Low Oil Pressure on Longer Drives

[rockola1971]

I would change out the oil filter first then if no change suspect cam, rod or main bearings out of tolerance and spewing oil pressure off once warmed. Have oil lab tested and then you will know for sure.

 

[Donal]

I have seen such fluctions and problems in older SBC engines where the engine oil pump relief valve and or the oil filter adapter relief valve in high wear and dirty engines would be stuck or sticky. Probably several u tube video on the LS oil pump relief valve and oil filter relief valve to watch. Although the presenters spend a lot of time talking and not very much doing.

 

[Jfarm]

Found that I am currently running a pf46 oil filter. As I am running the correct filter and I have changed the oil and filter several times, I am unsure that it is the cause of the issue.

I did some research on a failing oil pressure relief valve and I see some similarities in the symptoms. I am thinking that the valve occasionally gets stuck open which causes the oil pressure to stay the same when I give it gas. Furthermore, I read that the valve issue can be related to temperature. I'm guessing that as the oil heats up on the longer drive, the valve starts to stick and drop the oil pressure, and when the vehicle cools down the valve frees up again.

My thought is that due to the PVC valve failing creating some sludge in combination with the high mileage, something happened with the pressure relief valve.

I could not find any solutions to try and free it up, does anyone have any thoughts? The only solution I could find is to replace the whole oil pump.

I am unable to change the pump myself and I called my mechanic to see how much it would cost to replace. He said that he could change it for $1,100-1200. He did say that since the engine has 262,000 miles on it, he recommends swapping the engine instead of replacing the pump. I am leaning toward doing the swap at this point. Does anyone have any thoughts on anything else that can be done at this point? Thanks.

 

[rockola1971]

Found that I am currently running a pf46 oil filter. As I am running the correct filter and I have changed the oil and filter several times, I am unsure that it is the cause of the issue.

I did some research on a failing oil pressure relief valve and I see some similarities in the symptoms. I am thinking that the valve occasionally gets stuck open which causes the oil pressure to stay the same when I give it gas. Furthermore, I read that the valve issue can be related to temperature. I'm guessing that as the oil heats up on the longer drive, the valve starts to stick and drop the oil pressure, and when the vehicle cools down the valve frees up again.

My thought is that due to the PVC valve failing creating some sludge in combination with the high mileage, something happened with the pressure relief valve.

I could not find any solutions to try and free it up, does anyone have any thoughts? The only solution I could find is to replace the whole oil pump.

I am unable to change the pump myself and I called my mechanic to see how much it would cost to replace. He said that he could change it for $1,100-1200. He did say that since the engine has 262,000 miles on it, he recommends swapping the engine instead of replacing the pump. I am leaning toward doing the swap at this point. Does anyone have any thoughts on anything else that can be done at this point? Thanks.

Id dump a quart of tranny fluid into the engine. Let it idle in the driveway and run for 30mins or so. DO NOT REV IT or DRIVE IT. Then do an oil change and check to see if symptoms are still there. I would think the tranny fluid would free up a sticky relief valve. If no change then my bet is on an out of spec/damaged (cam, main or rod bearing) and in that case I would drop either a used engine in it or depending on your future vehicle plans maybe even a reman long block.

 

[Jfarm]

Id dump a quart of tranny fluid into the engine. Let it idle in the driveway and run for 30mins or so. DO NOT REV IT or DRIVE IT. Then do an oil change and check to see if symptoms are still there. I would think the tranny fluid would free up a sticky relief valve. If no change then my bet is on an out of spec/damaged (cam, main or rod bearing) and in that case I would drop either a used engine in it or depending on your future vehicle plans maybe even a reman long block.

I'll try the tranny fluid and see if it helps.

For planning purposes if the fluid doesn't help, I am thinking about what engine to drop in and would like some opinions. I have no plans for a new one right now as mine has a lot of sentimental value in addition to the market right now being extremely high for used vehicles. I would like to keep the truck for as long as possible.

