Oil pressure slow to build at startup

[Matthew Jeschke]

Okay, so I thought I had a post on this somewhere but cannot find it. My 2001 Z71 Tahoe is at nearly 240,000 miles. I bout at 225,000 miles. Has 5.3L v8. I'm wanting to swap out for a 6.0L and hoping this motor holds together until then. It's had some minor annoyances but this is the only one that concerns me...

I'm running 5w-30 oil and is pretty hot where I live.

1. I start up the truck... after which it takes a little while to build oil pressure. Oil pressure fluctuates a bit as well once idling. But seems to maintain a good pressure.

2. I turn off truck and wait about 30 seconds... then restart it. Same symptoms persist, leading me to believe block is quickly bleeding oil pressure somewhere.

I thought might be a bad oil filter / drain back valve so I bought a Wix filter and swapped it on but seems to continue to have same problem.

I'm wondering if this might be a sign of heavily warn main bearings.

 

[rockola1971]

oring at your oil pickup tube in the pan.

 

[Matthew Jeschke]

And like an idiot I redid oil pan gasket but not that :/

I doesn't seem to be too bad right now though but maybe you can tell from this video...

Ps, can that pickup tube gaske be changed by removing front cover?

Sent from my SM-G925V using Tapatalk

 

[SnowDrifter]

Can you read live data or check with mechanical gauge? Honestly that just looks like normal gauge behavior to me. If memory serves, that year has an air core stepper motor, which is prone to clogging / lubrication failure with age. It's not an encoder like the later trucks. Hence why I question if it's a real concern or one of gauges.

As far as bleed off: there's no air, accumulator, or other source of elasticity in the lubrication system other than the small amount offered by the irom block, steel filter housing, and maybe some flex on the rear cover. But at the pressures these are at, those are negligible. The short answer is oil Pressure is related to engine rpm with essentially no delay once the system is primed and full. Engine turns off? Oil Pressure gone in an instant. Rev to 5k? There's full oil Pressure immediately

 

[SnowDrifter]

Also, yes you can get to the gasket by removing only the front cover but it's not my chosen route. You might have to trim / bend a wrench, and do NOT drop that bolt or you'll be ripping pan off anyway

 

[Matthew Jeschke]

Can you read live data or check with mechanical gauge? Honestly that just looks like normal gauge behavior to me. If memory serves, that year has an air core stepper motor, which is prone to clogging / lubrication failure with age. It's not an encoder like the later trucks. Hence why I question if it's a real concern or one of gauges.

As far as bleed off: there's no air, accumulator, or other source of elasticity in the lubrication system other than the small amount offered by the irom block, steel filter housing, and maybe some flex on the rear cover. But at the pressures these are at, those are negligible. The short answer is oil Pressure is related to engine rpm with essentially no delay once the system is primed and full. Engine turns off? Oil Pressure gone in an instant. Rev to 5k? There's full oil Pressure immediately

I have a scan tool with live data. However better like your mechanical reader.

Although, maybe i am fine if that looks like standard behavior.

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[Rocket Man]

It looks normal to me. I see nothing to worry about.

 

[HiHoeSilver]

Mine acts exactly the same as your video.

 

[Chris2144]

Mine primes just a hair quicker than yours but I also only have 170k miles. Mine also is a little twitchy at idle. And every GMT 800 I've owned is that way. Like what had already been stated I think you're fine but the pick up gasket is common on these so keep that in mind

 

[SnowDrifter]

For what it's worth

@62f ambient

 

[SnowDrifter]

edit: Double post