Another Oil Pressure Quandary

[Marky Dissod]

Reduced Engine Power ...

Remember this being called Limp Home Mode, which was when the transmission picked one gear and stuck with it; a manual shift into 2nd was possible sometimes.
Now with the electronic signal throttle, it can cover for the engine or the transmission, I guess.

 

[Joseph Garcia]

As to his earlier comment about oil pressure increasing once it's warmed up..... While you have the pan off, you might want to take a look at your oil pressure relief valve in the oil pump. Little bits of carbon and whatnot make it stick. Wouldn't be a bad idea just to replace the oil pump itself . (In addition to the aforementioned o-ring, two bolt girdle for the pickup tube, and that pressure relief valve mounted in the oil pan)

Yep, I suggested those in comment #4.

 

[SweetNubbinz]

Thanks for all the input. I'll do the valve cover for now. As we get colder I'll watch things. If the pressure gets worse I guess I'll try the 2 extra quarts thing and maybe try to find someone do do the recommended fixes. I can't see myself doing them all with my knee the way it is right now. I think i could pull off the pick up tube but not the oil pump. Honestly, it's the low at cold and normal at warm thing that's made this so hard.

 

[SpareParts]

You can do the oil pump and O ring without taking off the pan. I have done it twice now on different GM's
Check out post #60 https://www.tahoeyukonforum.com/thr...ple-problems-today.151052/page-3#post-1923000

 

[hagar]

In my winter truck (2008 sierra 5.3) I had the same problem. It was the oil pressure sensor screen partially plugged up. It would show low oil pressure when cold because the viscosity of the oil is higher when its cold. Once it was warmed up, the oil thinned out and was able to make it past the restricted screen, and show higher oil pressure. The colder it got, the worse it got. If it was a summer day, it was normal, if it was near freezing, it would go halfway to normal on cold start, and when it was minus 30, it would show no oil pressure and ding away until the truck got some temp into it.

 

[ratman90]

Hey folks,

2008 Chevy Tahoe, 5.3L, 177K miles

History of the issue: a few months ago I was coming back from a longer drive (approx 150 miles) and as i exited the freeway my oil dived to near nothing and I received warnings, don't remember the exact wording. I immediately pulled over and shut down and checked the oil. Found it was about a quart low, barely on the stick. I started it back up and things were fine so I started back home. About half way it dropped again but feathering the gas brought it up. I powered through the last half mile that way. I filed the oil when I got home and found the oil pressure lower than usual but steady. I dropped it off at my local mechanic and they wanted to replace the oil pressure sensor. I was doubtful because I had replaced it the year prior when it quit reading altogether. They replaced it and said all was good but my oil was still low. I know my oil was always around 40 at idle and would increase with the throttle as is expected. Following this incident and the repair, it was 20 and would raise a bit with the throttle. The shop says it was within spec. I went home and changed the oil and filter. I have used Royal Purple HMX and WIX filters since I bought the truck with 132K on it. Immediately everything looked good so I figured I just paid $700 for an oil change I did myself. Lesson learned.

So about a month ago, the low oil pressure started again. But I noticed that it was only when cold. After the engine is up to temp, it's back to 40+. This seems opposite of what i would expect. I was under the impression that thicker oil would cause HIGHER pressure then it should lower as it heats up. I changed the oil again at about mid-change interval. No change. What is going on here? Oil pump? Pick up o-ring?

Wish I knew a good mechanic I could trust.

Just had the same as you and about the oil pressure sensor and socket and all that had not put it in yet. 2002 Chevy 6 l 2500 HD.

208,000 mi I've taken great care of it since I got it $160,000 mi.
Oil pressure dropped while I was in Oklahoma during a gun conference heard no tickety-tacity talked to my mechanic Don't hear any engine noise he said yeah it's just that damn sensor.

5 hours later I blew the engine in Hays Kansas 5 hours from Colorado.
$9,000 later remanufactured engine and all the good accoutrements.

