2008 5.3 AFM Oil Pressure problems

[TexasCowboy]

* Purchased used, had 96,000 or so miles on it, it's now at 104,000 so it is OUT OF WARRANTY
* Changed oil to Mobil 1 full synthetic about 300 miles ago, run only E85 in the engine to keep it cleaner.
* 1 mile from house, LOW OIL PRESSURE STOP IMMEDIATELY accompanied by chimes. Checked oil - barely registering on dipstick, other than that it had been between 40psi and 60psi consistently. Added 1.5 quarters, tried to drive home - half way there, LOW OIL PRESSURE STOP IMMEDIATELY.
* Had it flatbed trucked home, drained oil to inspect - what had been clear honey colored Mobil 1 was now jet black. Replaced with fresh 6 qt of Mobil 1 full synthetic, started again.
* Oil gauge will stay at 40psi for 2-3 minutes, then will progressively fall until it is near zero. Stop the engine for 30 seconds, restart and the same symptom.

Dealer quoted $1,260 to replace the pressure sending unit, ever so conveniently located on the rear of the engine and inaccessible unless you dismantle the top part of the engine or have hands the size of an elf.

Going to take it to my preferred dealer - Reliable Chevrolet in Richardson and ask them to diagnose the problem. From what I've read in the forums, it can be:

1. Spun bearning.
2. Dropped lifter.
3. AFM relief valve in oil pan.
4. Pressure sender filter screen.
5. Pressure sender.
6. Stuck rings due to AFM deactivation and carbon buildup.
7. Keebler elves - i mean really, can it be THAT hard to diagnose this problem?

I own 5 GM vehicles and have bought GM exclusively since 1992. My K1500 4WD never had this type of problem and I could work on that easily.

At this point, i'm going to ask the dealer to diagnose it and then take a hard look at replacing the engine with a new GM crate engine to get the warranty and a worry free 50,000 files on it. Since i'm out of warranty, this is going to be expensive, and my guess is in the $5,000-7,000 range for starters.

I'll post what happens, i'm assuming the dealer is going to diagnose it, get it wrong, have the problem recur, and then going through two or three fixes before it is actually solved - each time, charging me for the process.

 

[1929 Marmon]

2008 5.3 new eng.

TexasCowboy

Little confused why they would want to change the replace the pressure sending unit, as you stated it did its job.
I would never put synthetic oil in a used engine it cleaned it dropped every thing in the pump screen.
I would pull the pan and check the oil pump screen. Clean the pan and screen put oil back if same.
You sound about like I do about the dealer.
I would test the waters at a local junk yard on a used engine price it installed.
Was it knocking or rattling?
Good Luck
jim

 

[TexasCowboy]

Update on 12/26/2013:
1. Service advisor @ Reliable Chevrolet and I spent 20 minutes in the service drive, so that he could observe the PSI on the oil pressure gauge hit 60PSI when started, and then when the coolant temp approached 210 consistently drop minute by minute until the "LOW OIL PRESSURE STOP ENGINE IMMEDIATELY" accompanied by chimes. $99 to diagnose the issue and they won't get to look at it until tomorrow at the earliest and i would expect it to take 2-3 days to truly get to the point of knowing what the problem is.

Discussed a new GM crate engine which comes with a 100,000 mile or 36 month guarantee on it - i'm going to seriously consider that, depending on the diagnosis. If it's $2,0000 which is about the minimum i figure this is going to cost, then a $5,000 expense to replace the engine and get a guarantee on it doesn't sound so bad, and it caps my major repair costs for 3 years, so $2,000 per year doesn't sound too bad annualized.

Tried to discuss the 'known AFM concerns' which the service adviser down played but he did agree to confirm if the AFM changes had been installed on the vehicle.

 

[TexasCowboy]

Bad News

Bottom line, new engine.

Why? cracked heads, allowing coolant to mix with oil and then into bearings.

Out of warranty, $7,898.77 from dealer.

