Post your “ cold start “ oil pressure and oil details.

[Snagglefoot]

Just one thing. What was the air temp during these “cold starts”? Mine was -4 F.

 

[LouC]

Lots of things in motion here. I don’t suppose you started your boat engine at -4F? What I see is that the oil viscosity gets bizarre at -20 C ( -4 F ). People hand ring over a 2 cSt vs a 16 cSt oil at 100 C. Try 50,000 cSt at -20 C.

No but our 2 other vehicles that have oil pressure gauge/read out have been started at zero degrees F and they don’t do what you’re seeing. That doesn’t mean what yours does is abnormal though. Ever ask on Chevy truck forums?

 

[Snagglefoot]

The LS forums confirm around 40 to 42 psi on the highway, ( except for the variable pump speed ones with a solenoid in recent years, which bump the oil pressure during acceleration. )

Idling pressure just below 40 psi is considered normal.

Folks would be concerned about 20 psi. I doubt though, that anyone tracked pressures at very low temps.

The grandpa rule of 10 psi per 1000 rpm is a bit old because these engines with their multiple overdrive ratios can cruise at 65 mph at 2100 RPM and 42 psi. The truck is in my heated garage now and tomorrow’s start will be at 60 F. I’ll report back. Thanks for all the input.

 

[andreigbs]

My '22 EcoD will sit at just about 80psi from dead cold, and will be at or a bit above 20psi at hot idle.

 

[14Accent]

My 250k+ mile 4.7 WJ reads 70 PSI at cold start, 55-60 PSI at 2k RPM hot, 40-45 PSI at hot idle. The factory bypass pressure is 75 PSI.

I run whatever oil I feel like at the time of service. I think right now it's got 5w30 high mileage in the sump. I've run 10w30 with more or less the same pressure readings.

 

[KrisZ]

Pentastar with its dual speed oil pump behaves nothing like a traditional oil pump.

This is typically how it looks like, doesn’t even have to be that cold for the pressure to be in the 80s and 90s.

 

[Thermo1223]

Pentastar with its dual speed oil pump behaves nothing like a traditional oil pump.

This is typically how it looks like, doesn’t even have to be that cold for the pressure to be in the 80s and 90

Same for the truck, it climbs to 87Psi on any cold start. It obviously gets off high pressure faster in the summer.

 

[OVERKILL]

Cold start on the SRT, with the sensor also at the top of the engine (it's above the timing cover), it quickly kisses the relief on the pump, which is 65psi. I'm sure you recall my thread on it:

Cold start oil pressure - the flow discussion

I'm going to start this with a video, please ignore the dust. This is a true cold start, vehicle has been sitting 24hrs, it was -18C overnight (-0.5F), was -14C at the time of the video (7F). Interesting artifact in that oil temperature doesn't register at this temperature, but did on a...

bobistheoilguy.com

I agree with @redhat that you've likely got a pickup o-ring issue.

 

[BigJakeChevy]

I thought this might interesting during the current cold snap.

I started my 2008 Chev 6.0 LS engine at -4 F and got around 20 psi indicated on the pressure gage. Once fully warm at 200 F on the water temp gage, it was idling at just under 40 psi. The oil is Pennzoil Platinum Euro 5w40. The oil pressure gage is high up on the engine and monitors the oil pressure after it goes through the filter and climbs up the oil galleys to the top of the engine.

View attachment 131647 View attachment 131648

This is what was happening in mine right before the oring on the pickup tube failed. When the oring was cold it wouldn’t seal and after it warmed up it would seal and return to proper oil pressure.

 

[BigJakeChevy]

@Snagglefoot Looks like you could use a new pickup tube o-ring. Very common on Gen III and Gen IV LSx motors. With time, the seal shrinks and hardens. Upon startup, lower pressure. After some run time, the o-ring swells from heat and the oil and expands. A common test for this is to jack the rear of the motor up and overfill the engine to effectively submerge the pickup tube/pump joint in oil -- if the pressure if higher, then you know that o-ring needs replacing.

