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Discussion Starter #1
Before I take any drastic steps, I'm looking for input from those who may have been in the same situation with low oil pressure and the P0521 CEL.

Backstory:
In November, at 60k miles, a trunion upgrade let a needle bearing find its way to destroying the #8 lobes on the cam. So to not skip any steps, I pulled the shortblock and had it gone through by Rob Mahler, owners of Mahler Machine in Collingdale. He's done BBC and Buick work for me in the past, and also does a lot of machining and assembly work for east coast performance shops--so there's a confidence there.

In addition to cleaning the block, checking the rotating assembly and putting the shortblock back together for me, Rob also did a valve job done and confirmed all hard parts were in good shape. I reordered the cam from Comp, and updgraded to an HV Melling plus all the normal wearable items putting an LS back together.

Once back in the car, it had good oil pressure and no CELs. Filled it with 7 qts Mobil1 5/30 with 2 qts 30wt breakin oil (zinc addiditve) for 300 miles when the first CEL P0521 occurred at a hot idle.

We cleared the code and changed the oil, it appeared I was good to go. While I didn't cut the filter at the time, I did pay attention to the magnetized drain plug looking for anything suspicious. Everything looked good, and a TechII showed it only dip into the mid/high 20's after sitting hot idle for ~15 minutes.

I used a new filter, 8 qts Mobil1 5/30 and 1 qt 30wt break in.

Now:
Nearing the next oil change interval, around 63k miles, the P0521 came back about two weeks ago. Again the hot idle reading was low for an LS, now dipping low/mid 20's. Cleared the code, and it would come back.

Changed the oil for the second time, new filter 9 qts Mobil1 5/30 and no 30wt. Code clears, cold idle 50-55psi but dips to 20's on a scanner.

A week ago I ordered a mechanical oil pressure gauge and fittings to rule out the Oil Pressure Sensor, but in the meantime had also picked up a DashBoss.

Using the DashBoss I was monitoring one of the three oil parameters on the way to work today, oil pressure drops into 20's when the car warms to 190* and is under 1,000rpm.

Pressure builds into 40's with increased RPM, but pulling into the parking lot saw it dip as low as 10-11psi :nonono:

Appreciate your time if you've read this far... So, thoughts?

Pull the motor and dig in, or can anyone offer another less-invasive suggestion? The oil isn't frothy after running, but I can't rule out the seal at the pickup or oil pump. I've read here that it could be the pressure relief valve in the pan too.
 

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Discussion Starter #3 (Edited)
The trunion kit was from Comp, when the engine went back together this last time I used brand new GM rockers.

The sensor has not been replaced at this point because the pressure levels being observed through the ECU are consistent. I'm planning to put a mechanical gauge as soon as the parts get here--hopefully by the weekend.

I want to add, the motor still sounds healthy. Nothing out of the ordinary as far as the outside goes.
 

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Your oil pressure symptoms sound exactly what mine was doing. I just rebuilt mine since it needed to be forged too. You need to check for a stuck bypass valve on the oil pump too.
 

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There's a pressure relief valve in the oil pan that can also get debris caught in it making it get stuck open. Might be worth your efforts to drop the pan and remove or replace that relief valve.
 

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Discussion Starter #6
Can the pan come out without pulling the motor? If so I could check the pickup seal at the same time--I wish I knew about that valve while it was apart the first time.
 

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Yes, it can come out without pulling the engine. You have to remove the engine mount nuts and jack the engine up a couple inches, or set the engine mounts on top of a 2x4. Pull the pan and replace the valve, or plug it if you don't have DoD. You can use an oil pan drain plug bolt with some loctite on it to plug the hole where the relief valve is. If you car still has DoD, then you cant plug the hole and you MUST replace the relief valve.
 

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Discussion Starter #8
The DOD stuff was all deleted, so this looks like a good first step. I'll update once we're into it--
 

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Just make sure when you put the pan back on, you dab some sealant / RTV where the front and rear cover joints meet the block, then put the pan on. This will keep oil from seeping out of these joints. Loctite 5900 is the best sealant i have ever used for engine assembly, if you can afford it, get some of that stuff.
 

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There's an I ring that has to sit inside the pump from the pick up tube exactly right. When I had pressure issues after a cam install it was because that didn't seat proper and I had to redo it. Might be worth a check since you did swap cams.
 

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Discussion Starter #11
Update:

Pan came off, deleted the DOD pressure valve. The pickup tube looked good, but still pulled down and reinstalled. There was a tiny bit of bearing material in the bottom of the pan that I cleaned out while I was in there.

Pulled the front cover to check the oil pump bipass valve and spring, but did not remove the pump. It looked good, so I buttoned it back up and filled it with 15/50.

Still quiet, with no knock or rattle. Got cold start in the 50psi+, and 30psi+ hot above 1000RPM. Idling below that drops L O W. The dashboss has two oil pressure parameters to monitor, both are shown below. Since there was no change after all this, I installed a temporary mechanical gauge to confirm pressure using this above the oil filter.
Pressure is consistent from cold start through full warm up.