My choice to replace engine - it didn't make sense to replace heads for a couple of thousand, and still have a 104,000 mile engine that had coolant leaking into bearings - that's just a future nightmare.

New GM crate engine, with the AFM mods on it from the factory. New oil pump as well, new water pump, and a 36 month or 100,000 mile GM warranty - whichever comes first.

I'm not happy with the build quality from GM. I own 5 GM vehicles and exclusively buy GM.

In the future, i will look at consumer reports for reliability first and foremost over brand name badge on the truck - $8,000 is a LOT of money.

 

[GMC Customer Service]

* Purchased used, had 96,000 or so miles on it, it's now at 104,000 so it is OUT OF WARRANTY
* Changed oil to Mobil 1 full synthetic about 300 miles ago, run only E85 in the engine to keep it cleaner.
* 1 mile from house, LOW OIL PRESSURE STOP IMMEDIATELY accompanied by chimes. Checked oil - barely registering on dipstick, other than that it had been between 40psi and 60psi consistently. Added 1.5 quarters, tried to drive home - half way there, LOW OIL PRESSURE STOP IMMEDIATELY.
* Had it flatbed trucked home, drained oil to inspect - what had been clear honey colored Mobil 1 was now jet black. Replaced with fresh 6 qt of Mobil 1 full synthetic, started again.
* Oil gauge will stay at 40psi for 2-3 minutes, then will progressively fall until it is near zero. Stop the engine for 30 seconds, restart and the same symptom.

Dealer quoted $1,260 to replace the pressure sending unit, ever so conveniently located on the rear of the engine and inaccessible unless you dismantle the top part of the engine or have hands the size of an elf.

Going to take it to my preferred dealer - Reliable Chevrolet in Richardson and ask them to diagnose the problem. From what I've read in the forums, it can be:

1. Spun bearning.
2. Dropped lifter.
3. AFM relief valve in oil pan.
4. Pressure sender filter screen.
5. Pressure sender.
6. Stuck rings due to AFM deactivation and carbon buildup.
7. Keebler elves - i mean really, can it be THAT hard to diagnose this problem?

I own 5 GM vehicles and have bought GM exclusively since 1992. My K1500 4WD never had this type of problem and I could work on that easily.

At this point, i'm going to ask the dealer to diagnose it and then take a hard look at replacing the engine with a new GM crate engine to get the warranty and a worry free 50,000 files on it. Since i'm out of warranty, this is going to be expensive, and my guess is in the $5,000-7,000 range for starters.

I'll post what happens, i'm assuming the dealer is going to diagnose it, get it wrong, have the problem recur, and then going through two or three fixes before it is actually solved - each time, charging me for the process.

Hello TexasCowboy,

I am sorry to hear that you experienced this concern with your GMC vehicle when you were out of warranty and incurred this out of pocket expense. I am glad to hear that the dealership was able to address the concern. Thank you very much for updating your thread with the results from the dealership. I will definitely document your concerns in our database. Please don’t hesitate to reach out to me via private message if you have any further questions or concerns.

Gregory W.
GMC Customer Care

 

[DrBigJohn316]

I purchased my 08 Sierra brand new. I have had the same "low oil pressure" issue. The first time it happened had just broke 80,000 miles. Added a quart of oil and went on my way. At 90,000 mile it happened twice in one day. 23% oil life left and it was a quart and a half low. Truck runs fine as long as your driving, but as soon as I stop the motor feels like it's about to fall out the bottom. I brought to dealership ( I forgot about 5 year limit on 100,000 mile warranty ). Their diagnostic was seized lifters and for $4,056.00 they would replace lifters and cam shaft.
Asked dealership for price on new motor and it was $5,800.00 plus tax. I order a new motor from GM for $3,790.00 and install it myself. I can't believe that GM would not fix this problem. I called a local mechanic shop just to ask about dealerships diagnostic and they said sound right they have had five in one month.