do not recall at all.

Rotella was mentioned before too LOL

[BR3W CITY]

GM Oil Pick-Up Tube O-Ring (1st Design)
12557752

BLUE SEAL
Specifics:

* Oil Pick-Up Tube O-Ring ea.
* Chevy/GMC Pick-Up (1999-2000 LS V8) 1st design
* F-Body (1998-2002)
* Cadillac CTS-V (2004-2007)
* Corvette (1997-2008)
* Thickness = 3.55mm (0.140")
ID = 23.60mm (0.930")



GM Oil Pick-Up Tube O-Ring (2nd Design)
12584922

RED SEAL
Specifics:

* Oil Pick-Up Tube O-Ring ea.
* Chevy/GMC Pick-Up (1999-2000 LS V8 engines with 2nd design pick-up tube)
* Trailblazer (2003-2008 With LS V8 engine)
* Hummer H2 (2003-2008)
* Hummer H3 (2008 With LS V8 engine)
* Chevy/GMC Pick-Up (2001-2008 LS V8 engines)
* W- Body (2006-2008 With LS V8 engine - Impala, Lacrosse, Grand Prix)
* Thickness = 4.20mm (0.165")
ID = 20.69mm (0.815")

[Shon]

Guess I need to pull the pump and tube and see what the specs are.

[Shon]

FYI-Melling High Pressure pump looks to have fixed the issue. but was unable to drive it much to really tell since I have battery charging issues and slight idle issues, left it on side of road and walked home LMAO

[BR3W CITY]

ooooh boy. whats happening, bogging or losing voltage or??

[Shon]

Volatge measured @ battery is 12.3V. @alt its 13.3. This @ idle with an UD crank pulley. Also this is in a mustang where the batt is in trunk. Going to test batt-old red top.
Posted via Mobile Device

[BR3W CITY]

Originally Posted by Shon

Volatge measured @ battery is 12.3V. @alt its 13.3. This @ idle with an UD crank pulley. Also this is in a mustang where the batt is in trunk. Going to test batt-old red top.
Posted via Mobile Device

Had that issue with mine this year, older yellowtop was reading 12+ at the battery, and alt came out near 14. Put the battery on a 8hr diagnostic charge, held less than 7v. I

[BR3W CITY]

Originally Posted by Shon

Volatge measured @ battery is 12.3V. @alt its 13.3. This @ idle with an UD crank pulley. Also this is in a mustang where the batt is in trunk. Going to test batt-old red top.
Posted via Mobile Device

Had that issue with mine this year, older yellowtop was reading 12+ at the battery, and alt came out near 14. Put the battery on a 8hr diagnostic charge, held less than 7v. Its also my experience that with a rear battery setup, you get less leeway on a low-bat since it takes the extra cca.