What does your oil pressure run at? Cold vs. fully up to temp?

Maxxarcade · Oct 25, 2020

I have a 2011 Tahoe with the 5.3. Currently 185k miles. When I got it, it was giving codes for low oil pressure. I had a dealership replace the oil pump, relief valve, and o-rings. It also has a new pressure sender and filter screen.

Even with the new parts, the highest I've ever seen the pressure go was a bit over 40 psi. And that is while accelerating after a cold start. It then hangs around 20 when driving, with temp reading 210. But after about 20 more minutes it will be all the way down to what looks like 5-6 psi at idle, and won't go above 20-30, even at higher RPM.

I started using a Range AFM disabler shortly after the repairs were done, and haven't had any more error codes or check engine light, and it's been over a year. But the pressure just seems really low to me. The dealership says it's within spec though?

This is a pic of what my gauge reads at a stop light after driving for about 20 minutes. This was taken 5k miles ago, and it's still the same now.

What does yours read when it's at it's lowest point?

camaroz2887 · Oct 25, 2020

Have you checked the actual oil pressure reading? I’m not sure for these particular trucks but some vehicles have a dummy gauge that’ll show weird reading but be fine until it actually drops too low and sets off the bells and whistles.

That’s low enough to get me worried. No new codes or warnings?

Maxxarcade · Oct 25, 2020

The dealership said it was within spec. Though I'm not sure how long they left it running at full operating temp when they tested it. Even after fully warming up, it still takes a bit of driving before the pressure drops. It's like the oil keeps getting thinner over time, even though the temp stays at 210.

I haven't had any more codes or warnings, and I've put about 7,500 miles on it since I got it. I used to get occasional "catalyst below threshold" codes, but those went away after I started using the AFM disabler.

iamdub · Oct 25, 2020

Maxxarcade said:
The dealership said it was within spec. Though I'm not sure how long they left it running at full operating temp when they tested it. Even after fully warming up, it still takes a bit of driving before the pressure drops. It's like the oil keeps getting thinner over time, even though the temp stays at 210.

I haven't had any more codes or warnings, and I've put about 7,500 miles on it since I got it. I used to get occasional "catalyst below threshold" codes, but those went away after I started using the AFM disabler.

Mine was around 27-30ish at hot idle and 40-43ish highway cruising. I'm guessing about 10psi higher when cold. It was always that way since I bought it with 147K and until I refreshed the engine at 200K.

Assuming the dealership confirmed the pressure with a mechanical gauge, I'd say you've ruled out all the usual suspects with all of the work already done. If you wanna throw one more part at it, replace the VLOM and gasket.

BTW, the dealership would go by GM's specs, not "their" specs. I, and may others would disagree with at least a few of GM's specs. For example, they don't consider an engine as having an oil consumption issue unless it burns more than one quart per 2,000 miles. Anything less is "within spec".

Joseph Garcia · Oct 25, 2020

My 6.2 with 145k on it has ~50psi when cold. When warm, 40+ psi while driving at 1500 or more rpms, and ~20psi at idle.

swathdiver · Oct 25, 2020

Maxxarcade said:
I have a 2011 Tahoe with the 5.3. Currently 185k miles. When I got it, it was giving codes for low oil pressure. I had a dealership replace the oil pump, relief valve, and o-rings. It also has a new pressure sender and filter screen.

Even with the new parts, the highest I've ever seen the pressure go was a bit over 40 psi. And that is while accelerating after a cold start. It then hangs around 20 when driving, with temp reading 210. But after about 20 more minutes it will be all the way down to what looks like 5-6 psi at idle, and won't go above 20-30, even at higher RPM.

I started using a Range AFM disabler shortly after the repairs were done, and haven't had any more error codes or check engine light, and it's been over a year. But the pressure just seems really low to me. The dealership says it's within spec though?

This is a pic of what my gauge reads at a stop light after driving for about 20 minutes. This was taken 5k miles ago, and it's still the same now.

What does yours read when it's at it's lowest point?

