Dragging my feet to throw parts at it, oil pump? Relief valve?

[NateDiggity]

So I have some on going low oil pressure on my wifes 07 Yukon denali 6.2. We bought it with what turned out to be a faulty pressure sensor and now Im trying to make the best of it.

I have replace the sender, and know about the screen under it.
I have also done a seafoam engine flush (hey, it couldnt hurt right??) and actually gained about 2.5 PSI all around at Hot idle (I am keeping that in mind)
I changed oil after sender to AC delco filter and synthetic, after having more issues I did the seafoam flush, and changed back to dino oil and AC filter (I figure if I am draining it in a week or two to do oil pump I may as well)

What I am trying to figure out is this, the oil pumps dont really "go bad" its just the bypass right? I realize they are not really repairable so thats why you need to do the entire pump. I also plan on doing the o ring when in there if I decide I think its the pump...

Here are my pressures, sorry about the jumbled up gauge layout, it was done on the fly:


Low temp, after start up, with a "warm up" idle speed of over 700 rpm:


Warmer still, at idle:


Hot idle, and lower RPM:


And going down the road at normal operating temp:



Does this seem like the pump or bypass? When cold or at RPM it seems to pump decent, at first start up the pressure is 50+ and creeps down...

If the o-ring was toast it would be low pressure all the time correct, same with the relief valve? Unless when its thicked (cold) it doesnt blow past it, and only after thinning out...

Either way I am probably dropping the pan, I seem to have a pan leak so I plan on starting there, dropping and fixing, replacing o ring from underneath and starting and see how it idles (With front diff lowered, xmember out etc). If that still doesnt solve the issue, then I plan on taking timing cover off and replacing pump (and I will drop the pan again since I will be right there to make my life easier).... So should I just order ALL the parts on need, then return the pump if I replace o ring and it works? Just looking for thoughts and suggestions

No engine noise, no metal in oil in both changes, hoping for it not being cam bearings....

 

[02Lightning]

If I were doing it, I would run it for 1000 miles and then send the oil off to http://www.blackstone-labs.com/free-test-kits.php and see what they say. Then if all is good with the oil, replace the o-ring and pump at once if I was going to all that trouble. Maybe email blackstone-labs and ask how long you would have to run the oil to get a good sample, maybe you won't have to go 1000 miles.

 

[02Lightning]

First thing is first, I know replaced the sender, but I would put a mechanical gauge on it to verify?

 

[NateDiggity]

I have not done a mechanical gauge to verify, I believe the sender port is some odd ball size threads from what I have read.. still trying to track one down that will work

 

[02Lightning]

This may not help you but, I think they make kits that will screw in-between the filter and block to check pressure with a mechanical gauge.

 

[NateDiggity]

So I don't have it all back together yet to verify but I only dropped pan at this point....


And






How did I have any oil pressure at all? What you can't see is the o ring is super flat and brittle, when I took it off I broke it into pieces supppper easy...

 

[02Lightning]

Awesome! It's always good to find the problem. Are you putting on a new oil pump along with the o-ring?

 

[NateDiggity]

At this point, no. I dropped the pan to replace the gasket, because it was leaking and decided to look at the O-ring first. I will see what this does and go from there.

 

[WBH05]

Good find....I just did the same thing and then some on my new to me 05 6.0. On a different note can you possibly give me the PID info for oil pressure in your torque app? Did you have to enter it manually? I cannot for the life of me find it in my app and have used torque ever since it came out years ago on diesel trucks.

 

[NateDiggity]

I'm super new to torque but where I found it was

Settings-manage extra PID and selected the preloaded list that includes GM. Then manually enabled it and oil temp from there..