I'll be changing the oil pump on my 08 Silverado 4.8, seems there is no oil pressure at low idle. I might as well change the timing chain, tensioner and gears while I am right there. This post just shows, it won't be like it was in the 70s. Looks like I will be taking a nice weekend to take my time to do this job.
4.8L Low oil pressure
- Thread starter gmonly
- Start date
Mooseman
Moderator
Totally different engine. It's almost like the 70's on the LS engines except you have to drop the oil pan for the oil pump unless you cheat like I've talked about:
gmtnation.com
how to remove oil pickup tube bolt??
I give up. Is there a secret to removing the oil pickup tube bolt from the oil pump without loosening or removing the oil pan? I can't for the life of me figure out how to access it. Why GM would use the bolt hole they did and not the other threaded hole in the pump like Corvette uses.
gmtnation.com
@gmonly ...These Videos cover another issue with Low Oil Pressure Readings in the 4.8L, 5.3L and 6.0L LS Motors having the Oil Pressure Sensors Screens/Filters becoming Sludged Up.
There is a Special Oil Pressure Sensor Socket that is a MUST to get over the Damned Oddly Shaped Hex Head with Rounded Corners and then be able to use either a Pick (Or by Threading in a Long 10MM Bolt to Pull Out and Extract the Clogged Up Black Plastic with S/S Screen Filter Basket within.
Then Lube the Plastic Body and Slide in the Brand New (or CLEANED UP) Old Filter Basket right back Inside followed by the New Oil Pressure Sensor with its OEM Thread Sealer right back into that Hidden Port.
While also being a Basic PITA to R&R this Sensor & Filter Basket... if done first... And should your Oil Pressure Return to Nominal... Then you may NOT need to R&R the Oil Pump and Clean the Oil Pump Pick Up Tube in the Engine Bottom End:
Good Luck!
There is a Special Oil Pressure Sensor Socket that is a MUST to get over the Damned Oddly Shaped Hex Head with Rounded Corners and then be able to use either a Pick (Or by Threading in a Long 10MM Bolt to Pull Out and Extract the Clogged Up Black Plastic with S/S Screen Filter Basket within.
Then Lube the Plastic Body and Slide in the Brand New (or CLEANED UP) Old Filter Basket right back Inside followed by the New Oil Pressure Sensor with its OEM Thread Sealer right back into that Hidden Port.
While also being a Basic PITA to R&R this Sensor & Filter Basket... if done first... And should your Oil Pressure Return to Nominal... Then you may NOT need to R&R the Oil Pump and Clean the Oil Pump Pick Up Tube in the Engine Bottom End:
Good Luck!
Last edited:
The problem is, I already changed the Screens and sensor 2 times, thinking I bought a bad one, I do have the socket, worked in a garage for 50 years, you tend to buy a lot of tools. I use a pic for removing the screen basket, a little tight with big hands. After changing it 2 times, and still no oil pressure, I would say the pump needs attention.
Mooseman
Moderator
The 4.8 does not have the screen under the sensor since it does not have DOD/AFM. If you put one in there, I would strongly suggest you take it out.
And before diving into an oil pump swap, I would check oil pressure with a mechanical gauge. If an oil change to a higher viscosity oil seems to improve the pressure, I would suspect more worn bearings. In that case, you could improve oil pressure by installing a high volume and pressure pump. It's a crutch for worn engines but can help extend its life.
And before diving into an oil pump swap, I would check oil pressure with a mechanical gauge. If an oil change to a higher viscosity oil seems to improve the pressure, I would suspect more worn bearings. In that case, you could improve oil pressure by installing a high volume and pressure pump. It's a crutch for worn engines but can help extend its life.
Mooseman
Moderator
Agreed with @Mooseman above. Check with a mechanical gauge before going further. All the other bases have been covered it appears above.
Im assuming you have a bi-directional scanner to see if their is actual oil pressure sense making it so the ECM can see it? The reason is, the gauge cluster is very prone to failure, and its just the gauge that tells the cluster to say "low oil pressure", not the ECM.
