fnmadog

08' Express 3500 6.0L 22K Miles (bought it from an auction)
Oil pressure is running a little low.

40 psi at start
29/30 at warm idle
39/40 at high cruising speed

never goes below 29 ish. Engine feels strong, accelerates fines, idles fine, drives fine.. just the oil psi is low at idle and it bugs the heck out me...

I'll be picking up a gauge tuesday to check psi, bypassing the sender unit. (crossing my fingers it's that...)
If that's not it then maybe replace the oil pump... but i don't think that's it.
I'm mentally preparing for worn bearing or something else requiring a overhaul...

My question.
Is this normal for these engines?
Is it safe to drive this engine with a slightly low oil pressure? or am I putting something else at risk?
If i can drive it safely, any guess how many miles i'll get on it before it kicks the bucket and stops creating pressure?
Anyone have these symptoms, if so what was it?

Thanks for any advice and info!

canucklehead

What oil are you running?

fnmadog

5w-30

payed more attention to it yesterday.

22psi at idle when it's completely warmed up.

also seen that the voltage is at about 12/13 on the gauge.

and also noticed the a/c gets warmer when it's at idle, ice cold when cruising though.

not sure if all those could be related.. service belt seems to be at the right tightness.

CADru

'09 Express 6.0L 95K miles.
At warm idle (500 RPM): gauge reads 22
High speed (3000 RPM): gauge reads 40
I assume pressure would fluctuate relative to engine RPM. Never drops below 20 at warm idle.

canucklehead

Voltage will float around 12 to 13 when full charged.....but if you leave the door open for an hour then start it it should be at 14......
A/C not as cold at idle is a sign of low refrigerant.....run it till its notciably less cool at cruise......however don't run it without ref....as that will mess up the compressor....get it recharged......since the comp runs with defrost selected....

fnmadog

thanks for info

@CADru - has your engine always done that?

I'm used to engines sitting at 40 psi, then only going up when it under acceleration, not going under 40.

Thanks again!

CADru

Yes. And I believe the oil pressure would be in the 20-30 range at low RPM. Assuming you have correct amount of oil. To much oil would probably cause higher pressures and poor acceleration. But I'm not a an auto/engine mechanic. Though I'm not big fan of "idiot" gauges.

fnmadog

pretty much the same here. i understand enough to know i don't know enough... but i have no problems getting dirty.

as i read more and more, it seems these and other chevy engines run around the same, but i can't get a perfect psi from anything official. some people say gm won't even service them unless they get under 6psi per 1krpm. also read that the engines that run with a lower psi (25psi ~) don't consume as much oil. interesting but i don't know if there is any fact to it.

my oil is good, between 4 and 5 dot on the dip stick, with the correct oil.

as for now i've got new tires and my breaks are good, everything is safe to drive and use and seems to be running strong. i'll just run it and watch it until it goes below that psi or stops working.

CADru

And saving a Buck on outrageous labor costs! Checked again and when engine cold it's at 40 Pei. Makes sense cause would be at low viscosity. As engine warms the pressure would decrease. So is you have correct amount of oil and proper weight you should be OK. When the low pressure light comes on then you know you have a problem. I think the light would illuminate even if gauge indicates a higher pressure. I run Mobil super high mileage 5W30.

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2009 Express 2500 6.0L

CADru

I mean HIGHER (thicker) viscosity when cold...