I would like to get some more power but I would have to see the difference in cost between a stock 6.0 lq4 or the stock 5.3 lm7. I have also been looking at remans, more specifically the ATK reman 5.3 with 385hp.

Additionally, I am unsure how my 4l60e transmission will take the extra power. I had my transmission rebuilt a year ago but I don't believe it was beefed up, I can go back to my records to double check exactly what they did.

Any recommendations?

 

[rockola1971]

I'll try the tranny fluid and see if it helps.

For planning purposes if the fluid doesn't help, I am thinking about what engine to drop in and would like some opinions. I have no plans for a new one right now as mine has a lot of sentimental value in addition to the market right now being extremely high for used vehicles. I would like to keep the truck for as long as possible.

I would like to get some more power but I would have to see the difference in cost between a stock 6.0 lq4 or the stock 5.3 lm7. I have also been looking at remans, more specifically the ATK reman 5.3 with 385hp.

Additionally, I am unsure how my 4l60e transmission will take the extra power. I had my transmission rebuilt a year ago but I don't believe it was beefed up, I can go back to my records to double check exactly what they did.

Any recommendations?

You are not likely to find a low mileage engine for your model year range, unless someone happened to throw a reman or crate motor into it and totalled the vehicle not long after. Good luck finding a salvage yard that doesnt try to pull that one "oh yeah the engine was jsut put in there 40k ago".....Like they knew the original owner of the vehicle. NOT! Your engine is a Gen3 and 2007 model year became Gen4 and there are some computer and internal reluctor wheel diffferences as well as cam and crank sensor position differences. The 6.0L is going to cost more than a 5.3L except maybe if you get into a high milage vs low mileage cost comparison. Engine prices will vary from region to region and state to state. The cheapest that ive seen but its been awhile since ive bought is oklahoma city area and south of there. Use car-part.com to shop around and you could save alot of money if you are willing to go pick up. I bought (2) Gen3 5.3L LM7's for $500 for the pair, both running but that was around 2009. If you do by a ATK 385hp you will probably have to have your PCM tuned so there is that cost. Your stock tranny will handle 450hp. If you stick a 6.0L in there with some power adders then you will likely have to get the tranny ran through and upgrade alot. Unless you have a friend at a engine machine shop, me personally I would just stick a bone stock of what is in there reman engine and call it a day if you are just using it for family transportation and get to work.

 

[BG1988]

I took your advice and added the two extra quarts. This weekend I had to make the 2 hour drive again. This time was different and may only add to the already puzzling situation.

When I went down Saturday, there was nothing different in what happened. The oil pressure started strong at around 60psi but slowly dropped to 30psi with the lifter tick starting at 40psi. Pressure returned and the lifter tick went away after the truck cooled down later that day.

On the drive back Monday night however, I did not get any ticking. I started the drive at about 55psi and 20 minutes in it dropped to 50. For the rest of the drive, the pressure only slowly dropped to 45psi. Never got a lifter tick.

While the pressure didn't drop all the way, I could tell the oil pressure was not normal. When the pressure acts normal, the pressure will shoot up when I give it some gas. When I am on the highway doing the longer drive, the pressure stays the same even when I give it gas.

Something I will also add, this morning was cold in the low 20's. I started up the truck and only got 30psi. The pressure was jumping up and down 5 psi occasionally. I drove it around after warming it up for a few minutes and randomly the pressure goes back to the normal 45psi with no random 5psi jump in pressure.

What could be causing this? If it were the O-ring, why would the two quart test not work the first time then somewhat work the second time? Could something be in the motor blocking the oil flow and potentially be lodging and dislodging internally over the course of the drive? If so, why only when operated on the highway and not at idle? Should I consider an engine flush? If it were the oil pump, I would believe the issue would appear when the earlier tests were conducted.

Thank you again for all your help on this very odd issue.

Here's a cheap shot

maybe it's time to add an oil cooler with an aux fan if heat is the "issue" if it all ready has an oil cooler then add an AUX fan to it

maybe the oil cooler fins are rotted out this is a common issue