Low oil pressure on new rebuilt motor

brewer · Apr 1, 2018

Long story short, I had a rebuilt motor installed recently. Motor was built by a local machine shop and the shop that was installing it. Not dealing with the "install" shop anymore because of some bad experiences/poor management over all this.

When they got the truck running, it had a knock on the rear passenger side when cold. Goes away when warm. Got the truck home, and pulled the injectors and sent them to Unlimited to look through the oil sides. Found no issues with them.

Got the injectors re-installed, took the truck out for a test drive, and still have a knock cold. Cylinder contribution test and buzz test show no issues.

However, at warm idle, the oil pressure drops down below the 7psi cutoff for the dash gauge. Pressure comes back up with RPMs.
I also have some kind of a buzzing/whine/humming noise coming from the front of the engine when cold. I am wondering if this may be the LPOP from low oil pressure although the HPOP reservoir stays full. Could also be my power steering pump. It is similar to the notorious Ford power steering whine.

Measured the oil pressure at the HPOP reservoir and the oil cooler test port with a manual gauge. They both read about 50-60psi cold idle, then drop down to about 15-20psi as the truck starts to warm up after like 10 min idling.

I am thinking that the passenger side oil galley plug may be missing. But could that be causing a knock too? Could it be lifter knock from low oil pressure on that side?

Magnum PD · Apr 1, 2018

It could be a lifter or one of the plugs in the back of block.

lincolnlocker · Apr 1, 2018

If you have a oil galley plug missing then you will have oil leaking.. and not just a slow one..

live life full throttle

brewer · Apr 1, 2018

lincolnlocker said:
If you have a oil galley plug missing then you will have oil leaking.. and not just a slow one..

live life full throttle

By oil galley I am referring to the LPO galley that feeds the lifters, etc. and not the HPO rail. The pressed in cap on the back of the block behind the rear cover.

lincolnlocker · Apr 1, 2018

brewer said:
By oil galley I am referring to the LPO galley that feeds the lifters, etc. and not the HPO rail. The pressed in cap on the back of the block behind the rear cover.

Regardless, it wouldnt be a slow leak and prolly wouldnt even start if that was the case. So i doubt it is that. Unless you have oil runing down and on the ground everytime you start it.

live life full throttle

Magnum PD · Apr 1, 2018

You’ll have to take everything off to see that plug. Trans and plate on back of the block.

mandkole · Apr 2, 2018

This is depressing.. ugh

I would be sure to compare the pressure at the reservoir and from the plug between the oil filter and the cooler. The noise could be a rubbing/bad fit pump.

brewer · Apr 2, 2018

mandkole said:
This is depressing.. ugh

I can't disagree w/ that lol.

mandkole said:
I would be sure to compare the pressure at the reservoir and from the plug between the oil filter and the cooler. The noise could be a rubbing/bad fit pump.

It appeared to be about the same. Started around 50-60 psi at first cold startup, then dropped down to around 15-20psi after about 5-10min idling, and oil temp was warming up.

The weirdest part about watching the gauge at the oil cooler header was that it was fluttering a decent amount. It never really calmed down until right about when I shut it off when it was at like 17 psi. The HPOP reservoir didn't cause any flutter. Is the gauge flutter normal there? Should I have let it idle longer to see what happened?

6.0 Tech · Apr 3, 2018

Is there a chit ton of silicone on the pan or anywhere fairly visible? I have seen multiple times excessive silicone plug pick up screens and what not. Charlie from KC Turbos had a shop.rebuild one of his 6.0 motors, and silicone had plugged everything up, and either hey had forgotten to install, or they got blown out, oil galley plugs like you mentioned at first. That is a definite possibility. It would have to be an internal one, like behind the rear main or something, if there is one there, or internal in the head, otherwise it would piss on the ground like a scared puppy, which is what lincolnlocker was saying.

brewer · Apr 3, 2018

6.0 Tech said:
Is there a chit ton of silicone on the pan or anywhere fairly visible? I have seen multiple times excessive silicone plug pick up screens and what not. Charlie from KC Turbos had a shop.rebuild one of his 6.0 motors, and silicone had plugged everything up, and either hey had forgotten to install, or they got blown out, oil galley plugs like you mentioned at first. That is a definite possibility. It would have to be an internal one, like behind the rear main or something, if there is one there, or internal in the head, otherwise it would piss on the ground like a scared puppy, which is what lincolnlocker was saying.

Nope, the motor appears to be well put together other than a freeze plug on the passenger front of the block that has been weeping here and there. Still waiting to see if that seals itself but that is the least of my worries at this point. And I found a couple damaged bolt heads on the valve covers.
I think at this point I am going to just pull the passenger valve cover off again and unhook some of the rear injectors to see if I can narrow down which cylinder is making the noise at cold idle. I figure it's possible there's still an injector issue. But still I may have two separate issues here: injector issues and missing galley plug/other.
And then maybe put the manual gauge back on the oil cooler and let it get nice and warm and watch what it does there.
All this started because the block cracked at the oil cooler header like many other early trucks have like mine. This whole process has fought me every step of the way.

BS Hauler · Apr 3, 2018

Is it possible that you are having oil aeration.

brewer · Apr 3, 2018

BS Hauler said:
Is it possible that you are having oil aeration.

What do you mean by that?

Magnum PD · Apr 3, 2018

Your pickup tube could be getting air from sucking air in a nonsealed place

brewer · Apr 3, 2018

Magnum PD said:
Your pickup tube could be getting air from sucking air in a nonsealed place

And would that air possibly be from a missing internal oil galley plug?
Would the aeration cause lifter or injector noise?

Magnum PD · Apr 3, 2018

I was referring to the actual pick tube, Like a hole or gasket failure in it.

Only way to tell about a missing oil plug in the back of the engine is to pull the trans and take rear cover off.

brewer · Apr 4, 2018

Allowed the truck to idle for about 20 min, and watched the pressure at the regulator in the oil cooler. It dropped down to about 15 psi but fluctuates about 2 psi +/- as it idles. As it fluctuates, RPMs fluctuate as well.
When I put it in drive, oil pressure drops down to around 9-10 psi for about 2 seconds and the truck bogs down as if its about to die, then pressure and RPMs come back up to about 15psi and idle RPMs.
I am leaning towards pulling the oil cooler to check that valve.
Any thoughts on that?