2003 Chevy Suburban Occasional Zero Oil Pressure at Startup

TXKAWBOY

MEMBER
2003 CHEVROLET SUBURBAN
V8
2WD
AUTOMATIC
98,000 MILES

FYI: I dontaed via jonkristo on paypal!

Problem: Often upon startup, you will have NO oil pressure---clattering lifters verifies that the gauge and dummy lite is correct.

1. 2003 Vortec 5.3L, 5300 Z (E85 fuel), bought used from one-owner with 78000mi, and it now has 98000mi. Runs perfectly, 18mpg on the highway.
2. Never had a seconds problem until this Saturday:We had driven it only 5miles down the road with a carload of adults, to look at a house. I shut it off for 40mins.
I then started it in order to go back home.
Immediately at startup, the dummy was dinging loudly, and the oil gauge showed ZERO, and the lifters were clattering.
It sat there for ~20 or 30seconds, (while I was in disbelief), until I revved it gently to ~1500rpm---instantly pressure returned to normal at idle, and lifters hushed instantly.
3. Since then, it has done it randomly 2 more times, always after having sat idle for at least 3hrs.
4. Each time, if you rev it up once to ~1500rpm, it will instantly began working, and the lifters, etc, will all hush as the oil hits them. Oil pressure is normal, even at idle.
5. I changed the filter and oil back to conventional Rotella, started it stone cold, but it STILL has no pressure, so I immediately shut it off and WROTE YOU GUYS!

"Side Notes/Clues": When I switched to the synthetic, my oil pressure increased tremendously, almost by an additional 18psi at 70mph on the highway (it will read 60+ psi). Could this have anything to do with the oil-pump/oil-pump check valve?

I have always used conventional Rotella 15w40, but last oil change I used Rotella 5w40 SYNTHETIC---and the car's "dummy lite" did not tell me to change the oil until only two days prior to this "no oil pressure" problem---and the synthetic oil had a staggering 8,000 miles on it/filter! That is the last time I rely on the "dummy oil-change lite".

Thanks a million guys! My one solitary dealer in this town does not know much more than me, and that is at $65hr!

5 Replies

MATHIASO

MECHANIC
1,209 POSTS

Thank you txkawboy for writting to us.
what I like about a car like your chevy is that when there a problem, the computer shut the system off so the engine won't be damage. you did right thing not to drive the car until you figure out what is going on.
there two components that I will be talking about., that is the oil pressure sensor and the oil pump.

oil sensor

Testing

Check the oil level and correct as necessary. Turn the ignition switch on, but do not start the engine.
Disconnect the sensor lead at the sensor. The gauge should read full scale.
Ground the connector. The gauge should read at the bottom of the scale.
If the gauge functions properly, replace the sensor.
if you need to remove the sensor, just let me know, I'll guide you.

if the the sensor and connector is good the last place to look will be for a faulty oil pump.

Inspect the oil pump housing and the cover for cracks, excessive wear, scoring, or casting imperfections. Inspect the oil pump housing-to-engine block oil gallery surface for scratches or gouging. Inspect the oil pump housing for damaged bolt hole threads. Inspect the relief valve plug and plug bore for damaged threads. Inspect the oil pump internal oil passages for restrictions. Inspect the drive gear and driven gear for chipping, galling or wear. Minor burrs or imperfections on the gears may be removed with a fine oil stone. Inspect the drive gear splines for excessive wear. Inspect the pressure relief valve and bore for scoring or wear. The valve must move freely in the bore with no restrictions. Inspect the oil pump screen for debris or restrictions. Inspect the oil pump screen for broken or loose wire mesh.