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

[Collinmcballin]

Hi all. Collin here. I kinda feel like a theif lurking on these forums for years. It's my time to chime in and hopefully help/and get some help. No idea how this works but gotta start somewhere.
I have a 2005 Tahoe. Great truck, awesome condition. 251k miles, trans never been touched lol. I take really good care of it and it's not hot rod'ed

I've been fighting an oil pressure dilemma for a year and a half. I've used this forum, knowledge, videos, everything. Still can't win.
Standard 5.3 lm7, just rebuilt top end after dramatic water pump failure and those stupid 706 crack-tech (castech) heads cracking.
Ported 243 heads, ls6 springs, melling cam. Pass CA Smog, no tune. That's a conversation for another time. No CEL, The engine is quite fresh, still leaks like a siv who cares. Wicked torque.
I've always tried to fix my low/dropping oil pressure. The only way to get it back up is to change the oil. Ready to hear what I've already done...? (besides heads, cam, lifters, rockers, etc. She's clean on the inside and well maintained)
-oil pan, and gasket (de-sludged it)
-oil cooler block gasket
-melling 295 pump
-pick up tube and o ring (obviously)
-PCV system re-route to avoid consumption
-crank and cam sensor o-rings (common leak)
-Cam gear, chain
-Cam retaining plate
-sending unit along with that stupid NON EXISTENT screen everyone talks about HAHA
Literally everything. Help.

*Truck loses oil pressure, especially after light off roading or going up to mountains (heat?) 10psi
*Rattles on cold/sitting a while startup and takes 10 seconds to build pressure (and up to 30sec after an oil change)
*it will hold 45psi hot/idle for the first couple days after oil change
*valvetrain rattling when the pressure goes down NOT A SENDING UNIT DON'T GIVE ME THAT JUNK
*I KNOW the truck has good oil pressure in there somewhere, it truly runs awesome when I'm not getting whipped by oil pressure dilemmas
*checked with Guage everything is accurate

I feel like I've literally done everything and I'm losing hope. So much time put into it. Such a great truck!

Adding an oil cooler next week, for preventive care
Gtx 10-30
I've had the motor basically apart and got rid of as much sludge as possible. That was last year

SHEESH that was a long one.
Thanks guys

 

[rockola1971]

Did you freshen up the block? New Cam, Rod and main bearings? Replace dog bone? Missing dog bone?

 

[Collinmcballin]

16.5avg yup.
Great vehicle

 

[Collinmcballin]

Did you freshen up the block? New Cam, Rod and main bearings? Replace dog bone? Missing dog bone?

I didn't have the motor out completely. It was basically down to long block in the hood haha. The work I've done has been over the course of last 1.5 years.
Bearings looked good. No dog bone because motor is still in.
BUT Wouldn't that result in no oil pressure at all..?

 

[swathdiver]

Have you changed brands of oil filters too?

My money is on worn bearings, cam bearings specifically.

Take a weekend on put new rings and bearings in the motor, sounds like you are young, healthy and knowledgeable enough to make this an easy peasy job!

 

[rockola1971]

I didn't have the motor out completely. It was basically down to long block in the hood haha. The work I've done has been over the course of last 1.5 years.
Bearings looked good. No dog bone because motor is still in.
BUT Wouldn't that result in no oil pressure at all..?

Not likely the dogbone (left out) since you didnt take block down to rebuild fully. I suspect cam bearings is your problem if you replaced oil pump to fix the problem and the problem still existed after new pump install. I know the pressure wouldnt be right if the dogbone was missing. Ive never forgotten one so I didnt get that Tshirt.

 

[Collinmcballin]

Have you changed brands of oil filters too?

My money is on worn bearings, cam bearings specifically.

Take a weekend on put new rings and bearings in the motor, sounds like you are young, healthy and knowledgeable enough to make this an easy peasy job!

Yes, I use only ac Delco but have used microguard in the past, been a few years in ac Delco.
I started using the pf61 as it's a taller filter, trying to protect this high milage beast haha.
I really appreciate it! I have some really good friends that would help me do that. Seems like a lot of extra tools. Eesh.

The weird part is that it can hold great oil pressure for even a few weeks after an oil change, then starts to drop. And when I go off roading it'll plummet and start rattling. Shut off for 15 min then I'm good, only goes back to 20psi..

 

[Collinmcballin]

Not likely the dogbone (left out) since you didnt take block down to rebuild fully. I suspect cam bearings is your problem if you replaced oil pump to fix the problem and the problem still existed after new pump install. I know the pressure wouldnt be right if the dogbone was missing. Ive never forgotten one so I didnt get that Tshirt.

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.

 

[rockola1971]

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.

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

 

[Collinmcballin]

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

Sh

Me personally at this point. Id pull the whole engine and have the block ran through. Pistons, Bored (Might as well go oversize), line honed and new bearings throughout. Atleast you dont have to worry about rebuilding the heads. Have them checked for flatness though. Dont be surprised that your cam is screwed and you are gonna need another.

Cam bearings could be done in the driveway but if its not done right you might end up needing another block after so I wouldnt chance it. Installing cam bearings while block is not completely torn down will be a pain especially still in the vehicle.

One day your 10psi is going to be ZERO and you will have proof when a rod is hanging out of your block.

Yeah no kidding haha. This last weekend was the lowest I've ever seen it. Never seen it below 20 except a hot day pushing it hard.
I just happen to stumble across the "oil pressure bypass/releif valve"? Little spring loaded pin where the filter mounts... Some guys are blocling/plugging it... Never seen it before hmm..

 

[rockola1971]

Sh

Yeah no kidding haha. This last weekend was the lowest I've ever seen it. Never seen it below 20 except a hot day pushing it hard.
I just happen to stumble across the "oil pressure bypass/releif valve"? Little spring loaded pin where the filter mounts... Some guys are blocling/plugging it... Never seen it before hmm..

That relief valve is there in case the oil filter gets plugged so the oil can just bypass the filter all together. That doesnt fit the bill with your cold ok or so so and then crap pressure when warm and improves with new oil. It takes alot of missed oil changes to get to the point where the bypass valve is actuating.

 

[Collinmcballin]

That relief valve is there in case the oil filter gets plugged so the oil can just bypass the filter all together. That doesnt fit the bill with your cold ok or so so and then crap pressure when warm and improves with new oil. It takes alot of missed oil changes to get to the point where the bypass valve is actuating.

Gotcha gotcha. Thanks for that insight. Mixed reviews from people on what it actually does lol
Yeah the previous owner definitely missed his oil changes. There was 1" of sludge when I dropped the pan. Last March...
Had the truck since 19'

Enter YouTube search of backyard engine building
And who has a cherry picker hahaha

 

[OR VietVet]

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!

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Collinmcballin]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

You are already receiving sage advice from the knowledgeable folks on this Forum.

It's awesome!! Thank you guys so much

 

[Collinmcballin]

seems to be great today. 160 miles on this oil.... I'm baffled

45° out

 

[Collinmcballin]

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!

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]

Gotcha gotcha. Thanks for that insight. Mixed reviews from people on what it actually does lol
Yeah the previous owner definitely missed his oil changes. There was 1" of sludge when I dropped the pan. Last March...
Had the truck since 19'

Enter YouTube search of backyard engine building
And who has a cherry picker hahaha

How does the oil look when you drain it?

 

[mattbta]

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.

 

[rockola1971]

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!