Looks like it's coming back out :judge:
 

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Those pressure are actually not bad, but here's some more info

Here's a GM Service Bulletin Regarding Trouble Code P0521......that maybe able to help you.

GM Service Bulletin: PIP4786: Low Oil Pressure Message Light - Inspect Valve Lifter Oil Filter - (Apr 5, 2010)

Subject: Low Oil Pressure Message/Light - Inspect Valve Lifter Oil Filter
Models: 2007 Cadillac Escalade

Built before April 1, 2006 with 6.2L L92 Engine
(These engines were built with AFM Hardware but the AFM system was disabled.)

2009 Buick Lacrosse Super, Allure Super (Canada Only)
2005-2007 Buick Rainier
2010 Chevrolet Camaro SS
2007-2010 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2007-2009 Chevrolet Impala
2005-2009 Chevrolet Trailblazer
2007 Chevrolet Monte Carlo
2007-2010 GMC Sierra, Yukon
2005-2009 GMC Envoy
2007-2008 Pontiac Grand Prix
2008-2009 Pontiac G8
2005-2009 Saab 97x

With an AFM (Active Fuel Management) V8 Engine RPO: L76, L94, L99, LC9, LFA, LH6, LMG, LS4, or LY5

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concerns: Some customers may complain of a low oil pressure message/light on the dash and a technician may find a Po521 DTC in the ECM.

Recommendation/Instructions: If this concern is encountered, follow SI diagnosis. If it indicates that the Tech 2 oil pressure parameter is low but proper oil pressure is present at the oil filter housing, inspect the Valve Lifter Oil Filter for debris/sludge that could be restricting oil flow to the oil pressure sensor before replacing any parts.

Follow the Valve Lifter Oil Filter Removal and Installation Procedure to remove the filter for inspection. If the filter is plugged, it can normally be cleaned with brake/contact cleaner and light shop air. If it cannot be cleaned for some reason, replace it using the part number listed in the parts catalog. Do not replace the complete Valve Lifter Oil Manifold just because the filter is plugged.

#452 - Valve Lifter Oil Filter

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the information.
 

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  1. Remove the oil pressure sensor (1) and washer (2) from the Valve Lifter Oil Manifold (VLOM) (5).
Important: The valve lifter oil filter (3) should be replaced whenever the oil pressure sensor (1) is removed.



  1. Remove the valve lifter oil filter (3). Discard the filter.
Important: The valve lifter oil filter O-ring seal (4) is a single use only part and must be replaced whenever the valve lifter oil filter (3) is removed.



  1. Remove and discard the valve lifter oil filter O-ring seal (4). Discard the O-ring seal.
 

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Cam bearings have also been know for leakage and low pressure in LS motors. Check if Mahler changed them when they had the engine.
 

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Discussion Starter #15
Cam bearing were done at the same time as everything else. Talked to Mahler today and he'll be digging into it as soon as I can get it to him.

Engine came out today, so hopefully we can drop it by Monday. Will update further once it's opened back up.

Thanks all for the help so far, good info for anyone searching on the topic in the future--
 

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Discussion Starter #16
Good news? the rods and pistons are all good
Bad news? crank and block are trashed

It looks like the crank was pushed forward, causing the Thrust Bearings to get chewed up. There's a ton of play on the crank, and best guess is the trans decided to push the (stock) converter creating serious pressure on the backside of the crank effectively wasting the block and crank. I've heard of converters ballooning, but not on a basic H/C set up with stock converter and trans.

Surprisingly, the rods and mains look really good--just the thrust bearings are trash.

Murphy's Law. Fail. FML. etc...
 

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Awe man that sux man!! Sorry to hear that. Im not having much luck on my project either!! Everything keeps costing more money........
 

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Check the trans. If the converter was not fully seated that would have pushed the crank but also could have damaged the converter and front pump.
 

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Good news? the rods and pistons are all good
Bad news? crank and block are trashed

It looks like the crank was pushed forward, causing the Thrust Bearings to get chewed up. There's a ton of play on the crank, and best guess is the trans decided to push the (stock) converter creating serious pressure on the backside of the crank effectively wasting the block and crank. I've heard of converters ballooning, but not on a basic H/C set up with stock converter and trans.

Surprisingly, the rods and mains look really good--just the thrust bearings are trash.

Murphy's Law. Fail. FML. etc...
http://www.g8board.com/forums/5-v8-engine-tech-l76-ls3/241618-check-oil-light-no-syptoms.html

kindly....take a look on the tread...pls
 

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So I have read a lot of post because of the code 0521. I am now getting the code 0531. Never had any issues car is a 2008 G8 GT. Stock. Coming off a HWY one day and watched the stock pressure gauge go to zero. Pulled over immediately. Got ride home and early the next day changed the oil sensor. Got oil pressure back and it never threw a code.
But 2 days later started throwing code 0521. Changed sensor again and am still getting code. Now I have read many post and some guys are pulling engins. Tomorrow I will change the oil and filter. Will let you know.
KK
 
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