Im assuming you have a bi-directional scanner to see if their is actual oil pressure sense making it so the ECM can see it? The reason is, the gauge cluster is very prone to failure, and its just the gauge that tells the cluster to say "low oil pressure", not the ECM.
What gage, the 08 1500 did not have a gage, it only goes into limp mode, the reader/writer shows there is low oil pressure
The manual shows there is a screen in there, the auto parts stores show there is a screen in there, I took one out when I changed the sensor the first time.
2008 Silverado 4.8 engines do have a screen under the oil pressure sensor. This screen, also known as an oil pressure switch filter, is designed to prevent debris from obstructing the oil flow to the engine's components. It's located on the back side of the engine, underneath the intake.
Mooseman
Moderator
I know exactly what you're talking about. I've done a DOD/AFM delete on a 5.3 using a valley cover from a 4.8 and it does not use a filter under the oil pressure sensor. There's nowhere for that oil to go to get filtered. On a DOD/AFM engine, That filter prevents debris from going through the oil manifold (called a VLOM) and into the deactivating lifters.
Whereas the 4.8 lifter valley cover has none of that:
And just to make sure, I checked the parts listings on RA for the 4.8 and the 5.3, which does have AFM, the 4.8 does not list an oil pressure sender filter separately whereas the 5.3 does. Some of the senders however do include the filter as the sensor fits on both so on a 4.8, you would not use it.
Whereas the 4.8 lifter valley cover has none of that:
And just to make sure, I checked the parts listings on RA for the 4.8 and the 5.3, which does have AFM, the 4.8 does not list an oil pressure sender filter separately whereas the 5.3 does. Some of the senders however do include the filter as the sensor fits on both so on a 4.8, you would not use it.
Mooseman
Moderator
He's talking about putting a test gauge in the sensor port. Even then, the PCM is getting oil pressure sensor data and can be read using a capable scanner or a Bluetooth adapter and an app like Torque on an Android device to read it.
"The reason is, the gauge cluster is very prone to failure" this is what I was talking about. I have a 10-inch tablet code reader/writer that reads the temp and the pressure
Mooseman
Moderator
I think it was replaced in the past by someone that got one of those sensors with the filter and figured to put it in anyway even if there wasn't one in there originally. It could be the reason for the pressure reading problems. If you check the parts listings on RA, some have it, most don't. Looking at the list of vehicles that the sensor with the filter fits, it even lists TrailBlazers all the way from 2003, prior to DOD/AFM and this filter even ever existing. It's a case of parts included that are not required for all models, kinda like rebuild kits where there are gaskets that are used on some years but not others.
I took the screen back out, broke my left wrist doing it (slipped through the front end with my hand behind the intake) I think I will have to change the oil pump, it only happens now and then.
Mooseman
Moderator
This was also interesting...if you were running with an Over-Sized Oil Filter trying to get better filtration... FWIW... The sheer Physics involved here do make perfect sense, because:
"As Area INCREASES... Pressure Decreases..."
physics.stackexchange.com
"As Area INCREASES... Pressure Decreases..."
How does pressure of a fluid change with area, according to the continuity equation and Bernoulli's equation?
In a nozzle, the exit velocity increases as per continuity equation $Av=const$ as given by Bernoulli equation (incompressible fluid). Pressure is inversely proportional to velocity, so we have lower
physics.stackexchange.com
Last edited:
Mooseman
Moderator
I would be more inclined to think it's the new oil that bumped up the pressure on that one but worth a look. I know mine would go up on new oil.
I bought a digital pressure gage, I added an adaptor for both to be in the same port. I have yet to finish connecting it, and mounting it, I do have both sensors installed and the new wire ran. It is kind of hard to finish right now with my hand in a brace, and the hospital just tells you to take Tylenol for pain. I drove to the hospital and the truck ran well, no limp mode.
I have the oil filter called for by the manual, just different brand, one that I have always used, no oversized filter. In fact, it has the 5w30 oil that is required by GM for this truck engine, I used the 20w40 on all my other trucks, but stuck with the recommended for this truck.
