Oil pressure oddity

[Tahoehybrid18]

08 Tahoe Hybrid. Was drinking last weekend when oil pressure slowly went down to zero while driving. Read the forums, seen the sensors are suspect, so I replaced it and the screen. Drive good for about a week, now tonight it did the same thing. Pressure started out good, then slowly crept down to zero over 2 to 3 mins. I got home, turned it off for 15 seconds, started backup and pressure was steady around 40 at idle. What gives, seems pretty odd. Oils full, was changed about 1500 miles ago.

 

[Derick]

Well you fixed 1 of the 3 issues...

1) sensor
2) oil pickup tube o ring
3) oil pump check valve

I'd go for marvel mystery oil ASAP to see if you can perhaps free up that check valve in the pump. Either way, depending on mileage, plan to replace the pump. The high pressure/high flow aftermarket pumps are 150+30 for a new pickup tube.

 

[SnowDrifter]

Those have a screen too that clogs

 

[Derick]

Those have a screen too that clogs

He said he replaced the screen.

 

[Tahoehybrid18]

Yes screen replaced, now the first time I had to drive 10 blocks home, with the gauge at zero. When I got home, engine was quiet, no lifter tick or anything. Is it possible that this is a electrical issue? I find it hard to believe the pump is bad or this valve just randomly messes up after the engine gets warm. I'm fairly knowledgeable as I have built SBC engines for circle track racing.

 

[swathdiver]

Yes screen replaced, now the first time I had to drive 10 blocks home, with the gauge at zero. When I got home, engine was quiet, no lifter tick or anything. Is it possible that this is a electrical issue? I find it hard to believe the pump is bad or this valve just randomly messes up after the engine gets warm. I'm fairly knowledgeable as I have built SBC engines for circle track racing.

Did you plug it back in? LOL Did you replace with GM OE or ACDelco Professional?

 

[Tahoehybrid18]

Yes I plugged it in, and yes it was a AC Delco

 

[SnowDrifter]

At this point, I'd say hook up a mechanical gauge. Separate mechanical from electrical and proceed with diagnostics from there

It doesn't escape me that it's an annoying thing to hook up given where the pressure sensor is. But it's gotta be done. If your oil pressure is truly low, it'll stop you from blowing up a couple thousand dollar engine. And if it's not, you can avoid chasing your tail and throwing un-needed parts at the thing

 

[Tahoehybrid18]

I'm going to have a dealership diagnose it for me, it's hard with Wisconsin winter right now to do much on my own lol

 

[dnt1010]

Hopefully something simple. Not that many Hybrid 6.0s around so it catches my attention when I see someone post a problem with one.
On your 2008
1. How many miles on it and is this the original factory engine?
2. Have you added anything to the latest oil change that might have loosened internal oil sludge deposits? (Kreen etc)
3. In the past say 1 year what pressures were you normally seeing on the dash guage. Usually pretty high on cold startup? and then a lower number at idle after completely warmed up?
4. Any other dash gauges or center screen controls acting different lately?

 

[Tahoehybrid18]

I just bought it in November, it has 160k miles on it, it adds appears to be the original engine. I got a full Carfax history with it, I am the 3rd owner. However, in between the first and second owner it was returned under lemon laws, and is classified as a lemon. But the 2nd owner had it 8 years and no major work was done to it. Oil pressure had never been a issue. It was always around 60 at cold startup, and even this morning it was still 60 at start up. But as the engine and oil warns it just drops slowly to nothing. Only thing that stood out, was a month ago I took it it on a 1.5 hr drive, and it kinda did the same thing, but once I got off the interstate it shot back up and was fine. The dealership did a oil change but i have no clue what oil or filter they used.

 

[KVacek]

Might not be your issue, but we had an oil weirdness on our 93 Suburban. Even a slight overfill of the oil would cause foaming and that would indeed reduce oil pressure.

I almost always do all my own work on all my vehicles, but once when it was nasty cold (Chicago area) and there was a GM dealership offering a $25 oil change and wash, I took the bait.

Long story, but apparently the genius did a double oil fill with their fancy automatic oil fill system.

Next time was a year later on a trip when we had an oil change out of town and they apparently overfilled it a bit. Not containers - a pump into an oil fill can - so who knows. On the way home, at high speeds (maybe 80+ ?) the oil pressure would fluctuate a bit and if I'd stop quickly and check the stick there'd be foam. Stayed below that speed and it was OK, and once we got back home I changed it again and it was fine thereafter.

From then on I always made sure the level was never above the FULL mark. Any change i did on that truck, I used 5 quarts and it never happened. But let a "professional" touch it and there was a very good chance of an issue. Ran it many years more, eventually getting rid of it at 276,000 miles. Still good oil pressure.

 

[Tahoehybrid18]

Ok. So dealership had it, checked it over. They believe it's a bad / inferior oil filter. The dealership I bought it from was a Lexus dealership and I have a feeling they went cheap. They are thinking because the oil pressure starts good and slowly drops after quite a long time at idle, and the fact that it comes back to great pressure if you kill the engine, wait 5 seconds and restart. They will change oil tomorrow and we shall see.

