Low Oil Pressure on Longer Drives

[Jfarm]

Hello all, I am having issues regarding my 2001 Tahoe 5.3L 260,000 miles. I first started having issues a month ago when I took the truck on a two hour drive. At the start of the drive, I had perfect oil pressure at 65psi driving around 75mph, but about 20 minutes in the pressure dropped very slowly. About an hour in, the pressure reached 40psi then I started getting a lifter tick. The pressure eventually got down to 10-15psi and would bounce occasionally from 5-20psi. The next morning, I started the truck and the lifter tick was still there and the oil pressure was sitting around 35-40psi. After about two minutes of driving around town about 35mph the lifter tick went away and the pressure eventually returned to normal. I decided to change the oil to see if anything was wrong. When we pulled the filter, there was some black sludge at the bottom. This was very surprising as I am very good about changing the oil on time and have never had any issues. I took it to my mechanic and he found the pcv valve was not working properly and believed that caused the sludge and ultimately low oil pressure. When I took the truck on another 2 hour trip the same pressure problem occurred and went away in the morning after driving for a bit. I changed the oil before bringing it back to the mechanic and there was sludge at the bottom of the filter again. When I brought it back to the mechanic, he changed the oil pressure sensor connector as it was "loose" and he thought it might be causing the sludge. When I took it for another 2 hour drive the same issue occurred. I took it to the mechanic for the third time he said he's not sure what's wrong and believes that it could be caused by the oil pump starting to get tired at 260k. When I drive around town the pressure is absolutely fine, the problem only occurs when I take it on longer drives. While I may not have much experience with these issues, I find it hard to believe that the oil pump is starting to go when I get perfect oil pressure on shorter trips where it even gets up to 75 psi. I have changed my oil 6 times (5w30 conventional) in an attempt to flush out anything that might be causing the pressure issues but in the three times since the pressure connector was changed I do not see any sludge. Two things I want to add that might be helpful is that in the morning when I start the vehicle, the pressure sits around 40psi but as everything warms up the pressure returns to around 60psi. Additionally, on one of the longer drives, I stopped at a gas station after I got low oil pressure and ticking. When I started the truck after filling up, the ticking and pressure went away only to return 15 minutes down the road. Does anyone have any thoughts on what could be the issue?

 

[corvette744]

Sounds like a couple things but i would take the oil pan off first-check for sludge in the bottom of the pan and pickup screen on oil pump.I would assume you have alot in the engine.Getting down to 5 psi and engine ticking might be causing alot of damage on the bearings and piston shirts.Having that much sludge choking up a filter you might have to take off valve covers pan hell even front timing chain cover to get everything clean good luck.

 

[rockola1971]

During all those oil changes I would have ran engine flush through the oiling system since you know there is sludge in the engine.

 

[swathdiver]

Hello all, I am having issues regarding my 2001 Tahoe 5.3L 260,000 miles. I first started having issues a month ago when I took the truck on a two hour drive. At the start of the drive, I had perfect oil pressure at 65psi driving around 75mph, but about 20 minutes in the pressure dropped very slowly. About an hour in, the pressure reached 40psi then I started getting a lifter tick. The pressure eventually got down to 10-15psi and would bounce occasionally from 5-20psi. The next morning, I started the truck and the lifter tick was still there and the oil pressure was sitting around 35-40psi. After about two minutes of driving around town about 35mph the lifter tick went away and the pressure eventually returned to normal. I decided to change the oil to see if anything was wrong. When we pulled the filter, there was some black sludge at the bottom. This was very surprising as I am very good about changing the oil on time and have never had any issues. I took it to my mechanic and he found the pcv valve was not working properly and believed that caused the sludge and ultimately low oil pressure. When I took the truck on another 2 hour trip the same pressure problem occurred and went away in the morning after driving for a bit. I changed the oil before bringing it back to the mechanic and there was sludge at the bottom of the filter again. When I brought it back to the mechanic, he changed the oil pressure sensor connector as it was "loose" and he thought it might be causing the sludge. When I took it for another 2 hour drive the same issue occurred. I took it to the mechanic for the third time he said he's not sure what's wrong and believes that it could be caused by the oil pump starting to get tired at 260k. When I drive around town the pressure is absolutely fine, the problem only occurs when I take it on longer drives. While I may not have much experience with these issues, I find it hard to believe that the oil pump is starting to go when I get perfect oil pressure on shorter trips where it even gets up to 75 psi. I have changed my oil 6 times (5w30 conventional) in an attempt to flush out anything that might be causing the pressure issues but in the three times since the pressure connector was changed I do not see any sludge. Two things I want to add that might be helpful is that in the morning when I start the vehicle, the pressure sits around 40psi but as everything warms up the pressure returns to around 60psi. Additionally, on one of the longer drives, I stopped at a gas station after I got low oil pressure and ticking. When I started the truck after filling up, the ticking and pressure went away only to return 15 minutes down the road. Does anyone have any thoughts on what could be the issue?

