Hi,
I have long used this forum for advice on repairing my suburban but couldn't find this information anywhere so I registered so I could contribute my experience.

2001 Suburban 5.3L Vortec with 201K miles

The initial symptom that started this process is one cold morning I started my Suburban and I got the low oil pressure message. The dashboard gauge showed zero psi but after a long few seconds it jumped off zero. The engine was noisy for several seconds until the oil pressure came up so I never doubted the gauge. I continued to drive the vehicle through a couple winter months and the issue became progressively worse to the point that I had to keep the engine rev'd above ~1200 rpms until the engine temp reached 160F and then the oil pressure was ok. Also, I had to rev the engine a couple times just to get the initial pressure started. I only got zero oil pressure if the vehicle had sat overnight and it was cold <50F.

I guessed that the oil tube pick up o-ring was allowing air into the oil pump making it difficult for the pump to suck the oil out of the sump. I replaced the o-ring and the problem was solved. You access this o-ring by dropping the oil pan.

The old o-ring was hard and deformed/flattened. After replacing the o-ring my idle oil pressure is ~40 and the cruising oil pressure is between 50-60. Before the o-ring replacement it was ~20 at idle and ~40 when cruising. Another symptom I saw that I think was the earliest indication of this o-ring failing was the oil pressure gauge needle wiggling with small oscillations during the preceding summer months. After replacing the o-ring the gauge's needle is steady.
Regards,
TooTall

 

Thanks for the info. I have a 2008 Suburban that I had a oil pump replaced on this past summer. Oil pressure was fine until this past week when temps dropped to -17 degrees here in Michigan. I was thinking that the oil pressure relief valve was part of my oil pressure drop. I will drop the pan and replace the O-ring that was probably squashed by the mechanic at the dealership. Either way, my 5.3 l engine has the same symptoms you describe. Worst type of weather for it to happen in.

 

Even before I can drop the pan and replace the O-ring I oil pressure drops to 20lbs upon exiting the expressway last night. Get in driveway and notice lifter clatter. Not a good sign. Anyway, start Suburban up this afternoon and their is 40 lbs oil pressure after a few seconds of idling but still the lifter clatter. Seems it's the same symptoms you explained. But, I feel I may have a damaged lifter now. Did your engine clatter until you replaced the O-ring?

 

My clatter (sounds kind of like a diesel engine in the cab) happens for the first 30-60 seconds of operation after sitting overnight. I guess all of the oil drains out of the worn lifters and it takes a little while to re-pressurize them. Replacing the oil pump pickup tube o-ring did soften this symptom but the engine still has intial clatters after sitting overnight. After the initial clatter subsides, there is still some constant abnormal engine noise (which almost sounds like an exhaust leak pop) but it can only be heard if you are outside of the cab.

 

The clatter in my valve train has gone away after engine warmed up. Pressure still drops after engine temp is at normal range and been running for a while. Will be ordering O-ring and new gasket for pan to resolve problem as you identified. Haven't checked service manual yet, but my Suburban is a 4 wheel drive and I am curious if anything is restricting the removal of the oil pan in the process of taking it off. Going to be doing the work laying on my side and back so I would like to be prepared and not find any unexpected delays.

 

Have fun! The entire front drive assembly is in the way. That's why I haven't replaced my oil pan gasket. The oil pan has the slightest leak, but, it looks like a PITA to do. Brother in law looked up the job specs in his books, he simply said its a nightmare, don't bother.

But good luck to you on your oil pan project...

 

Thanks for the info on the bottom side of engine. You are definitely right about what has to be done just to change out the O-ring on the oil pick-up tube. So, prior to attempting that work intensive job, I did a oil and filter change. Took about a half-hour and I replaced a Auto-zone Micro fiber filter with a Mobil-1 filter. It was the first time I ever used that Micro-fiber brand. Needless to say it was the demon behind the low oil pressure. I have always used Valvoline Synthetic Blend with no problem and Tough Guard Fram filters. But from this point on I will begin the continued use of Mobil-1 brand oil filters. My pressure stays between 35 and 60 pounds depending on whether I am sitting in drive at a stop light or moving at highway speeds. Either way, I am back on road with less stress.

 

Been a little over a week since I did the oil filter and oil change on the engine. I can definitely say that I will not have to change the O-ring on the pick up tube. Oil pressure has been between 30 and 60 pounds depending on engine rpm. I believe the oil filter was the demon creating the super low oil pressure. Will never use off brand oil filters again.