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

[iamdub]

Gotcha! Thanks for the input a appreciate it! What product would you recommend?

I couldn't recommend any one brand/style as I've never used them. If I had to pick, I'd likely choose one based on being safe for seals. After a quick search, Rislone and Motor Medic seem to be favorites. For this instance, I'd probably use Rislone for the duration of the OCI since it's not a flush and is designed to be ran in an engine as normal. Then, maybe use an actual flush right before the oil change.

 

[Jim b]

The sound of cam bearing scares me... Pull the block and take it somewhere? Or do it at home? *frantically Google searching in the background*
Honestly the pressure was excellent for a few months after the new pump. So weird.

Your Comment about oil pressure being fine after an oil change make me think of oil dilution. It would be worth sending a sample of the "low oil pressure oil" to a good lab like blackstone. I had a ford 2.9L V6. Did everything except cam bearings, Low oil pressure when hot (new or old oil) Did the cam bearings. Fixed! But it had low oil pressure when hot with any oil, not just "used" oil. Good Luck! Jim

 

[ScottyBoy]

I just went through pretty much this SAME scenario on my truck. Tried all sorts of things, even installed a Melling high volume pump, but to no avail. At a cold startup, I had good pressure, just over 40psi. But after just 5-8 minutes of warmup, my pressure plummeted to below 20psi, and sometimes even below 10psi. I finally concluded that I had a slipped cam bearing. I checked it several times with a manual oil pressure gauge and I consistently had as LEAST 10 to 15psi more pressure at the oil port right above the power steering pump, but lower pressure at the sensor port in the rear of the intake manifold. Right before I started experiencing this oil pressure issue, I DID sort of "hot rod" my engine a bit. Could that have caused a slipped bearing? Who knows.... I finally tucked my tail between my legs and gave in and replaced the engine. I ordered a crate engine from O'Reilly Auto parts and had a guy install it for me. Not really a shop, but he is a retired mechanic with a "shop" in his backyard. I just got it back a few weeks ago and she runs great and has good consistent oil pressure. The guy did a pretty good job replacing the engine, my ONLY complaint is that he didn't paint the block. Maybe I'm nitpicking here, but it's a BARE uncoated cast iron block that's already covered in rust. IMO he could have at least sprayed some engine paint or even some cheap black spray paint on it or something. Hell, if I had known it was completely bare, I would have went over there and painted it myself if I had to.

 

[Collinmcballin]

Your Comment about oil pressure being fine after an oil change make me think of oil dilution. It would be worth sending a sample of the "low oil pressure oil" to a good lab like blackstone. I had a ford 2.9L V6. Did everything except cam bearings, Low oil pressure when hot (new or old oil) Did the cam bearings. Fixed! But it had low oil pressure when hot with any oil, not just "used" oil. Good Luck! Jim

Thanks for the input Jim!! That's almost exactly where I'm at. I'm sure the motor is worth pulling to get some new cam bearings in there.
When I did the cam I definitely saw copper, but...

 

[Collinmcballin]

I just went through pretty much this SAME scenario on my truck. Tried all sorts of things, even installed a Melling high volume pump, but to no avail. At a cold startup, I had good pressure, just over 40psi. But after just 5-8 minutes of warmup, my pressure plummeted to below 20psi, and sometimes even below 10psi. I finally concluded that I had a slipped cam bearing. I checked it several times with a manual oil pressure gauge and I consistently had as LEAST 10 to 15psi more pressure at the oil port right above the power steering pump, but lower pressure at the sensor port in the rear of the intake manifold. Right before I started experiencing this oil pressure issue, I DID sort of "hot rod" my engine a bit. Could that have caused a slipped bearing? Who knows.... I finally tucked my tail between my legs and gave in and replaced the engine. I ordered a crate engine from O'Reilly Auto parts and had a guy install it for me. Not really a shop, but he is a retired mechanic with a "shop" in his backyard. I just got it back a few weeks ago and she runs great and has good consistent oil pressure. The guy did a pretty good job replacing the engine, my ONLY complaint is that he didn't paint the block. Maybe I'm nitpicking here, but it's a BARE uncoated cast iron block that's already covered in rust. IMO he could have at least sprayed some engine paint or even some cheap black spray paint on it or something. Hell, if I had known it was completely bare, I would have went over there and painted it myself if I had to.

