2001 Burban, almost no oil pressure even after replacing the oil pump

[91RS]

My guess is you've got cracked head(s) and the cam bearings are wiped. I would stop wasting time and money on that engine and buy a used engine and swap it out.

 

[ScottyBoy]

Short trips are the worst for engines.

Perhaps that's my problem then. I ONLY drive my truck to work, that's pretty much it. Anywhere else, I take the wife's car, or we both ride together in her car. I only work about 5 miles from home, so it takes me 10-15 minutes at MOST to drive to work.

 

[OR VietVet]

Short trips, like @Larryjb and myself and others are saying, are tough on the engine and build that condensation/moisture internally and when shut off engine that moisture drips in to the oil. Easiest time on engine is on the hiway at a cruise speed. Not accelerate and decel in town or even on the hiway and damn sure not short trips. Rigs like to be driven.

How stupid is it that instead of saying H-A-R-D O-N an engine I have to say tough on an engine.....

 

[Manuel Turchan]

maybe worn or scored babbit bearings
At 3,ooo miles my '09 Tahoe needed new crank and cam bearings 'cause the
metal shavings from original machining weren't cleaned out completely. That led to zero oil pressure.

About the same time, had to tear down transmission due to bad o-rings in valve body.

GM covered all the warranty but the dealer was out to lunch, didn't believe the trans problem even after test drive. said it was normal to feel like you get a kick in the rear as the trans downshifted.

Hired an attorney 'cause I was without my Tahoe for nearly 2 months during first 4 months ownership.
Best he could do was $3,000 under lemon law, all I asked was to warranty the next 100k miles. GM was smarter than that.

 

[jwth]

In the old days we would put a can of CD2 additive in the oil to clean blocked passages and quit lifter noise. Then change the oil after 200 miles of driving-- at least 30 minutes each time. Sseem to work wonders for low oil pressure due to blockages and quiet load lifters.

just a suggestion, I do it to mine still.

 

[iamdub]

Well I'm hearing LOTS of mixed opinions then. Some folks claim it CAN break down simply with age. Some claim that you can go up to 12k or 15k miles on some oils regardless of how many months or years it takes to go that many miles.

As the others have said, the oil you're using and the low annual mileage aren't the problems. Synthetic doesn't break down over time anywhere nearly as quickly as conventional. @kbuskill runs his oil for (IIRC) a year and ~10K+ miles, probably more at this point. He has a special filtration setup to keep the oil clean, but the properties of the oil itself are perfectly fine for service. Comparing a stock setup, I change mine at 5K and have gone a year or two with one annual change each. Pics of my engine's tear-down show annual oil changes are fine. The key is, even if driven minimally per year, is to drive it long enough to burn off the condensation when it is driven. Otherwise, the condensation will collect. Water in the oil, whether it's synthetic or conventional, will cause sludge to build.

Your sludge being pretty much 100% in the pan tells me it's sludge that was once all throughout the engine but, over time, has been dissolved from those surfaces and has settled in the pan. It's "old sludge". Your short trips are only adding to the problem by introducing more moisture.

As for the low oil pressure, the best case is that you have an internal leak in the system- Botched O-ring install would be about the only likely possibility. A broken barbell could cause low pressure, but that is HIGHLY unlikely to happen. I've heard of the pressure release valve in the oil pump getting wedged open by a piece of metal left behind from machining. But, it would have to have developed high pressure to begin with to push the valve's plunger to that position in the first place.

Worst case, the time it has been ran with no or very little oil pressure wiped out the bearings, increasing the clearances so much that they're not tight enough to build pressure. This usually would take time and you'd notice a gradual decline in the pressure range. A sudden loss of oil pressure would've alerted you with an instantly plummeting gauge, warnings in the DIC and a nearly immediate lifter clacking since they're hydraulic and rely on oil pressure to remain solid. If the bearings were damaged from oil starvation, it's possible that one or some could have seized and spun. Sometimes a spun bearing can be mistaken as a lifter tap.

 

[Fless]

Just before an oil change I have run BG EPR (and MOA in the new oil afterward) for cleaning purposes. Not often, near 100K in my former DD.

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When running the EPR the oil gets hot (seems like a bit hotter than usual) and it comes out super black, with crud in suspension. Might be worth a try.

 

[Tonyrodz]

Sometimes a spun bearing can be mistaken as a lifter tap.

As was my case with my 1st 6.0.

 

[ScottyBoy]

You guys have me thinking now that I might have a spun bearing. But can a spun bearing quiet itself down like a lifter tap? If so, then everything you guys are describing are all signs of a spun bearing. I had no gradual loss in pressure, it all went out at once. The day it happened I had just pulled into the parking garage at work. I slightly accelerated to get to the upper floor and then the gauge plummeted to zero along with a "Check Engine Oil Pressure" warning light on the dash. As far as the lifters clacking, no they didn't start clacking but I'm not sure I let it run long enough to even give them the chance to start clacking. Literally 15-20 seconds after the warning light came on I shut the engine off. Because I pulled into the first parking spot I saw and shut it off IMMEDIATELY after seeing that I had no oil pressure. Next day I had it towed home (after finally getting it out of the garage. Tow truck couldn't fit into the parking garage because low ceiling height). Then after checking the oil pressure with a manual gauge, I decided to replace the oil pump. The first engine startup after replacing the pump, I heard a loud clacking which I assumed to be a lifter since I've heard a nearly identical noise in the past and was told it was a lifter. Engine only had about 20psi at most, but I still let it idle and warm up. After about a minute or just barely longer than a minute, the clacking nearly stopped, or at least 90% of the noise went away. (Yet another reason I assumed it to be a lifter, as this is how they done in the past the few times it's gotten REALLY noisy).

 

[iamdub]

You guys have me thinking now that I might have a spun bearing. But can a spun bearing quiet itself down like a lifter tap? If so, then everything you guys are describing are all signs of a spun bearing. I had no gradual loss in pressure, it all went out at once. The day it happened I had just pulled into the parking garage at work. I slightly accelerated to get to the upper floor and then the gauge plummeted to zero along with a "Check Engine Oil Pressure" warning light on the dash. As far as the lifters clacking, no they didn't start clacking but I'm not sure I let it run long enough to even give them the chance to start clacking. Literally 15-20 seconds after the warning light came on I shut the engine off. Because I pulled into the first parking spot I saw and shut it off IMMEDIATELY after seeing that I had no oil pressure. Next day I had it towed home (after finally getting it out of the garage. Tow truck couldn't fit into the parking garage because low ceiling height). Then after checking the oil pressure with a manual gauge, I decided to replace the oil pump. The first engine startup after replacing the pump, I heard a loud clacking which I assumed to be a lifter since I've heard a nearly identical noise in the past and was told it was a lifter. Engine only had about 20psi at most, but I still let it idle and warm up. After about a minute or just barely longer than a minute, the clacking nearly stopped, or at least 90% of the noise went away. (Yet another reason I assumed it to be a lifter, as this is how they done in the past the few times it's gotten REALLY noisy).

If the bearing spins and wears down whatever is clacking, yes, it can quiet down. You'd never see the metal shaving because of all the sludge. You could slosh a strong magnet through it to see what it'd pick up. Most of the bearing material itself is aluminum, so you'd be picking up journal and main material.