Low Oil Pressure ,Next Step

[2014PPV]

2014 Tahoe PPV 5.3 146000 miles

Problem :Low oil pressure.

Symptoms: Check Engine Light, No noticeable ticking or unusual engine noise, No Stop Engine Warning

Work Performed so far: Change oil and filter using GM parts. Replaced pressure sensor and screen, and pickup tube O ring.

Manual check of oil pressure @ oil filter # 26 on startup # 20after warmup @800
Manual check of oil pressure @ sensor #20 on startup # 10 after warmup @800

Trying to decide if I should change out the oil pump or what the next step should be. Any constructive advice would be appreciated.

 

[Geotrash]

2014 Tahoe PPV 5.3 146000 miles

Problem :Low oil pressure.

Symptoms: Check Engine Light, No noticeable ticking or unusual engine noise, No Stop Engine Warning

Work Performed so far: Change oil and filter using GM parts. Replaced pressure sensor and screen, and pickup tube O ring.

Manual check of oil pressure @ oil filter # 26 on startup # 20after warmup @800
Manual check of oil pressure @ sensor #20 on startup # 10 after warmup @800

Trying to decide if I should change out the oil pump or what the next step should be. Any constructive advice would be appreciated.

Bummer man. There are a few things that can cause low oil pressure beyond what you're tried so far:

1/ Are you sure you installed the correct o-ring in your pickup tube? Also, sometimes they can get nicked slightly on install. Happened to me and I had to pull it out all over again.
2/ Oil pump can indeed be the problem. When I did the o-ring the second time, I just went ahead and replaced the pump with a Melling high volume unit and used their thick green o-ring. It's slightly thicker even than the OEM one is for this engine. No more problems.
3/ Cam bearing wear can also cause this problem. As a PPV yours likely has many, many idling hours on it.
4/ Bad pressure spring in the oil pump outlet.
5/ Dog bone in the oil gallery at the rear of the engine can leak and bleed off pressure.
6/ Pressure relief valve in the oil pan can stick and cause low oil pressure.

 

[2014PPV]

I decided to replace the oil pump with a Melling high-volume pump. I have it broken down to replace oil pump waiting for the parts to arrive. I check the oring on the pickup tube and it was a tight fit. The pressure relief valve in the oil pan seemed O.K. but will replace it just to be sure. The oil pump has some wear but nothing significate. The pressure relief piston looked good and did not seem to be sticking, not sure about the spring. I'm really thinking it's the cam bearings but hoping the HV pump will make some difference until I can have someone who knows better equipped to replace the bearings or do a motor swap.

 

[j91z28d1]

that does seem low. following along to see what you find forsure.

for more story, what oil are you running, and how many miles on the oil at the test? you're pretty close to what I've seen listed as service limits.. have you checked the vlom cover bolts to see if they lose? I have seen theorys when they are lose it can bypass oil.

also there is a 2nd option no one really consideres or know exists, but the variable displacement pump from the hybrid is said to fit any ls.. seen some posts on the corvette sites about them. the newer LT engines switched to variable displacement pumps on all of them. millings has a part number listed. they are said to save 1.5hp.. and judging by my truck. run high pressure. mines like 40 at idle on super hot day long trip and high mile oil. sits on 60 mark most other times. I'm guessing that's the afm bypass psi of 58 ish. good enough I'm going to try 0w20 next change.

before you pulled it all apart, did you consider just running a thicker oil? like a 10w40?

 

[2014PPV]

Before running the test I changed the oil using 10w-30 synthetic. I tried 10w-30 with a quart of Lucas HD oil stabilizer prior to the manual test with no noticeable change in idle oil pressure. I failed to mention at approx. 2500 rpm I have 30 # of pressure after warmup. I was hoping the pressure drop at idle after warmup would help point me in the right direction of what the problem may be.
I will check the vlom cover bolts to see if they are loose as you suggested.

 

[j91z28d1]

man, I'm supised Lucas didn't bring it up a lot. I've got some old worn out Detroit diesel engines at work.. they idle about 2 psi when warm and set off lights on 15w50. add some Lucas and they come right up and idle with decent pressure. that stuff is thick

Humm. interesting to see the results.

 

[2014PPV]

Finally, installed the Melling high-volume pump along with a new bypass spring that is mounted in the oil pan and fresh 10w-30 synthetic. I have not performed a manual oil pressure check, but I am still only getting 20 # at 600-700 Idle on startup and 12 #at 600-700 idle on the gauges. Check engine light has cleared. I only getting about 25#at 60 mph (I stated 30# in my first post but I believe I was incorrect).

