LS oil pressure

[2014sierraAT]

I have a 2006 6.0. A couple weeks ago I noticed at cold idle my oil PSI was fluctuating between 20-40 lbs( not gradually fluctuating, needle basically bouncing. Everything sounded fine, gave it a little gas and it come on up to 40 lbs, which is what it has idled at since I got the truck. So either the engine has done this since I’ve had it and maybe I just never let it cold idle long enough to notice or it’s something recent. Either way, what does this mean? I would think 20 lbs would be ok at idle I just don’t know why the sporadic jumps are happening.

[e015475]

You don't say if you are using the factory oil pressure sensor, but if you are you should consider replacement. Mine started fluctuating between 20 and 40 psi then between 0 and 80 psi. Lately it just pegs at 80 psi all the time. It has been this way for the last couple of years and I'll change it the next time I have to pull the manifold off for a seal leak. It sits behind the intake at the end of the lifter valley and there's some youtube videos showing removal without the intake coming off, but I tried and gave up and am waiting for the next lean code.

[2014sierraAT]

When I first noticed it was using just a mechanical auto meter gauge, I was hoping maybe it was something to do with the gauge but a couple nights ago I was in the process of swapping to a Dakota Digital gauge cluster with the BIM module so it was pulling data from the pcm and it was reading right along with the mechanical gauge.

[davepl]

It only really take 4-7 psi to float a bearing and the general "race" guideline is 10psi per 1000 rpm, but if you're getting 20-40 warmed up that's fine in my book! I'd expect to see a little more when cold though. Unless the bypass is opening at 40.

[2014sierraAT]

Originally Posted by davepl

It only really take 4-7 psi to float a bearing and the general "race" guideline is 10psi per 1000 rpm, but if you're getting 20-40 warmed up that's fine in my book! I'd expect to see a little more when cold though. Unless the bypass is opening at 40.

Since I’ve first noticed this it seems to only happen when the truck has sat for more than a couple days at a time. I can get it warmed up bring it home and let it set for a couple hours and get in it and it will jump straight up and hold a steady 40 lbs at idle. What is the bypass supposed to open at? I’m no mechanic and don’t know a bunch about these but I’ve had a lot of Ls trucks and never noticed this before. I’m just wondering if it’s something that’s usually ok or if I need to be taking it to a shop and where to even start.

[e015475]

Sounds like the pump might be losing its prime when it sits for a long time. The only way I know for this to happen is through the oring on the pickup. Has the pan ever been off and the pickup tube oring replaced?

[2014sierraAT]

Originally Posted by e015475

Sounds like the pump might be losing its prime when it sits for a long time. The only way I know for this to happen is through the oring on the pickup. Has the pan ever been off and the pickup tube oring replaced?

I’m not sure, I’ll contact the previous owner and see if he knows. Thank you.

[72 k15]

I had this problem on my 02 sierra with a 5.3 the needle was bouncing basically. I had a Donner truck 2500hd took that cluster and put it in mine fixed it. So im thinking your oil pressure gauge is worn out. That fixed mine. I hope you just talking about the 06 truck and not a motor.

[2014sierraAT]

It’s just an 06 engine, it’s in my 1970 truck

[72 k15]

Originally Posted by 2014sierraAT

It’s just an 06 engine, it’s in my 1970 truck

Oh alright, I never actually seen a oil pump fluctuate that fast before.