At my wits end with oil pressure - please help

bsf24 · September 11, 2019

I have a 2012 5.3 with 125k. I've owned since around 90k. Basically, the oil pressure drops between oil changes. After an oil change the truck maintains decent pressure, maybe 30 or so when hot driving down the highway. After I get down to about 60% on the oil life indicator it starts to drop when hot, until eventually it's running 20psi at 70mph on the highway and triggers the CEL and code P0521. I'm using 5w30 Mobil 1 and have tried all sorts of filters, (Royal purple, Mobil 1, Delco, etc.)

The truck makes no noises on a cold start, or when hot, it runs beautifully regardless of where I'm at pressure wise.

I've replaced the oil pressure sensor sending unit, the screen beneath the oil pressure sending unit, the oil pump, and the lifter o-ring. The problem persists. I'm at my wits end. I'm not sure where to go next. I'm thinking I just might get rid of the truck. Please help. I don't know where to go next.

Edited September 11, 2019 by bsf24

CamGTP · September 11, 2019

I guess choosing a different oil brand is the last option but that doesn't really sound it will mean much.

Have you been able to hook up a mechanical oil pressure gauge when this issue starts to happen to make sure that it's reading what the dash reads?

bsf24 · September 12, 2019

31 minutes ago, CamGTP said:

I guess choosing a different oil brand is the last option but that doesn't really sound it will mean much.

Have you been able to hook up a mechanical oil pressure gauge when this issue starts to happen to make sure that it's reading what the dash reads?

I have. The dash gauge is accurate.

Mikebtte · September 12, 2019

What is the time frame for 60% and how many miles. I never used the % thing as it would let me run up 10K miles if I did.

Could be a faulty sensor, clogged screen, failing oil pump, oil pressure releaf valve failure. The list goes on but nothing that can justify. Getting rid of the truck. All easy fixes.

There is a port on the front D/S of the block coming right off the oil pump. If it's reading the same than I would put on a pump and pump Oring.

Calm down, relax and kick this problem with a little diagnosis.

Edited September 12, 2019 by Mikebtte
Removed die to already hooked up manual gauge

bsf24 · September 12, 2019

19 minutes ago, Mikebtte said:

What is the time frame for 60% and how many miles. I never used the % thing as it would let me run up 10K miles if I did.

Could be a faulty sensor, clogged screen, failing oil pump, oil pressure releaf valve failure. The list goes on but nothing that can justify. Getting rid of the truck. All easy fixes.

There is a port on the front D/S of the block coming right off the oil pump. If it's reading the same than I would put on a pump and pump Oring.

Calm down, relax and kick this problem with a little diagnosis.

I appreciate the reply, but did you read my post?

I have changed the sensor, replaced the screen, replaced the pump, o-ring, and lifter o-ring, and replaced the relief valve.

Mikebtte · September 12, 2019

1 hour ago, bsf24 said:

I appreciate the reply, but did you read my post?

I have changed the sensor, replaced the screen, replaced the pump, o-ring, and lifter o-ring, and replaced the relief valve.

I have a short attention span. Lost me after the first paragraph sorry.

anyhow, Have you check pressure at the pump to see if the pressure is lost at the pump or if you are loosing it down stream.

behind the rear housing seal is a plug that can leak as well. Plug is used to fill the casting that was drilled during manufacturing

There is a plug underneath the front cover that is just like a freeze plug. It is a pressed in plug. If that is leaking or has been pushed out at all, you will bleed pressure back into the pan.

Edited September 12, 2019 by Mikebtte

Mikebtte · September 12, 2019

Hate to point at AFM, but I wonder if it could be in relation to the valley cover ether not closing off completely or leaking.

jay webb · September 12, 2019

when this starts to happen have you checked your oil level? is it low? is it consuming oil?

best way to check this is... after driving it and its at operating temp let it sit for about 15 mins, check the level on the dipstick ... top off to full. note the amount you topped off with and how many miles.

typically we do this every 1000 miles for an oil consumption test. if i remember correctly these trucks have an issue with the pvc system in the valve cover and their is an updated part to replace the valve cover/pvc system , it can cause oil consumption.

bsf24 · September 12, 2019

22 hours ago, Mikebtte said:

Hate to point at AFM, but I wonder if it could be in relation to the valley cover ether not closing off completely or leaking.

Would this explain why it happens about 1500-2000 miles after an oil change?

