Low oil pressure on cold start and lifter tap, slowly rises to normal with engine temp

[Reecedakid03]

2009 Tahoe 5.3 Low oil pressure on cold start and lifter tap, slowly rises to normal with engine temps and tap also goes away.

Got a 2009 Tahoe 240k miles on it. Did an oil change the other day 15w-50 no issues but cold started it this morning (40f) and she was tapping loud and had barely above 20 psi on a cold start. I let it warm up and oil pressure went back to normal. Is this a pick up tube o ring or could it be another issue that doesn’t require pulling engine/diff? Im aware of the plastic barbell in the back of the block as well but can’t get to that as now now. Truck has a new rear main seal and cover too. Once warm out of gear it idles at 35 psi. I could just drain some of the 50 weight and throw some 5w30 in possibly too. Any help is appreciated.

 

[thefrey]

Is there any reason why you are running 15w50? Is this the first time you’ve ran this oil/has this happened before with this weight oil?

A cheap test many talk about here for the o-ring is parking on a steep incline or jacking up the rear of the truck and putting an extra 2-3 quarts in the crankcase then starting it. This will cover the o-ring/pickup tube. If you do this and it fixes your cold start psi (assuming it’s not oil weight related) then it’s most likely your o-ring. After the test you need to drain the extra out of the crankcase before you drive it again.

Chances are, if the o-ring hasn’t been changed ever, it’s flat, and possibly dried out/cracked and leaking air. This was my o-ring at 200k

You can do the job without dropping the diff. You disconnect the passenger side CV axle and drop the diff and support it with a floor jack. It allows you to get the pan off without taking the diff fully off

 

[Foggy]

15w50 is really a race oil intended for warm weather only..
No wonder why you have low pressure and noise at start up
If it's going to be 40* in your area, switch to a 5w30 or at least 5w40
if you think you need such a "thick" oil.. At least you'll get some
cold weather characteristics of the "5" weight on start up !!!!!

 

[Marky Dissod]

15w50 (seriously?! don't do that again) is only for when it's warm enough to be nekkid outside.
15whatever is somewhere between molasses and wax in cold weather.
Low oil pressure was because oil pump literally could not pump it.
Use 0w30 / 5w30 / 0w40 / 5w40 - or use a block heater next time.

 

[donjetman]

Interesting
my $ is if its either? or a coincidence?
its caused by the filter
not the oil viscosity

change the filter first to a different brand
if that doesn't fix it
then change the oil to 5w-XX or 0w-XX
and let us know

I use to run VR1 20w-50 in everything I owned and never had a problem.

 

[Marky Dissod]

change the filter first to a different brand
if that doesn't fix it, then change the oil to 5wXX or 0wXX and let us know

I use to run VR1 20w-50 in everything I owned and never had a problem.

But what filter did you run?

 

[donjetman]

But what filter did you run?

anything and everything

 

[Marky Dissod]

But what filter did you run?

anything and everything

OK, then which oil filter(s) would you recommend - besides that we ought to pretend that our engines are 6.0L so we can get the slightly larger one?

 

[West 1]

Normally running your 15-50W in winter would peg your oil pressure gauge at 80 pounds or so not remain at zero?

I tried 15-40W diesel oil in a 5.3L that had a cold start knock, the noise was quieter, oil pressure was about 5 psi high but cold start it had oil pressure instantly, did not fall off at all.
I change oils frequently, not real picky on brands. I prefer WIX filters but sometimes install even a Fram if they are available fast. On that engine after the 15-40 test I pulled the oil pump and increased the relief spring pressure, start up knock was gone, idle oil pressure was solid 60 psi with 5-30W oil. It had 135,000 miles at that time.

The thick oil will flow slowly so the lifter may tick for a bit but oil pressure should be very high not very low.

Not sure if a leaking pick up tube o ring would seal faster or slower with thick oil? I suspect faster. You have an odd one going on.

 

[Marky Dissod]

His initial oil pressure was low because 15w50 @ 40F is basically a molasses-wax too thick to flow through the oil pump and create meaningful pressure.
Once it warmed up enough to FLOW, it could create pressure.
Solution is 0w30 / 5w30 / 0w40 / 5w40, or a block heater (or both?).