Another oil pressure issue

[RustedHoe04]

So here is the skinny. 04 Tahoe, 5.3. Has 297k on the clock. Recently replaced oil pressure sending unit(posted pic of what under the sending unit looks like, could not see screen, horrible placement for sending unit). Replaced pick up tube oring, new oil pump, timing components, all associated gaskets, timing cover, water pump, oil pan, timing cover seal. On start up in the morning, it holds 20psi. After oil warms up, at idle, 5PSI. 65 mph-38psi, all according to the dash gauge. Debating on running a pressure gauge(Equus brand). I have seen there is a plate that bolts on the oil pan, next to the oil filter. Has anyone installed one of these on their Tahoe? Also developed the lifter tick after last oil change. Trying to see why the oil pressure was low, l held the RPMs at 2000, heard a puff of air, and the tick started. Any pics of your set up is appreciated. Just trying to make this thing trustworthy again. Taking a 3 hour trip in October and want to have the extra room, wife’s Kia is too small.

Side note, I have a non Flex fuel, and got a code for a P0178 recently. Says it’s a flex fuel issue…‍. Thanks for the info in advance. Much appreciation.

 

[afpj]

Did you use a sending unit with a screen? GMT 800s don't use a screen for the sending unit.

 

[West 1]

At 300,000 miles you may be up against worn out parts? The Cam Bearings wear and as they get loose you will lose oil pressure leaking from the cam bearings. Rod and Main bearings can wear also and increase leaks which drop oil pressure. If trying a new oil pump to fix low oil pressure always install a High Volume Pump. Melling offers one. The High Volume pumps can flow more oil which can mask internal leaks within reason. Based on your running oil pressure compared to idle oil pressure this is the most likely issue in your engine. Installing a High Pressure pump would not help at all. The engine will not build pressure until it is flowing more oil than all the oil galleries need. With internal leaks the pump can’t put out enough flow to build pressure until you raise the RPM which gives more flow and pressure builds. My 2008 6.2L engine with 145,000 miles has 60 psi above 1500 RPM but only 20 psi hot idle. Tells me something is loose inside, Cam, Rod or Main Bearings probably but it is a good engine and there is no reason to try and repair it. Even at 7 psi at Hot idle the engine will live, we just don’t like that.

 

[RustedHoe04]

At 300,000 miles you may be up against worn out parts? The Cam Bearings wear and as they get loose you will lose oil pressure leaking from the cam bearings. Rod and Main bearings can wear also and increase leaks which drop oil pressure. If trying a new oil pump to fix low oil pressure always install a High Volume Pump. Melling offers one. The High Volume pumps can flow more oil which can mask internal leaks within reason. Based on your running oil pressure compared to idle oil pressure this is the most likely issue in your engine. Installing a High Pressure pump would not help at all. The engine will not build pressure until it is flowing more oil than all the oil galleries need. With internal leaks the pump can’t put out enough flow to build pressure until you raise the RPM which gives more flow and pressure builds. My 2008 6.2L engine with 145,000 miles has 60 psi above 1500 RPM but only 20 psi hot idle. Tells me something is loose inside, Cam, Rod or Main Bearings probably but it is a good engine and there is no reason to try and repair it. Even at 7 psi at Hot idle the engine will live, we just don’t like that.

I did install a melling 295HV. I checked the rod bearings when I took the belly pan off, didn’t have any significant play, caps had very little side to side, if any at all. I am in this feel that it’s either my dash cluster is off, like the cluster motor is failing, or I might have an oil passage sludge blocked. I did run a can of Berrymans in this oil change, and i plan on changing again soon. I don’t run that stuff in oil much past 1000 miles, kinda like running ATF. I am giving serious debate on just buying a used 5.3 and rebuilding it, just in case this one is in process of motor death. I haven’t pulled the drivers valve cover yet to check the rockers and push rods, checked passenger side, the rocker arms have a little side to side play, but none were loose. Checked torque specks, all tight. I cleaned out the push rods by soaking them in Seafoam for a day. This one just has me a little stumped.

 

[Marky Dissod]

... giving serious debate on just buying a used
6.0L
and rebuilding it, just in case ...

Fixed it for you.

Instead of more caustic engine flush-type stuff,
have you considered Valvoline Restore & Protect 5W30?
Or are you running with a thicker oil, say, 10W40?

 

[RustedHoe04]

Fixed it for you.

Instead of more caustic engine flush-type stuff,
have you considered Valvoline Restore & Protect 5W30?
Or are you running with a thicker oil, say, 10W40?

Next oil change I am gonna run a 10w40. Have about 250 miles left. This condition came up out of the blue. Looking at Liquid Moly products. Yeah, they are expensive, but if it saves me issues for a few months until I can get the new to me motor rebuilt, I will be happy.

 

[RustedHoe04]

Fixed it for you.

Instead of more caustic engine flush-type stuff,
have you considered Valvoline Restore & Protect 5W30?
Or are you running with a thicker oil, say, 10W40?

I just saw the used 6.0, that is great bro. If I find a deal on one, will definitely make it an option. Not looked into what it takes to do the switch

 

[Marky Dissod]

I just saw the used 6.0L, that is great bro. If I find a deal on one, will definitely make it an option. Not looked into what it takes to do the switch.

Physically, there are no meaningful physical differences between any 4.8L / 5.3L / 5.7L / 6.0L / 6.2L / 7.0L that prevent them from being physically interchangeable.
That's the whole gottdamnt point - if you can't read, then nearly all their differences become parts swapping issues.

Which leads me to my next point:
if you get an LQ4, or any other 6.0L with dished pistons, or pistons with valve reliefs,
just use the Gen3 5.3L holy port heads (61cc chambers).
if you get an LQ9, or any other 6.0L with flat pistons,
then use the Gen4 5.3L holy port heads (65cc chambers).

Then all you need is a competent tuner. That's all, folks.

 

[rdezs]

Excellent advice above. I personally wouldn't throw any more parts at it.... I'd start putting a plan together on either a rebuild or replacement engine. Meanwhile, I would do an oil change with a 10w40 full synthetic. At 300K, that should help with the excess bearing clearances which would be expected.

 

[RustedHoe04]

Appreciate all the advice!