Tried it all, I need help. A constant Oil pressure fight.

[Collinmcballin]

How does the oil look when you drain it?

I have never changed the oil passed 3k in the 55k miles I've owned it. Definitely still sludge hiding in there. Any recommendations on further cleaning it? Run it with deisel before next oil change?

 

[Collinmcballin]

There is a possible hail Mary here with the possibility of ALOT of sludge buildup and moving around. Id drain a 1.5 quarts of oil off and then add 2 quarts of engine flush and let it idle in the driveway for 30-45mins. DO NOT DRIVE IT OR GET MUCH OFF IDLE with the flush in the oil. Then do a oil change with new filter and see if anything improves and stays improved.
If no improvement then Id be checking the couch for quarters and dollar bills....better find someone that knows someone that works at the local engine shop and shop around for beer on sale!

Man I'm almost sure it's a sludge issue...!!

 

[Collinmcballin]

Hopefully not cam bearings but likely if the truck was run for a long time with the cracked heads. When I had to replace my Castechs, it took a 4-5 short OCI's to get all the crap out even with MMO in each. After about 4-500 miles, the idle oil pressure would drop to about 20 per the cluster. What I think was happening was there were still remnants of coolant that would cause the filter to not flow as well. Current oil is about 1000 miles now and while pressure is not as high as I would like after extended highway drives it isn't as bad as before. I feel like my bearings may still be suspect as it used to idle over 40 psi no matter but I'm just gonna drive it until it grenades while acquiring a 6.0 to rebuild for later.

That's about the same boat I'm in. Did the heads over Christmas/new year, and have done 5 oil changes since. Pressure is still not predictable. I'm gonna try a thorough engine flush like @rockola1971 mentioned...ill do that the same time I install the cooler next week.
As of today it's doing great!

 

[Collinmcballin]

Relief valve plug came in today. Got the old one out with a bolt extractor I found in the drawer.
By the looks of this and the oil filter housing area... I think there's definitely still slugde hanging out in the engine.
Bypass/releif valve appears to got me 3-5psi gain (since last photos. Hmm...
Next step engine flush when the weather clears up here.

 

[OR VietVet]

You can look in my build thread to see how much I baby mine and I will never tow anything heavier than a small single axle trailer with my buddy's Harley on it. My girl has a 1990 K2500 for towing if needed.

Thank you so much. I honestly had no idea how this would go, but it's almost like talking to a good friend. Really appreciative.
NO kidding! I was dead set on an 05, only had to check paint RPO code ahead of time to know I got the good one. Drove 8hrs to AZ and only paid 4k for it. Can't wait to tell my kids that story someday. It had Never towed, never been in the dirt, and was bone stock.
Funny how that changed ;D

 

[iamdub]

I have never changed the oil passed 3k in the 55k miles I've owned it. Definitely still sludge hiding in there. Any recommendations on further cleaning it? Run it with deisel before next oil change?

That's why I was asking. If it's really black and thick, then it's still dissolving sludge that was all inside the engine. What you got out of the pan was a lot, if not most of it. But there's still plenty stuck to all the internal surfaces. I was imagining sludge being broken loose from the surfaces by the detergents in the oil. Most of it would stay suspended in the oil, making it extra thick which would cause higher pressure. The thickened oil is even thicker when cool. Maybe some of the heavier sludge settles in the pan over night and partially blocks the pickup tube, causing slow pressure rise after startup.

Kind of a few Hail Mary stabs here.

My brother's '05 Sierra had a Castech failure. It had been losing coolant very slowly for months, if not for well over a year. It lost all oil pressure one day when a large chunk of sludge in the pan broke free and blocked the pickup screen. I pulled the engine and hand-scrubbed the guts. New high-volume oil pump, new lifters, new rockers, new push rods, all new gaskets and some used 799 heads and it's been strong ever since. I have pics if you're interested.

 

[Tonyrodz]

Not to hijack your thread, but my 05 Express van with the 4.8 sounds similar to your situation. Bought it used with 110k on it. One day it slowly started losing oil pressure, until it went to 0 psi. Took it to a mechanic who dropped the oil pan. Found a load of sludge in it.
He then pulled the front cover and oil pump.
Looked like the oil was never changed. Cleaned everything up, changed the pick up O ring and installed a HV Melling oil pump. I also occassionally had to add coolant to the overflow bottle, as it would slowly lose coolant. I think one or both of the 862 heads have a crack. I read the 862 heads, like the 706 heads are prone to cracks. Not as common as the 706 heads, but they can crack. I added some of those GM tabs to the coolant almost 2 years ago and haven't had to add coolant since. My oil pressure is again down to 0 while idling--literally 0. My check gauges light comes on. Oil pressure comes up enough while revving it, but 0 at idle. Changed the oil pressure sender twice with OEM GM units, so it isn't that. I think that sludge has broken loose and are probably blocking oil passages or even the pick up screen. Weird thing is the motor doesn't knock, tick or make any other strange noises. I just thought it was strange that we're having similar issues and they're both 05 motors. Just wanted to share my experience.

