certified GM technician question

Any certified GM techs here?
I have a couple of very specfic questions regarding the 6.0 chev vortec and some electrical questions on a 2005 Yukon XL.

I am not certified but may be able help in answering your question and if not I can ask my certified GM tech friends

I am.

2005 Yukon XL, 2500 with 6.0.
Has 135k miles

2 questions:
1) When “cold”, oil pressure is about 40psi. Once warmed up and driven, in idle, in gear, the PSI will drop below 15. Give it a little gas and it comes up to 25psi right away. Just at warm idle, oil pressure very low.
I’ve done some research and heard this is common in the 6.0 and it could be 4 things:
a) Bad oil pump
b) Bad O-ring in pump, causing it to “leak”
c) Sludge build up and there is an engine oil treatment to run through to clean out the sludge, the sludge builds up on the pick-up screen, causing starvation.
d) Cam bearing has spun and is starting to walk out and engine needs to be torn down.
I found on the web that GM put out a TB on this and that 6psi is acceptable. Yes, 6psi.

Thoughts?

Secondly;
Engine has 135,000 miles
Gauge cluster reads 5400 gal of fuel. This is not accurate.
Gauge cluster also reads 251 hours, this is not accurate.
All three numbers conflict with each other.
I’ve seen in the car fax that it had electrical issues at 50,000 miles, which may account for the fuel consumption being off, but the 251 enging hours tells me another gauge cluster malfunction.
Besides gauge cluster malfunction (which is common in 2004 and 2005), could the three readings be of any other cause?

I’m looking at purchasing this vehichle, however prior to, I need to know these answers and if I should stay clear?
I found that gauge cluster rebuilds can be done under $200 and that doesn’t really concern me, if that is what is causing the incorrect readings.

Secondly, if indeed it is only sludge build up causing low oil pressure at idle, that doesn’t concern me. Even changing an oil pump doesn’t concern me because price is correct on the vehicle. However, tearing down to replace cam bearing is a no-deal.

Thoughts???????

If it was treated like below, I’d run away fast…

Quote….
I’d attribute it to oil weight too (sludge)…..My reasoning behind this thinking is that I don’t do maintenace on my Burb. I’ve only greased the front zerks about once every 50,000 miles, never flushed the tranny or changed fluid, and change my oil only every 10,000-15,000 miles (dino oil, not synthetic). Last tune up was 100,000 miles ago.

The cluster issues is the cluster itself. The oil issue can be a number of thi gs. 5 psi is not acceptable and there is no bulletin that will state this. First thing is to verify that the gauge is reading accurate by testing it with a mechanical gauge. If it is I would run a cleaner through. I recommend bg109. Drain the oil and fill with new oil. If this fixes it the oil pressure relief Valve in the oil pump is sticking partially and the cleaner washed it out correcting it. I would then replace the oil pump. If it is a cam bearing failure you can remove the valve covers and rockers and look for damage/ oil starvation evidence like ground pushrod ends etc. I’m leaning toward the oil pressure relief valve sticking as it is temp related and I’ve seen it alot more. Cam bearing failure is much more severe and noise will be present. It also won’t be affected by engine temp.

Quote:

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If it was treated like below, I’d run away fast…

Quote….
I’d attribute it to oil weight too (sludge)…..My reasoning behind this thinking is that I don’t do maintenace on my Burb. I’ve only greased the front zerks about once every 50,000 miles, never flushed the tranny or changed fluid, and change my oil only every 10,000-15,000 miles (dino oil, not synthetic). Last tune up was 100,000 miles ago.

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THAT is FUNNY!!!!!!
But hey! I’m running 267,000 maintenance free miles!!!!
Want to buy a used suburban? I just did oil change 2000 miles ago, so oil is new and fresh!

Loomis,
See attached. It is from Jasper Engines. Was this orginally from GM?
http://www.jasperengines.com/pdf/GM60LOilPressureTB.pdf

Just looked at the specs and for the 6.0 hot at 1000rpm is min of six psi.. I misread your post and thought you said 5psi not 15. That is normal for the 6.0. A guy I work with has the 6.0 and his is 15psi hot at idle. Sorry about that.