22 hours ago, Mikebtte said:

I have a short attention span. Lost me after the first paragraph sorry.

anyhow, Have you check pressure at the pump to see if the pressure is lost at the pump or if you are loosing it down stream.

behind the rear housing seal is a plug that can leak as well. Plug is used to fill the casting that was drilled during manufacturing

There is a plug underneath the front cover that is just like a freeze plug. It is a pressed in plug. If that is leaking or has been pushed out at all, you will bleed pressure back into the pan.

Where is this on the engine? I know you said on the front cover but I'm wondering if there's another photo/diagram somewhere?

20 hours ago, jay webb said:

when this starts to happen have you checked your oil level? is it low? is it consuming oil?

best way to check this is... after driving it and its at operating temp let it sit for about 15 mins, check the level on the dipstick ... top off to full. note the amount you topped off with and how many miles.

typically we do this every 1000 miles for an oil consumption test. if i remember correctly these trucks have an issue with the pvc system in the valve cover and their is an updated part to replace the valve cover/pvc system , it can cause oil consumption.

It doesn't really burn oil. Maybe a half a quart between changes? Nothing crazy.

Mikebtte · September 13, 2019

40 minutes ago, bsf24 said:

Would this explain why it happens about 1500-2000 miles after an oil change?

Where is this on the engine? I know you said on the front cover but I'm wondering if there's another photo/diagram somewhere?

Possible, weird that is consistently does it at a set interval. That's why I was thinking AFM top plate. That is nor serviceable and I know some claim to have developed a new advanced design.

Oil plug is on the front. Bar bell is in the rear.

Mikebtte · September 13, 2019

If one of the AFM solenoids is hanging up it would cause erratic oil pressure changes. As you can see in the diagram, oil pressure is release here. I would think it would also run different, but not 100%

Bad Bowtie2 · September 14, 2019

What brand oil filter & weight of oil are you using??

bg1988 · September 16, 2019

On 9/11/2019 at 3:59 PM, bsf24 said:

I have a 2012 5.3 with 125k. I've owned since around 90k. Basically, the oil pressure drops between oil changes. After an oil change the truck maintains decent pressure, maybe 30 or so when hot driving down the highway. After I get down to about 60% on the oil life indicator it starts to drop when hot, until eventually it's running 20psi at 70mph on the highway and triggers the CEL and code P0521. I'm using 5w30 Mobil 1 and have tried all sorts of filters, (Royal purple, Mobil 1, Delco, etc.)

The truck makes no noises on a cold start, or when hot, it runs beautifully regardless of where I'm at pressure wise.

I've replaced the oil pressure sensor sending unit, the screen beneath the oil pressure sending unit, the oil pump, and the lifter o-ring. The problem persists. I'm at my wits end. I'm not sure where to go next. I'm thinking I just might get rid of the truck. Please help. I don't know where to go next.

30 PSI is pretty low

the engine is very worn out and the space between the metals has a big gap.. causing loss of pressure

Mine has a continuously Variable oil pump installed though

i'm hitting 70-75PSI cold start (even if it's like 100F degrees outside) and

50-55PSI idle speed#2 (100RPM)

45Idle idle speed #1(600rpm)

once warmed up and driving for a while

mobil1 is great oil and the engine works really well i used 1qt of 0w30 and 5qt of 5w30

it had lower the start up psi by a few as i'm worried it might blow out the seals or something..

(600 and 1,000rpm is idle speed for my engine it has a variable idle speed because of the hybrid motors)

This engine is sludge Free with 92k miles not even a speck of dirt in the oil with 2000 on the current oil change.. i might see a few specks at 4,000 miles

is sounds like you have coolant or fuel contaminating the oil I would send it off for an oil analysis... to find out in the mean time i would be using motorkote in the engine

1qt to 5 qt of oil

it's very expensive but it might just save your engine in the meantime

the drop in oil level is enough to cause the pressure to drop

.. since it becomes worse "after your down 1 qt of oil"

this could also suggest you have oil pooling up elsewhere in the engine from a clog drain tube upstream of the oil pan

or vapor lock in the oil cooler line...(these lines are not leaking correct??)

CHECK the oil level when it's having Low PSI...(if none or very low on the dip stick then it's pooling elsewhere in the engine)

This hybrid Vortec Engine has seen pretty heavy abuse The crankshaft has seen

Well over 200,000 Stops and stat cycles. NOW THATS A LOT OF DAMAGE..

in it's current life. about 2 to 4 cycles for every mile it has driven (it has lived in the city of Los Angeles and has some la stop and go freeway miles as well)

Edited September 16, 2019 by bg1988