“Low oil pressure” I’m stuck...

[CDLute138]

05 Tahoe.
210,000 on the odo.
New oil pump, pick up tube o-ring, OPS etc, etc.
Throws “low oil pressure” at idle and slowing, when I get on the gas (increase rpms) pressure builds as it should. I’ve been through the list and checked and rechecked to no avail...any ideas?? I’ve put a gauge on didn’t see it below 20 ever, (500-800rpms) which is low I know but from what I’ve read 6psi/1000rpm is in spec??


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[George B]

Did you replace the sensor?

 

[CDLute138]

Yes I did...been through the whole damn list lol


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[George B]

Yes I did...been through the whole damn list lol


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Ok, good. Didn’t see a list of what you did so I had to ask.

 

[afpj]

What brand sensor? These rigs don't like aftermarket for a lot of the sensors...knock sensors and oil pressure sender being on top of the list iirc. What oil filter are you using? I've read some people having lower oil pressure because of a crappy filter

 

[iamdub]

05 Tahoe.
210,000 on the odo.
New oil pump, pick up tube o-ring, OPS etc, etc.
Throws “low oil pressure” at idle and slowing, when I get on the gas (increase rpms) pressure builds as it should. I’ve been through the list and checked and rechecked to no avail...any ideas?? I’ve put a gauge on didn’t see it below 20 ever, (500-800rpms) which is low I know but from what I’ve read 6psi/1000rpm is in spec??


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20 psi at idle on a 200,000+ mile engine isn't so bad, if that is your actual pressure. The mechanical gauge you tested with could've been inaccurate. When you had the gauge on it and it showed 20 at minimum, did the "Low Oil Pressure" warning come on?

 

[YukonRog]

How did the inside look when you replaced the pump? Could it have a clogged "artery" somewhere? Maybe sump screen? I think it should be higher. My '05 Yukon has nearly 40 psi at idle. I also agree it may be a bad filter, seen that before. Did you change oil viscosity? Just throwin out ideas.

 

[CDLute138]

What brand sensor? These rigs don't like aftermarket for a lot of the sensors...knock sensors and oil pressure sender being on top of the list iirc. What oil filter are you using? I've read some people having lower oil pressure because of a crappy filter

Duralast for this go round of sensor replacement, this is the 3rd I’ve gone through, different parts places as well and at $60 a pop...ugh! Filter is K&N oil filter on the last 2 changes


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[CDLute138]

How did the inside look when you replaced the pump? Could it have a clogged "artery" somewhere? Maybe sump screen? I think it should be higher. My '05 Yukon has nearly 40 psi at idle. I also agree it may be a bad filter, seen that before. Did you change oil viscosity? Just throwin out ideas.

Inside looked good. When I replaced the pump I replaced the pick up tube o-ring and cleaned the screen, pan hell even the tube itself. I did not however change viscosity...


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[CDLute138]

20 psi at idle on a 200,000+ mile engine isn't so bad, if that is your actual pressure. The mechanical gauge you tested with could've been inaccurate. When you had the gauge on it and it showed 20 at minimum, did the "Low Oil Pressure" warning come on?

I was doubting my gauge as it felt like it didn’t seat right, I had the ops unhooked at the time as that’s where I was taking my reading from, I don’t have the right attachment yet to take it from the filter port, which I would’ve loved to do to see the difference from top and bottom ends


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[cam3439]

If the oil pump pickup tube o-ring was nicked during installation, then it could caused those issues. This assumes the correct o-ring size was installed. Different oil pumps/tubes call for different size o-rings.

 

[retiredsparky]

For an older engine, with higher clearances, increasing viscosity to a 10-30 oil is ok. Are you using 5-20 viscosity?

 

[Rocket Man]

You didn’t specify if the pressure was the same before you changed the oil pump. I can only assume you changed it because of low pressure? Was there any difference at all? I suggest sending an oil sample off to Blackstone Labs for analysis while you work on this issue, just to see how much wear is happening. Also like mentioned, there’s different o-rings so when you installed the pump are you sure you used the right one, and exactly what pump did you use? Melling has 3 different pumps for these engines and you should have gone with the high volume high pressure one I believe due to your mileage.

 

[CDLute138]

If the oil pump pickup tube o-ring was nicked during installation, then it could caused those issues. This assumes the correct o-ring size was installed. Different oil pumps/tubes call for different size o-rings.

I didn’t see any nicks but I won’t rule it out


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[CDLute138]

For an older engine, with higher clearances, increasing viscosity to a 10-30 oil is ok. Are you using 5-20 viscosity?

I am currently using 5-20, 10-30 wouldn’t be a bad route to go


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[CDLute138]

You didn’t specify if the pressure was the same before you changed the oil pump. I can only assume you changed it because of low pressure? Was there any difference at all? I suggest sending an oil sample off to Blackstone Labs for analysis while you work on this issue, just to see how much wear is happening. Also like mentioned, there’s different o-rings so when you installed the pump are you sure you used the right one, and exactly what pump did you use? Melling has 3 different pumps for these engines and you should have gone with the high volume high pressure one I believe due to your mileage.

Pressure was actually lower before changing the pump, it definitely went up. I am using a melling pump but can’t for the life of me remember if I bought the high flow, I’m gonna dig through my paperwork and see if I can find it...that may just be my solution...


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[iamdub]

If you can rule out anything malfunctioning, worn or damaged (sensor, O-ring, etc.), then the only other cause would be excessive bearing tolerances. Nothing you can do about that but rebuild or replace the short block. IMO, the pressure isn't low enough to go there yet. I'd focus on increasing the pressure just to keep the warnings off and not worry about it. First step is to quit using lizard piss, the 5W-20, as your lubricant. Use 10W-30 at a minimum. I use four quarts of 5W-40 and two of 15W-40 Rotella T6 in mine to give it more viscosity than 5 but not as heavy as 15.

Are you the original owner? Do you know if it has always had 5W-20 in it?