 

[strutaeng]

It's probably your bearing clearances then. You don't have the AFM stuff, do you?

I would switch to higher oil weight and keep running it, but have an overhaul in mind for the future.

 

[Dustin Jackson]

I agree might as well continue to run it while it still runs and rebuild it. The damage is already done to the wear parts of the motor but they can be replaced.

 

[2014PPV]

"It's probably your bearing clearances then." I agree and yes I still have the AFM stuff

 

[strutaeng]

"It's probably your bearing clearances then." I agree and yes I still have the AFM stuff

I ask because I thought the AFM required higher oil pressure to work properly? I'm only familiar with the Gen III, not much on the Gen IV+.

I ran the 4.3 in my 99 Silverado for 10,000 miles with low oil pressure before I retired the engine. It had about 5 psi at summer hot idle checked with a mechanical guage when I started getting low oil pressure. My dash guage was below zero and the check gauges light came on at stoplights. I switched to 50 grade oil and pressure improved to around 8 psi and I kept running because I didn't have the money for another vehicle or engine then. I never got any knocking and engine still ran fine when I pulled it.

I did teardown the engine because I was curious. Rod, main and camshaft bearings had heavy wear. Measured 4-5 thousands clearance on main and rods. The pump was actually the one with minimal wear.

So except for the AFM lifter actuation (or however they work?), the engine may still run good with that oil pressure for a while if you don't have any knocking.

Next step: What are your capabilities mechanically, knowledge is and budget? Tools, time and space? That will dictate if you rebuild it yourself, have someone rebuild it, junkyard swap, crate engine, etc.

 

[Hoeston]

Hows she running now?

 

[Hoeston]

I recently changed my oil pressure sensor and the filter.
The check engine light had come on and oil pressure gauge stuck at max 80. 3 codes for the sensor failure.
Prior to changing the sensor/filter the gauge would idle around 30-35 when warm, closer to 40 when cold.
Now, after changing them, the gauge looks like 23-27 when warm, 36-40 cold.

Been wondering if this is the start of losing pressure

 

[Dustin Jackson]

@Hoeston Those sensors aren't calibrated for scientific accuracy so there will be variations between what the sensor reads, especially if going with non-factory oil pressure sensor

 

[j91z28d1]

I'd have to look it up again but the factory manual calls out low oil pressure something like 7psi hot idle. if you're at 20psi up to temp and idling at 600rpm you're doing better than most.

edit* plus all the dash gauges are kinda general. you really need a scanner to read the oil pressure as closely as you're trying to.

the water temp on the gauge center can be as much as 20deg different too and still show middle dash.

 

[2014PPV]

Hows she running now?

It's still going but the oil pressure is low—20 on startup and 12 after warmup ( 10-30w with Lucus.) Im not sure what route to go at this point. I have a low milage 4.7 from a 2005 but Im not sure how difficult, or costly the swap would be. It would be over my head so I would have to farm it out.

Hows she running now?

 

[Trey Hardy]

It's still going but the oil pressure is low—20 on startup and 12 after warmup ( 10-30w with Lucus.) Im not sure what route to go at this point. I have a low milage 4.7 from a 2005 but Im not sure how difficult, or costly the swap would be. It would be over my head so I would have to farm it out.

Do you hear any lifter tapping? If not it’s probably just a faulty sensor a possible solution for a more accurate reading is to add a mechanical oil pressure gage separate form the one on the gauge cluster for a more accurate reading possibly? Idk just throwing it out there I went through 3 sensors on my Tahoe and finally got sick of changing screens and or sensors when the last one went out I said f it and if I don’t hear no tapping I’m gunna send that biotch

 

[West 1]

Is the engine quiet as it runs? If it runs quiet, keep good oil in it and enjoy it till it wears out. I would consider using regular oil, not synthetic, I know all the synthetic advantages but one they do not talk about is synthetic will flow more or leak more as the engine runs. It is thinner when hot and will pass through holes that regular oil will not. So it is very good but not for all things. Petroleum based might raise your pressure up a tad. I would also switch to a 10-40 to help plug your internal leaks. If it starts and runs quietly keep running it, you might get another 75,000 miles before something fails.

 

[Charlie207]

Worn cam bearings, and leaking AFM/VLOM o-ring seals will lower pressure.