On my 2005 Suburban, it was hard as a rock, and I'd have 30psi at cold start -- it wouldn't budge with RPM much until it would warm up. Now, a cold start is 55psi with hot idle anywhere from 38-42psi.

Same as mine. When I changed the oring I could see marks were the oil was washing past the oring.

 

[nicholas]

I can’t say that I’ve ever seen that behavior. Oil pressure should peg and be highest at cold start.

Dropping so low seems odd too because I’d expect that any mechanical bypass would close long before that.

That gauge may wel be buffered or not real.

The only delays I see are on my Cummins trucks where the filters don’t stay full for whatever reason, so it takes a second to pump up, or similarly on the mechanical gauges on my MB diesels which have a pipe that needs to be pumped up. And that’s like a second. Then pegged. They’ll drop when the oil is warm.

Here’s an example of the gauge pumping up after sitting for five months. Usually it’s much faster.



Here’s my high mileage Cummins after I got it. With two mismatched old batteries. You can see the oil pressure build up because the filters drain back about 1/3.

Every engine I have had displayed the opposite.
High psi when cold and lower as the engine warms up.
Oil is much thicker when cold.
What gives ?

 

[nicholas]

The positioning of the oil pressure sensor is important to interpreting results. Here is the diagram for the oil system on a LS engine. Oil enters the pump at the front of the engine, travels the length of the block, goes through the oil filter then climbs the height of the block where the sensor is exposed to the flow of the oil. The oil then travels through the galleys to the cam and lifters and down to the main bearings while some goes up into the heads and lubricates the rockers and valve stems.

View attachment 131653

It's still cold very thick oil.....something is up?

 

[BigJakeChevy]

Every engine I have had displayed the opposite.
High psi when cold and lower as the engine warms up.
Oil is much thicker when cold.
What gives ?

Bad oring on pickup tube. They harden in time. So when cold they leak causing low pressure once warm the seal up and normal pressure resumes

 

[nicholas]

Bad oring on pickup tube. They harden in time. So when cold they leak causing low pressure once warm the seal up and normal pressure resumes

Did the OP find this was their issue?
Interesting

 

[Snagglefoot]

Did the OP find this was their issue?
Interesting

The temps have since risen and the problem went away. Because it’s a 4 wheel drive it’s a major pain to drop the pan to change the O ring. I’ll monitor the situation and see if I get any other indications of problems.

 

[JHZR2]

Every engine I have had displayed the opposite.
High psi when cold and lower as the engine warms up.
Oil is much thicker when cold.
What gives ?

Not sure I get your point. I think we’re saying the same thing. High when cold, then drops when warm…

 

[nicholas]

Not sure I get your point. I think we’re saying the same thing. High when cold, then drops when warm…

Yes.....
I am also offering my observations as well.

 

[gman2304]

Bad oring on pickup tube. They harden in time. So when cold they leak causing low pressure once warm the seal up and normal pressure resumes

^ My 2005 Chevy 5.3 w 235,000 miles was showing the same symptoms as the OP‘S, low oil pressure at cold start. A new oil pump pick up O ring fixed the problem.

 

[LouC]

Glad the cause was found and the solution is a well known one. My 07 Jeep 5.7 doesn’t have a gauge so I hooked up my fancy new Autel scanner to it to measure pressures.
Cold start approx 45-55 psi dep on RPM
Hot idle 20-25 psi
Checking on various Mopar boards these are typical.
This is running Mobil 1 5w/20.

 

[BigJakeChevy]

The temps have since risen and the problem went away. Because it’s a 4 wheel drive it’s a major pain to drop the pan to change the O ring. I’ll monitor the situation and see if I get any other indications of problems.

Hey man, honestly it’s not that bad. Mine was on an 07 classic so i had to disconnect the pitman and idler arms but removing the diff and starter were all that bad. Well worth it to save an engine.