Still cheaper than trying to buy another truck to replace it with unknown problems.

My only thought is if there's another place for you to put another external oil sensor and see what another gauge would give you. Cuz you may have oil pump o-ring issue or failing oil pump like I did.

 

[j91z28d1]

yes. there's a port on the side on the block right after the oil pump you can put a gauge on. it's the same thread as the back in the intake. there's also a remote mount sensor hose you can buy. then keep a known good one with you on the road.

 

[j91z28d1]

this was the o ring that came out of my 170k 2011 a month or so back. still mint, still soft. bearly even a shape to it.


I didn't use the o ring that cam with the new oil pan gasket. since mine has a bit of a odd oil pump, I went to the parts department. ended up being the same part number as normal, but I did see on the screen they called it a Teflon coated o ring. I don't know if some point gm upgrade the o ring or what. but I only changed it cause I was in there, definitely no loss of pressure from it.

 

[ZKWBQD]

Hey folks,

2008 Chevy Tahoe, 5.3L, 177K miles

History of the issue: a few months ago I was coming back from a longer drive (approx 150 miles) and as i exited the freeway my oil dived to near nothing and I received warnings, don't remember the exact wording. I immediately pulled over and shut down and checked the oil. Found it was about a quart low, barely on the stick. I started it back up and things were fine so I started back home. About half way it dropped again but feathering the gas brought it up. I powered through the last half mile that way. I filed the oil when I got home and found the oil pressure lower than usual but steady. I dropped it off at my local mechanic and they wanted to replace the oil pressure sensor. I was doubtful because I had replaced it the year prior when it quit reading altogether. They replaced it and said all was good but my oil was still low. I know my oil was always around 40 at idle and would increase with the throttle as is expected. Following this incident and the repair, it was 20 and would raise a bit with the throttle. The shop says it was within spec. I went home and changed the oil and filter. I have used Royal Purple HMX and WIX filters since I bought the truck with 132K on it. Immediately everything looked good so I figured I just paid $700 for an oil change I did myself. Lesson learned.

So about a month ago, the low oil pressure started again. But I noticed that it was only when cold. After the engine is up to temp, it's back to 40+. This seems opposite of what i would expect. I was under the impression that thicker oil would cause HIGHER pressure then it should lower as it heats up. I changed the oil again at about mid-change interval. No change. What is going on here? Oil pump? Pick up o-ring?

Wish I knew a good mechanic I could trust.

I HAD that problem until I stop using the sewing machine oil that GM recommended. Now that I'm using 5W-30 my oil pressure always is good. The old EPA prevented dealers from using something different. That restriction is now gone. You're free to choose your own oil weight now.

 

[j91z28d1]

I HAD that problem until I stop using the sewing machine oil that GM recommended. Now that I'm using 5W-30 my oil pressure always is good. The old EPA prevented dealers from using something different. That restriction is now gone. You're free to choose your own oil weight now.

you might have a newer truck. this is for 07-14. they have always recommend 5w30. and op is running 10w40 with only a few psi different.


if you have a newer one that calls for 0w20. God have Mercy on your wallet when those new Di LT engines get into the high 200 to 300k range. I don't know what's less reliable, the Di gm engines for the 8&10 speed tranny.

 

[Tom-M]

I had this same exact problem with my 2008 Trailblazer with the 5.3L engine. There is a screen under the sending unit near the back of the intake manifold. I removed the sending unit, pulled out the screen, replaced the sending unit with a new one and it never did it again.

 

[mikez71]

I had this same exact problem with my 2008 Trailblazer with the 5.3L engine. There is a screen under the sending unit near the back of the intake manifold. I removed the sending unit, pulled out the screen, replaced the sending unit with a new one and it never did it again.

So that's 2 with the same symptoms. Tom-M and Hagar.
Hagar's explanation is the only one I've heard for low pressure cold and high pressure hot?