2005 Tahoe. 5.3 oil pressure?

[The Griff]

I found this Tahoe for sale just outside my little town, I didn't really have any intention on buying it, but my mom was in need of a new vehicle and I showed her a picture of it, and she fell in love, so i went back over and bought it.

Two weeks later mom passed away, she never got to drive it.

I've decided that I'm keeping it, it's probably the nicest thing I've ever owned, but it's got a few little issues that need dealing with.


It's an 05, with a 5.3, 4L60E, Autotrac, 3:42 gears, and 230k miles.

It came with a stack of receipts for everything from wheel bearings to a water pump to a whole new transfer case, all within the last 6 years.

It feels like it's brand new, no squeaks, no wind noise, everything works, from the heated seats, the sunroof and even the DVD player.


However, I feel like the oil pressure should be higher, cold idle is around 25, warm around 10-15, and never gets above 40 at speed. Shifting from drive back to park it will briefly drop down around 5 before coming back to the 15-20 range.

Compare that to my 220k mile 2000 LQ4 6.0, which idles around 40 lbs and and is north of 60 lbs at speed.


My sister has an 07 5.3 Tahoe with 240k and her oil pressure is basically the same as my 5.3. She also has an 03 1500HD with a 6.0, that behaves just like my 6.0.

A guy I work with has a 99 half ton with a 5.3, whose oil pressure is roughly the same, 20-40.

Do the LQ4s have a higher pressure oil pump than an LM7 5.3? Its not low enough to be a problem, but it gets my attention every time I see it.

 

[Babaganoosh]

Dang that’s a splitting image of my 05, sorry to hear about your mother.

I would put money on the o ring from the pickup tube into the oil pump. Also might be worth to toss a new sending unit but it’s usually the pickup tube.

 

[HBD]

I would agree with the pick up tube o ring replacement. I have an 02 with 255000 that only held 18-20 lbs oil pressure once warm. Changed that o ring and a new oil pump. Now it runs 45-50 warm idle plus I think it runs better and smooth and quiet.

 

[Chevy305]

I've never tried this but I've heard of an Easy way to tell before investing in dropping the oil pan is to fill the the engine with double the amount of oil so the pickup tube is submerged in oil. Only run it for a min or less. Enough time to take an oil pressure reading and then shut it down drain out the extra. If the oil pressure jumps up to a more normal range the o ring is the issue. If it doesn't then you're looking at a larger engine issue.
Makes sense on paper but again I've never tried it.

 

[Truckman4life]

Fyi...the oil pump can be done without pulling the pan if you are a patient person and very careful with the pickup tube bolt.

 

[6872xtc]

Sorry for your loss.

Does the oil pressure gauge seem to work well? I am wondering if the stepper motor may have a slight influence AND it needs a new O ring on the pick-up tube.
I would be tempted to swap the clusters between the truck amd the Tahoe to compare, IF you question the gauge at all. I saw an '04 Escalade that had the gauge issue. It wouldn't read consistently, but it didn't follow rpm much.

I personally would be more inclined to pull the front diff out and pull the pan so that I could clean it out. But the work to move the steering box forward and pull the front diff out isn't exactly fun. At least that's how I had to do it on my 2500HD. I didn't have to drain the coolant, so I avoided that mess.

This doesn't get you a new pump, though, which may or may not be what you want.

 

[Blue85]

The other simple variable is the oil pressure sender. I had one fail on a 5.3 and grabbed a new one from Autozone (was out of town) and the pressure has read easily 5psi lower since then. My son had a gauge that would kind of wander around randomly, then the sensor started to leak and a new sensor made it stable.

If you're pulling the sensor, that's also a good time to verify with a mechanical gauge.

There's really no expected pressure difference between the various flavors of LS-Vortec of that era.

 

[The Griff]

Sorry for your loss.

Does the oil pressure gauge seem to work well? I am wondering if the stepper motor may have a slight influence AND it needs a new O ring on the pick-up tube.
I would be tempted to swap the clusters between the truck amd the Tahoe to compare, IF you question the gauge at all. I saw an '04 Escalade that had the gauge issue. It wouldn't read consistently, but it didn't follow rpm much.

I personally would be more inclined to pull the front diff out and pull the pan so that I could clean it out. But the work to move the steering box forward and pull the front diff out isn't exactly fun. At least that's how I had to do it on my 2500HD. I didn't have to drain the coolant, so I avoided that mess.

This doesn't get you a new pump, though, which may or may not be what you want.

I'm not 100% convinced that the guage is accurate, it'll hold steady at 40 lbs at 1800 rpm, but sometimes stay there even after you've come to a stop in gear around 700 rpm. But sometimes when you put it in park it'll drop to almost nothing, before it bounces back.

I know these trucks are notorious for stepper motor problems, but all the guages work, or at least appear to work in the Tahoe, as well as all the other GMT800 trucks I've had.

I've thought about swapping clusters, but my 6.0 truck is a 2000, and has a slightly different cluster from the 03-07 trucks. I could try the cluster from my 04 Duramax, but they have a 120 psi oil pressure guage, whereas the LS trucks only went to 80, I'm not sure if the reading would be accurate.

 

[Truckman4life]

They make great derby car engines cuz they don't care about oil pressure or getting overheated. Drove my wife's '08 6.2L for years with probably single digit oil pressure at idle. Finally put a pump in it at like 287k miles cuz it was making lots of lifter racket from low oil pressure.

 

[CT-BLAZER]

Basics....test the sending unit, against the specs in.a GM shop manual .

2. Check the gauge using GM testing procedures.

??? What are the GM specs for oil pressure?

If your oil pressure is below GM specs replace the pump with a hi qualify Mellins pump....+ a 5¢ O ring

 

[The Griff]

Basics....test the sending unit, against the specs in.a GM shop manual .

2. Check the gauge using GM testing procedures.

??? What are the GM specs for oil pressure?

If your oil pressure is below GM specs replace the pump with a hi qualify Mellins pump....+ a 5¢ O ring

According to GM to get warranty work, an LM7 5.3 needed to have less than 6 psi at 1000 rpm, and 18 at 2000 rpm.

So according to that this 5.3 is perfectly healthy.