Thanks for the input!! I really appreciate all the replies. This is definitely helping narrow down the issue to attack the solution. Glad the truck is running good! Good thing you have a hood to cover the unpainted block, ha!

 

[Collinmcballin]

After 250k miles the motor is probably just a little tired. You may make your life easier by going and getting a junkyard either 5.3 or 6.0 and building it on a stand in your garage. Then when you're ready to go, you can swap your current, mostly fresh heads onto the motor and swap it out in a weekend.

Then you can sell the old one as a core or build it and keep it as a spare.

If I get a motor I'm definitely going this route! Thank you!

 

[03yukXL]

Have you considered running 10-40 or 20-50 in your motor? If the tolerances have widened this may quiet down the motor a bit and give it a bit more buffer. I get that it calls for 5/30 from factory, but that was a trip to the moon ago and things are different inside that motor at this point...

 

[Bill Barnes]

When I read thru the initial post I immediately thought bearings. @rockola1971 and @swathdiver beat me to it by a day. I really think you will find the problem(s) when it is torn down and gone thru. I have also, over the years heard of lower end oil pressure problems after the upper end is done and that seems to create extra pressure on the many more miles lower end. Do the barbell while apart and as I have seen with your list, continue to use quality parts and if is beyond your expertise, have a very qualified tech/shop/machinist do it right.

By the way, welcome to the forum.

Another by the way. There is just something about these 05's huh!

OR VietVet,
There IS something about these '05s! My '05 Yukon XL LT 5.3 Z-code (Flex fuel), bought new, has 231K miles on it. Now, (crossing my fingers), I have not had any oil pressure issues at all. It has 45-47 PSI at startup, and never drops below 25 PSI. I have the oil changed when the Oil Minder tells me I have 10% Oil Life remaining. I use a Valvoline Instant Oil Change center (since day one) and have always used the synthetic blend. I stay in the vehicle, and I can hear the techs communicating with each other. They triple-check every step of the way. Maybe I'm just lucky, but I sure am glad either way.
I used to do all of my own work, but at 70 years of age, I just can't any longer.

 

[OR VietVet]

OR VietVet,
There IS something about these '05s! My '05 Yukon XL LT 5.3 Z-code (Flex fuel), bought new, has 231K miles on it. Now, (crossing my fingers), I have not had any oil pressure issues at all. It has 45-47 PSI at startup, and never drops below 25 PSI. I have the oil changed when the Oil Minder tells me I have 10% Oil Life remaining. I use a Valvoline Instant Oil Change center (since day one) and have always used the synthetic blend. I stay in the vehicle, and I can hear the techs communicating with each other. They triple-check every step of the way. Maybe I'm just lucky, but I sure am glad either way.
I used to do all of my own work, but at 70 years of age, I just can't any longer.

I just turned 70 last Christmas Eve. I still like the work but am just not as fast as I used to be. I have a friend with a shop and lifts who lets me in ever now and then. He was involved in my build thread. If is more than I feel like tackling, I just hand him the keys. I do know my limitations. And yes, at 156k miles, I have great oil pressure of 45-50 at cold start and idles about 38-41 and climbs like I want it to when accelerating, hard or normal accel.

 

[AngryFish]

From what I read, it sounds like you think you need bearings and a lot of engine work, and are toying with the level of engine replacement or major machining. If you suspect a major sludge issue, a small amount of solvents added just sounds like a surefire way to be stranded somewhere when a large chunk inevitably breaks free.

The BG super mega ultra engine flush kit thingy, if you are comfortable with it, will probably be the best. It removes the sludge by dissolving it and then completely replacing the filter at each stage (as you know).
I've not used it but my engine isn't *that* dirty. I might because previously using solvent additives didn't help, but I don't have sludge issues or oil pressure issues... it would be preventative for me. I have no skin in this game.

Put it this way: you may be at the point where you need to do something drastic anyways, so this will either fix the issue or show the problem right away. Just monitor the oil pressure during the flush in case there is a sudden drop, because that could actually cause major harm if the sludge blocks the pickup.


Point is, it's cheaper than machining an engine, and you said it usually takes a bit before the oil pressure becomes a problem after an oil change. Then if you replace cam bearings anyways, you know they'll be good for a while.


