Oil Pressure Puzzler

[palallin]

Background:
2001 Tahoe, 4WD. 5.3 LS. 245,xxx miles.

Twice since the weather has gotten cold, I've had a scare. I start the vehicle to warm up, leave it for a moment, and come back to it to see the Oil Pressure Warning light on and the gauge reading near (but not at) zero. I shut it down. I check the oil. In both cases, it was less than completely full but oil was on the stick (the first time, just over a quart low; the second time, just under a quart low--oil consumption has been increasing). I topped off the oil.

At restart, the gauge comes up. It hits the 40 mark at idle as it warms up. The warmer it gets, the higher the pressure reads--which is the opposite of all other vehicles I've ever owned, which lose a bit of pressure as the engine warms up. At no time when the light was on did the engine make any noise, run at all rough, or indicate high temps. There are no after effects of any kind other than the wonky pressure readings.

So my puzzle is this: am I dealing with an oil pump problem, some kind of clogged passage, or a screwed up gauge? Does the gauge on these actually have pressure to it, or is it electronic?

Any input would be welcome and appreciated.

[MJN]

First thing I would check/replace is the screen that is located under the oil pressure sensor- if your Tahoe has active fuel management where it shuts down cylinders to save fuel- I can't remember if 2001s had that or not. Those get plugged with deposits over time and can starve the oil pressure sensor or reduce the flow to it. Probably a good time to replace the sensor as well while you're in there anyway.

[Hidesertchevy]

It's probably the oring on the oil pump pick up tube. Very common. No pressure when cold until the oring gets hot and expands. Very common!

[hatzie]

2001 doesn't have AFM.
That being said. The oil pressure senders are not GMs' most reliable engine sensor.
If it's the original part, your pressure sender is also not in its' first flush of youth at 20-21 years of age.

I'd change the oil pressure sensor out with a GM 12562267 or AC Delco D1818A and see what that gets you. These #s should be good for 1999-2002 5.3L & 4.8L pickups. If you go with Delco make sure it's the OEM grade or at least the professional grade part. RockAuto shows AC Delco OEM grade D1818A for $33.89

If the sensor resolves the issue then there's no reason to dig deeper.
Deeper would be the oil pump pickup o-ring and looking over the cam plate for leaks. Both will take an excursion behind the timing cover and into the oil pan to even look at.

[palallin]

Thanks for this info, guys. I'll need to figure out what's involved in getting to that sensor.

[Hidesertchevy]

Well after you swap the sensor and if still the same problem. 15$ oring on the oil pump pick up tube. easy job!

[truckdude239]

my 2002 suburban did this same thing it was the oring on the pick up tube repalced the orgin new pan gasket no issuse since!!

[heartattack]

Yep, oring on the pick up tube. The cold oil is thicker which cause the oil pump to suck more air around the oring than if the oil was hot and thin. I have done sevral of these.

[palallin]

Thanks again for the info, guys.

I can do the sensor but not the o-ring, so I will try that first and then talk to a guy with a shop, concrete floor, and lift about dropping the pan if needed.