Oil pump questions

[Tatman48]

first my vehicle is an 08 yukon xl denali 6.2. I noticed over the winter oil pressure was low and shut off engine came on. once it warmed up pressure was low but the turn engine light off never came on. Now, if I dont get in and start driving the shut engine off comes on. when driving pressure is under 40 even at highway speeds it is below 40. and when I stop at a light it drops to almost 0 but shut engine doesnt turn on. I am wondering the chances if the melling pump is bad, or if it is just that stupid pick up tube o-ring. but would hate to take it down that far and change o-ring only to have same issue after. vehicle has 170k. lie I said when driving I have pressure, but when at a light after first starting it it says to shut if off unless I shift to neutral and give it a little gas. I am willing to do the oil pump but if consensus is it doesnt need swapped I will just do o-ring. also when I changed pressure switch there was no filter under the sensor. should I install one?

 

[Glisella]

first my vehicle is an 08 yukon xl denali 6.2. I noticed over the winter oil pressure was low and shut off engine came on. once it warmed up pressure was low but the turn engine light off never came on. Now, if I dont get in and start driving the shut engine off comes on. when driving pressure is under 40 even at highway speeds it is below 40. and when I stop at a light it drops to almost 0 but shut engine doesnt turn on. I am wondering the chances if the melling pump is bad, or if it is just that stupid pick up tube o-ring. but would hate to take it down that far and change o-ring only to have same issue after. vehicle has 170k. lie I said when driving I have pressure, but when at a light after first starting it it says to shut if off unless I shift to neutral and give it a little gas. I am willing to do the oil pump but if consensus is it doesnt need swapped I will just do o-ring. also when I changed pressure switch there was no filter under the sensor. should I install one?

I have same year and engine, and the exact same thing started happening at 175K in winter. Changed the o ring and it went away...I'd put money on that.

 

[iamdub]

First, make sure the oil level is where it should be on the dipstick. Then, position the car on a steep slope with the front end aimed downward, nose-down into a ditch would work. If the oil pressure doesn't go up, then it's probably not the O-ring. You could overfill the oil by a quart and try the slope again to confirm. Don't drive with it overfilled for very long, drain that extra quart as soon as you can.

 

[Tatman48]

Pressure goes up when driving. Just not when sitting at a light for to long. Oil level is spot on.... once it is driven a while the pressure stays up high enough to keep it from warning to shut it off. I am going to try the oring. Hopefully that fixes it. I just don't want to have to tear it back down again to do pump if o-ring doesn't fix it

 

[Tatman48]

I have same year and engine, and the exact same thing started happening at 175K in winter. Changed the o ring and it went away...I'd put money on that.

May I ask which o-ring you used? I know there are a couple different ones

 

[Glisella]

May I ask which o-ring you used? I know there are a couple different ones

I bought from RockAuto, 35K miles so far and zero issues.

MAHLE B32790 Oil Pump Pickup Tube Gasket $ 1.68

 

[iamdub]

Pressure goes up when driving. Just not when sitting at a light for to long. Oil level is spot on.... once it is driven a while the pressure stays up high enough to keep it from warning to shut it off. I am going to try the oring. Hopefully that fixes it. I just don't want to have to tear it back down again to do pump if o-ring doesn't fix it

It's gonna go up when driving because the oil pump is spinning faster. This doesn't rule out a weak pump or leaking O-ring or partially clogged pickup or...

Why not perform a 15-second test to confirm or rule out the O-ring?

 

[Tatman48]

Awesome

I bought from RockAuto, 35K miles so far and zero issues.

MAHLE B32790 Oil Pump Pickup Tube Gasket $ 1.68

 

[kbuskill]

You didn't mention how many miles are on the truck/engine.

I always feel like if I'm that far into something (like already having the oil pan off to change the O-ring) it's cheap insurance to just replace the oil pump.

That's what I did... Mellings HV/HP oil pump, new O-ring, new LS2 timing chain and tensioner at the same time. I actually have "too much" oil pressure now... lol

 

[swathdiver]

First, make sure the oil level is where it should be on the dipstick. Then, position the car on a steep slope with the front end aimed downward, nose-down into a ditch would work. If the oil pressure doesn't go up, then it's probably not the O-ring. You could overfill the oil by a quart and try the slope again to confirm. Don't drive with it overfilled for very long, drain that extra quart as soon as you can.

I thought it was 2 quarts to check???

FYI: Aluminum LS V8s use the Melling M365.