I read this as an o-ring issue with the oil pump's pick up tube. Toss another 2 quarts in there on the next trip and see if it goes away, the additional oil submerges the o-ring.

 

[Jfarm]

All, appreciate the input. I forgot to mention that I did put an oil additive in during my second oil change. With all this being said, I believe it may be inevitable and I have to drop the oil pan to check for sludge, bad o-ring, etc... However, if I drop the oil pan, should I just replace the oil pump while I am down there? Is there anything else that I should look at while I'm in there?

 

[corvette744]

All, appreciate the input. I forgot to mention that I did put an oil additive in during my second oil change. With all this being said, I believe it may be inevitable and I have to drop the oil pan to check for sludge, bad o-ring, etc... However, if I drop the oil pan, should I just replace the oil pump while I am down there? Is there anything else that I should look at while I'm in there?

If you take the pan down you will now by the amount of sludge it has in it if you need to tear down any more of the engine.If it all looks clean i would replace oil pump and screen and o ring with 260k and your already in it i would do the pump.Im thinking you have alot of sludge down in it but maybe not.Like people say you could run some engine cleaner in it or sea foam in the oil before you drop the pan for inspection.Also makes no sense how your oil pressure is at 40 when cold and when warm goes up to 60psi or more should be the opposite.Mine is 40 psi almost always and when im full throttle of the line will jump to 60 maybe until i let off the gas.An engine ticking is the kiss of death-your push rods could be getting choked full of sludge also-all of that is no good.

 

[Jfarm]

If you take the pan down you will now by the amount of sludge it has in it if you need to tear down any more of the engine.If it all looks clean i would replace oil pump and screen and o ring with 260k and your already in it i would do the pump.Im thinking you have alot of sludge down in it but maybe not.Like people say you could run some engine cleaner in it or sea foam in the oil before you drop the pan for inspection.Also makes no sense how your oil pressure is at 40 when cold and when warm goes up to 60psi or more should be the opposite.Mine is 40 psi almost always and when im full throttle of the line will jump to 60 maybe until i let off the gas.An engine ticking is the kiss of death-your push rods could be getting choked full of sludge also-all of that is no good.

I agree it makes no sense haha. The only ticking I get is when I drive for about an hour but then it goes away the next morning after sitting. If it isn't the o-ring, the thought I have is that when I drive a while it slowly picks up sludge from the pan and slowly clogs stuff up and when I stop the engine it drops what sludge might be picked up. Just a theory as I'm stumped. I may use a snake camera and put it down the dipstick tube to check the pan before I pull it just to set expectations. Most likely I'm going to need to pull the pan soon and replace the pump, screen, and o-ring. I'll probably have time Friday to check the pan with the camera. Thank you for the help and I'll update when I find out what's down there with the camera.

 

[swathdiver]

All, appreciate the input. I forgot to mention that I did put an oil additive in during my second oil change. With all this being said, I believe it may be inevitable and I have to drop the oil pan to check for sludge, bad o-ring, etc... However, if I drop the oil pan, should I just replace the oil pump while I am down there? Is there anything else that I should look at while I'm in there?

No, I wouldn't touch the pump, just the o-ring. It makes good pressure. I've seen too many guys on these forums lately with oil pump problems.

 

[Bill 1960]

Paragraphs!

Can you be more explicit on “changing the oil on time”; is that by the OLM, 10k, 5k, or what? Reason I ask is it has a big input in sludge formation.

I would do the easy diagnostic test as suggested by @swathdiver because at that age and mileage the O-ring is highly suspect.

2wd or 4wd? That has a large impact on how big a deal dropping the pan is.

 

[Jfarm]

No, I wouldn't touch the pump, just the o-ring. It makes good pressure. I've seen too many guys on these forums lately with oil pump problems.

Interesting. You do have a point, it does make good pressure. Hopefully when I get down there I see the o-ring has worn or a sign pointing to anything but the pump. Would rather not replace the pump if I don't have to.