View attachment 260911

Aaron, do you have an LMG or LC9 engine? Put two extra quarts in the motor and let it idle up to temp, you can even drive around without hurting anything. If the pressure stays up, it's the o-ring in the pick up tube. If the pressure is still low, then there's a problem somewhere. Probably worn camshaft bearings and for that you have to pull the motor. There is also a relief valve in the oil pan that can bleed off pressure and if the VLOM o-rings begin to fail, those too can bleed off oil pressure and of course cause lifter problems. Your least expensive repairs are the pick up tube o-ring and relief valve, then the VLOM, then the cam bearings.

Maxxarcade · Oct 25, 2020

I think it's an LMG but I'd have to double check.

The pick-up O-ring got changed when the oil pump was replaced. Same for the relief valve.

This is actually an SSV model that was used by a local police dept. The service records show that the camshaft was replaced at 103k miles. Hopefully it's not the bearings.

What bugs me the most, is that I paid $2k to have the repairs done, and the dealership thinks everything is fine despite the pressure being obviously low. And they act like they've never seen the common issues on these engines.

swathdiver · Oct 25, 2020

Maxxarcade said:
I think it's an LMG but I'd have to double check.

The pick-up O-ring got changed when the oil pump was replaced. Same for the relief valve.

This is actually an SSV model that was used by a local police dept. The service records show that the camshaft was replaced at 103k miles. Hopefully it's not the bearings.

What bugs me the most, is that I paid $2k to have the repairs done, and the dealership thinks everything is fine despite the pressure being obviously low. And they act like they've never seen the common issues on these engines.

Ok, the motor is an LMG and what probably happened is that a lifter broke and took out the camshaft. With the work that was done you are left with two likely culprits, the VLOM and the cam bearings. The VLOM should have been replaced with the latest model when the work was done. I am assuming that they did not delete AFM.

There are 8 o-rings between the VLOM and block and if they begin to leak, they'll bleed off pressure but I do not remember when; like, if AFM is active or not or if it matters. @iamdub

Yeah, the manual says 6 psi at idle is fine, would scare me still though!

iamdub · Oct 25, 2020

swathdiver said:
Ok, the motor is an LMG and what probably happened is that a lifter broke and took out the camshaft. With the work that was done you are left with two likely culprits, the VLOM and the cam bearings. The VLOM should have been replaced with the latest model when the work was done. I am assuming that they did not delete AFM.

There are 8 o-rings between the VLOM and block and if they begin to leak, they'll bleed off pressure but I do not remember when; like, if AFM is active or not or if it matters. @iamdub

Yeah, the manual says 6 psi at idle is fine, would scare me still though!

I think leaking VLOM O-rings could bleed off pressure at any time, but worse when under pressure when the VLOM solenoids are closed. The solenoids closed would be to pump up the lifters, so this would be when AFM is not active. This happens always at idle and at probably something like 95% of any other time during driving.

The oil galleys are pressurized and so are the towers, and those O-rings are at the tops of the towers, sandwiched between the tower and VLOM. They'd have to be leaking pretty badly to cause such a drop in pressure. Since it's a PPV, it likely did a LOT of idling. Low oil psi at idle for extended periods may have caused accelerated lifter and/or cam lobe and/or cam bearing wear. Maybe it already had a failure and the cam (and probably lifters) were replaced but they skimped on pulling and disassembling the motor to have the cam bearings replaced.

iamdub · Oct 25, 2020

Maxxarcade said:
I think it's an LMG but I'd have to double check.

The pick-up O-ring got changed when the oil pump was replaced. Same for the relief valve.

This is actually an SSV model that was used by a local police dept. The service records show that the camshaft was replaced at 103k miles. Hopefully it's not the bearings.

What bugs me the most, is that I paid $2k to have the repairs done, and the dealership thinks everything is fine despite the pressure being obviously low. And they act like they've never seen the common issues on these engines.

You could run a heavier oil to get the pressure up enough to keep the codes from setting. I like 15W-40 Rotella. If you don't wanna run Diesel oil, try 20W-50. If you feel that's too heavy, run 3-4 quarts of it thinned down a little with 2-3 quarts of the same brand and type but lighter weight.

What does your oil pressure run at? Cold vs. fully up to temp?

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