yes..it is possible for the oil pump check valve to be stuck open just a little to cause the low oil pressure
you may just want to replace the complete oil pump while you are there at it
OIL PUMP, PUMP SCREEN AND DEFLECTOR REPLACEMENTREMOVAL PROCEDURE
1. Remove the oil pan. 2. Remove the engine front cover. 3. Remove the oil pump screen bolt and nuts. 4. Remove the oil pump screen with O-ring seal. 5. Remove the O-ring seal from the pump screen. 6. Discard the O-ring seal.
7. Remove the remaining crankshaft oil deflector nuts. 8. Remove the crankiest oil deflector.
9. Remove the oil pump bolts. IMPORTANT: Do not allow dirt or debris to enter the oil pump assembly, cap end as necessary. 10. Remove the oil pump. 11. Clean and inspect the oil pump.INSTALLATION PROCEDURE
1. Align the splined surfaces of the crankshaft sprocket and the oil pump drive gear and install the oil pump. 2. Install the oil pump onto the crankshaft sprocket until the pump housing contacts the face of the engine block. NOTE: Refer to Fastener Notice in Service Precautions. 3. Install the oil pump bolts. Tighten Tighten the oil pump bolts to 25 N.m (18 lb ft).
4. Install the crankshaft oil deflector and nuts until snug.
5. Lubricate a NEW oil pump screen O-ring seal with clean engine oil. 6. Install the NEW O-ring seal onto the oil pump screen. IMPORTANT: Push the oil pump screen tube completely into the oil pump prior to tightening the bolt. Do not allow the bolt to pull the tube into the pump. 7. Align the oil pump screen mounting brackets with the correct crankshaft bearing cap studs. 8. Install the oil pump screen. 9. Install the oil pump screen bolt and nuts. Tighten 9.1. Tighten the oil pump screen bolt to 12 N.m (106 lb in). 9.2. Tighten the crankshaft oil deflector/oil pump screen nuts to 25 N.m (18 lb ft). 10. Install the engine front cover. 11. Install the oil pan.
how common is it that the check valve in the pump is stuck open? and is the oil cooler system thermostatically controlled or does it simply work off a bypass valve?
the cooler is open
it flows all the time
it isnt that common but it does happen
another thing that will happen sometimes on this year
is the o-ring on the pick-up strainer
it will break
causing the oilpump to suck air
ass long as the engine isnt knocking...i would think replacing the complete oil pump would fix your problem
ok, would you recommend replacing with a high pressure only or high pressure & high volume pump? and do you have any suggestions on best way to remove the oil pump on this vehicle? replaced pump on similar motor but in a sandrail car so i know its not exactly easy to get to the pump since the hummer has the front-flip hood...
i would just use an oem pump
it doesnt need anymore
unless you just want to add it
the pump isnt to bad to replace on this engine
it just takes a little time
i gave you instructions above on replacing it
wouldnt cause other complications if i did though correct? and ok, do you suggest removing the hood to have easier access or do you think it wont make a difference?
i always like removing the hood,,just to get it out of the way
and let in more light
but,,you really dont need to
no...a high pressure/volume would cause any trouble
ok good to know
alright, thank you for all your help. just wanted to check all my options before going and tearing into the motor