 

[swathdiver]

I almost always do all my own work on all my vehicles, but once when it was nasty cold (Chicago area) and there was a GM dealership offering a $25 oil change and wash, I took the bait.

Long story, but apparently the genius did a double oil fill with their fancy automatic oil fill system.

Next time was a year later on a trip when we had an oil change out of town and they apparently overfilled it a bit. Not containers - a pump into an oil fill can - so who knows.

Twice since getting married someone else has changed our oil because I was sick and my wife wanted to surprise and help me. Both times the knuckleheads over-filled the motor. I've taught my children to do it now but also to check each other's work in case mistakes are made. So after I'm done underneath, one of them will crawl under and double check the plug and filter and any oil not wiped up. Do the same thing up top too, just as we did when I ran an oil change shop decades ago.

 

[Tahoehybrid18]

This place works on our fleet vehicles, been working with them for 13 years. Hate to have someone else all in my under bridges but Wisconsin winters make things difficult lol.

 

[Wolfbraid]

Ok. So dealership had it, checked it over. They believe it's a bad / inferior oil filter. The dealership I bought it from was a Lexus dealership and I have a feeling they went cheap. They are thinking because the oil pressure starts good and slowly drops after quite a long time at idle, and the fact that it comes back to great pressure if you kill the engine, wait 5 seconds and restart. They will change oil tomorrow and we shall see.

Very possible, I don't remember what mine had when I bought it, but I put a K&N on thinking it would be better, used them before and never had problems. Second time I used a Fram XG... and now an AC Delco filter(they sell them at walmart)

so after a switch to sythetic, two engine flushes, and back to an ACDelco filter... everything seems to be just fine.

 

[swathdiver]

I put a K&N on thinking it would be better, ...back to an ACDelco filter.

Did you have any problems with the K&N oil filter and if so, what?

 

[Wolfbraid]

Did you have any problems with the K&N oil filter and if so, what?

I don't know if I did, or didn't.
I got the yukon in September, after a while I did a oil change to Mobil 1 synth and k&N... some time later after Jumping on the throttle with some exuberance, I had a "OIL pressure" light. Changed the oil sensor and oil sensor filter, did an engine flush treatment and changed the oil and oil filter(M1/FRAM.) Light went away for a while til one day it came back.. Decided to flush and change again(might have used penzoil was on sale and M1 is getting expensive/AC delco filter) All has been good for a couple thousand miles, including some spirited driving.

Now I don't know if the Synth oil caused old oil deposits to break up, I don't know if the oil filter failed to catch these, I don't know if other filters lack a good anti-drainback valve(I read that somewhere it is a concern) what I know right now, is I don't have a problem, so I'll probably stick with the A/C filter, it's cheaper.

Also do yourself a favor and spend the $4 on the oil filter wrench(the one that fits over the end like a socket) you can put on/off with a 3/8 ratchet.


As your oil pressure changes, maybe it's the oil pickup in the pan, there is a problem with the older o-ring on the pickup aging and causing pressure issues.

 

[swathdiver]

I don't know if I did, or didn't.
I got the yukon in September, after a while I did a oil change to Mobil 1 synth and k&N... some time later after Jumping on the throttle with some exuberance, I had a "OIL pressure" light. Changed the oil sensor and oil sensor filter, did an engine flush treatment and changed the oil and oil filter(M1/FRAM.) Light went away for a while til one day it came back.. Decided to flush and change again(might have used penzoil was on sale and M1 is getting expensive/AC delco filter) All has been good for a couple thousand miles, including some spirited driving.

Now I don't know if the Synth oil caused old oil deposits to break up, I don't know if the oil filter failed to catch these, I don't know if other filters lack a good anti-drainback valve(I read that somewhere it is a concern) what I know right now, is I don't have a problem, so I'll probably stick with the A/C filter, it's cheaper.

Also do yourself a favor and spend the $4 on the oil filter wrench(the one that fits over the end like a socket) you can put on/off with a 3/8 ratchet.


As your oil pressure changes, maybe it's the oil pickup in the pan, there is a problem with the older o-ring on the pickup aging and causing pressure issues.

I bought one of those sockets, the one @randeez posted but it did not fit my M1 filter. I forgot to ask him which filter it fits. I have read that Champion Labs makes the Mobil 1 and K&N filters and that when using the M1, the oil pressure is slightly lower as it is more restrictive. I haven't REALLY paid attention but I think this is right.

 

[Wolfbraid]

I bought one of those sockets, the one @randeez posted but it did not fit my M1 filter. I forgot to ask him which filter it fits. I have read that Champion Labs makes the Mobil 1 and K&N filters and that when using the M1, the oil pressure is slightly lower as it is more restrictive. I haven't REALLY paid attention but I think this is right.

I test fit the socket(on the filter i was buying) when I was at Walmart...to make sure I got the right one. otherwise i guess a strap style would work.