 

[rockola1971]

Not to hijack your thread, but my 05 Express van with the 4.8 sounds similar to your situation. Bought it used with 110k on it. One day it slowly started losing oil pressure, until it went to 0 psi. Took it to a mechanic who dropped the oil pan. Found a load of sludge in it.View attachment 393082
He then pulled the front cover and oil pump.View attachment 393083View attachment 393085View attachment 393084
Looked like the oil was never changed. Cleaned everything up, changed the pick up O ring and installed a HV Melling oil pump. I also occassionally had to add coolant to the overflow bottle, as it would slowly lose coolant. I think one or both of the 862 heads have a crack. I read the 862 heads, like the 706 heads are prone to cracks. Not as common as the 706 heads, but they can crack. I added some of those GM tabs to the coolant almost 2 years ago and haven't had to add coolant since. My oil pressure is again down to 0 while idling--literally 0. My check gauges light comes on. Oil pressure comes up enough while revving it, but 0 at idle. Changed the oil pressure sender twice with OEM GM units, so it isn't that. I think that sludge has broken loose and are probably blocking oil passages or even the pick up screen. Weird thing is the motor doesn't knock, tick or make any other strange noises. I just thought it was strange that we're having similar issues and they're both 05 motors. Just wanted to share my experience.

Wow! The previous owner abused that engine. Im really surprised it didnt die a miserable and eventful death. You might want flush that engine with solvent. Like 10 gallons on the first run!

Seriously I doubt there is any coming back from that abuse and the only fix is going to be atleast a partial teardown and thorough and very messy cleaning.

 

[Donal]

Relief valve plug came in today. Got the old one out with a bolt extractor I found in the drawer.
By the looks of this and the oil filter housing area... I think there's definitely still slugde hanging out in the engine.
Bypass/releif valve appears to got me 3-5psi gain (since last photos. Hmm...
Next step engine flush when the weather clears up here.

How many quarts of oil are you putting in the engine when replacing oil and filter?

 

[iamdub]

Not to hijack your thread, but my 05 Express van with the 4.8 sounds similar to your situation. Bought it used with 110k on it. One day it slowly started losing oil pressure, until it went to 0 psi. Took it to a mechanic who dropped the oil pan. Found a load of sludge in it.View attachment 393082
He then pulled the front cover and oil pump.View attachment 393083View attachment 393085View attachment 393084
Looked like the oil was never changed. Cleaned everything up, changed the pick up O ring and installed a HV Melling oil pump. I also occassionally had to add coolant to the overflow bottle, as it would slowly lose coolant. I think one or both of the 862 heads have a crack. I read the 862 heads, like the 706 heads are prone to cracks. Not as common as the 706 heads, but they can crack. I added some of those GM tabs to the coolant almost 2 years ago and haven't had to add coolant since. My oil pressure is again down to 0 while idling--literally 0. My check gauges light comes on. Oil pressure comes up enough while revving it, but 0 at idle. Changed the oil pressure sender twice with OEM GM units, so it isn't that. I think that sludge has broken loose and are probably blocking oil passages or even the pick up screen. Weird thing is the motor doesn't knock, tick or make any other strange noises. I just thought it was strange that we're having similar issues and they're both 05 motors. Just wanted to share my experience.

Well, there's no need for me to find and upload the pics I have cuz they're essentially identical to this. You and @Collinmcballin having such similar experiences leads me to believe that these need to be either opened up and cleaned out by hand or slowly cleaned out over many short-interval oil changes.

Mr. Mcballin, have you any plans to remove the engine? If not, I'd suggest using cheaper, but decent oil (even Super Tech from Walmart) and filters and maybe a little engine flush (like 1/4-1/2 the bottle) and just do a lot of frequent oil changes. Maybe change it every time the average pressures are lower. I bet that, after the first few changes, you'll find that the stronger oil pressure lasts for a longer amount of time. It should improve just as the oil you're draining would get comparatively lighter. You could snap pics and record dates, etc. to document the progress.

The idea is to slowly dissolve and remove the sludge. A harsh chemical flush can break up the sludge too aggressively and clog the filter or tiny passages in the lifters, causing more harm than good. You don't wanna over-dilute ("water down") the oil with too much lightweight liquid. This is why I'm not a fan of dumping a whole bottle of Seafoam into the crankcase. Modern oils have detergent packages to keep sludge at bay. But, that's more of a maintenance function with an engine that's already up to par. Yours needs help to get to that point so I'm thinking a light dose of a cleaner would be okay. Just keep an eye on it and change it as soon as you notice the pressures acting up again.

The flip side to all this is the time and money cost of the frequent oil and filter changes. You'd have to decide to either do it this way or pull the engine and hand-scrub it. You'd be able to re-seal it, although the only seals not fresh at this point are the rear cover and rear main. So, maybe pulling it would be excessive in your case.