I don't work in the automotive sector, but in a bandaid vs bite-the-bullet scenario, I generally don't recommend prolonging the issue if you can find the problem or solve it by trying. If it were my daily driver, my choice would be the full flush at this point. I can beg, borrow, steal (ymmv) a ride for a few days to work or get a rental car while major work is done, which would have to happen anyways if the engine goes to a shop. Or it fixes the issue.


I'm not anybody you know, so grain of salt and all that. I'm just a dude on the internet.

 

[Collinmcballin]

Have you considered running 10-40 or 20-50 in your motor? If the tolerances have widened this may quiet down the motor a bit and give it a bit more buffer. I get that it calls for 5/30 from factory, but that was a trip to the moon ago and things are different inside that motor at this point...

Yep, I think on page 1 I mentioned I've been running 10-40 for a while... Seems to be the same results

 

[Collinmcballin]

Another update!
So far so good. Still hanging on a minimum of 38psi....nice!

For some reason; recently she dumps oil, baaaad. Replaced cam sensor and crank sensor o-rings a month ago... Got worse since... It's just dumping oil out/up/around bellhousing, starter, oil filter and sheeeeesh.... Everywhere.
The underside of my truck is absolutely spackled, exhaust, trans, even my Thule bike rack is polka dotted. Freaking mess
What can even cause it to leak this bad? Anytime heat/ac is on it smells like my 97 cr250 2 stoke... LOL
I'm tempted to yank the motor now. It's so annoying. throw cam bearings in like ya'll mentioned, and be done with this thing already.

 

[OR VietVet]

Oil pressure sensor puking or back of intake puking? Check the oil filter adaptor too.

 

[AngryFish]

What can even cause it to leak this bad?

Well, the good news is that you'll find it if you pull the motor, so you may want to get parts ready. if you know the valley plate and intake and such are good, it's very probably the same issue I just had repaired at just shy of 300k.

On the back of the engine block, there is a cover that holds the rear main seal. The top of this cover also has an oil gallery that moves oil from the left to the right side of the block (for the heads, I think...). The cover has a rubbery elastomer seal that likes to go bad and cook, and when that fails it will spray oil. And it coats everything underneath... I had that issue for sure and thought my rear diff was leaking again at first. Usually cooks after about 150,000 miles, and it's on borrowed time after that causing a minor coating of oil that looks like it's from the oil filter adapter but isn't.

So good news, it's not the rear main. The bad news is that it might as well be.

Another option is leaks from the valley cover plate being loose, so you can check that, but probably not a common issue. It was loose on my truck, but I also was puking oil from the rear main cover plate. The valley plate was a gentle seep by comparison.

 

[AngryFish]

For reference, the rear cover is part #28 and the seal in question is #29. Rear main seal itself is #27. Usually available from GM as a kit with 27, 28, and 29. I don't have a number though...

 

[Collinmcballin]

Just checking in here again. Engine is still leaking worse than ever. Qt a week. Under the truck is soaked. Still runs like a champ of course. My pops talked with a few guys when he was picking up an engine last weekend. They said the motor is tired and ready for a new one. Ehh...
Oil pressure has still been spectacular for a FEW months now. It just doesn't like off roading it seems. Next plan is to install that oil cooler right behind the removable bumper valance air ducts.
Also starting an engine swap on my mom's Yukon this weekend.
Seems as my oil pressure dilemma is still hibernating...

 

[Collinmcballin]

update... sorry to be gone, i got married and been a busy year haha!
5k away from 300k. truck runs like a champ but engine is getting tired. oil pressure has NOT been phased in a couple years now. seriously what a relief!
trans finally gave up 2nd gear last november, saving for a built FLT 4l60e for a couple months now. hopefully july will have $ saved driving it mellow-ish for now

FULL FIX as below
-Melling m295 pump, shimmed pump spring with 2 washers, & fresh pickup o-ring
-melling cam retainer plate (this one was a MAJOR fix)
-de-sludge, scrape oil pan when doing the pickup tube. plus multiple (5) ~500-800 oil changes (but now it leaks so bad its always new oil lol)
-sprayed out push rod oil holes with brake clean why not

within the time of not posting- i have done the same tactic to 3 other 200k+ gmt800's with the same success

LQ9 swap is next, these trucks are so good & worth keeping
cheers