Oil Pressure Low At Idle

[PaulRV6]

I need some help/opinions here. Engine freshly rebuilt, runs good, new stock oil pump, oil pressure good when cold 60-70 psi, as oil warms up press drops to alarmingly low levels at idle. Using 10w-30 Castrol.
With 160-165 water, oil press. at 10-12 psi idle but at 180-185 water temp the oil press drops to about 6 psi at idle (using VDO mech gage of known calibration). I am also using the factory oil cooler. Everything is either new or been cleaned before re-assembly. I am also using the 1/8" copper gage line.
Is this a problem that I should be concerned about?
What is generally the cause for low oil pressure at idle (hot), pump gear/cover clearance, brg clear, etc.?

Thanks for your suggestions as this has me more than a little concerned.

paul

 

[PaulRV6]

ttt....please. Anyone got any ideas or suggestions on this one? I know there was a similar thread going about oil pressure the question was of a different nature.

paul

 

[Steve Wood]

Did you use a new cover or install one of the steel plates along with the new gears into your old cover? What was the end clearance on the gears? The clearance lash between the two gears and the wall clearance?


What were your rod and main bearing clearances? New cam bearings?

Torque the pick up tube down properly so it can not loosen and suck air?

Has it been low from the very beginning or did it change after a few miles of running?

 

[PaulRV6]

Steve,

Originally posted by Steve Wood
Did you use a new cover or install one of the steel plates along with the new gears into your old cover?
I bought new GM pump cover adapter/gear set, no steel plate.

What was the end clearance on the gears? The clearance lash between the two gears and the wall clearance?
I checked all clearances and were within GM specs, end clearance was set at .001" (before removing cover to fix oil leak) so not sure if it ended up with that.

What were your rod and main bearing clearances? New cam bearings?
These were all set and verified to .0015"-.0023"

Torque the pick up tube down properly so it can not loosen and suck air?
Used GM new pickup tube with gasket and torqued to factory specs.

Has it been low from the very beginning or did it change after a few miles of running?

It was 10-12 psi at hot idle with the motor running 165 fan on but after installing thrasher street chip (engine runs hotter) the oil pressure at idle dropped to 6-7 psi. Seemed to be low from the beginning but as the engine gets hotter the pressure drops even worse.

paul

 

[Steve Wood]

And the rest of the questions I asked?

 

[PaulRV6]

Steve, see above in your first reply. My answers were bolded in with your message (sorry, I guess I don't know how to use the quote very well).

paul

 

[Steve Wood]

Sorry, I did not look at the quote...it's a pain to separate stuff out...

Okay, basically, it looks okay...I doubt new gears would be outside of spec and you got a tight end clearance.

I don't loose clearances but a lot of people run loose bearing clearances and have more oil pressure so I doubt that is the problem.

Did you check the new cover to be sure there was no casting flash in the passages?

 

[Steve Wood]

Also...once warm and the pressure is down at idle...what is the oil pressure when cruising at about 2000 rpm?

Does the pressure respond immediately when you increase speed?

Have you cut the filter open and searched for metal particles inside the filter?

 

[PaulRV6]

Steve, I will check at 2000 rpm cruise and report back. I will also check response with throttle increase. If it is slow response could that be attributed to the 1/8" line going to gage?

paul

 

[Steve Wood]

no...it means that the oil flow is either being lost somewhere or the intake is restricted. Intake to the pump, I mean.

 

[texasturbo]

oil pressure

At my lowest, my oil pressure never got below 20 to 22 psi. That's at 200 degrees or a little more in summer. There are alot things it could be. Main and rod clearance, cam bearings, even turbo and lifter bore. Oil gear, front cover clearance also...

Just my 2 cents worth....

 

[PaulRV6]

DATA FOR REVIEW

Steve, got some data today, it was 85 deg out and engine temp was at 180 deg.
-Cold (first start) oil press at 2000 rpm was 59 psi.
-Idle while warming up was 22 psi.
-After full operating temp (from driving around):
-1750 rpm oil press at 29psi
-Idle hot 5 psi
-Back to 2400 rpm hot oil press is 33 psi

What do you or anyone else think? Problem or not!!! Thanks

paul

 

[randymc1]

I had the same problem after a rebuild. I wondered if it was a problem for a month. Then i checked the oil filter. Massive bearing failure due I believe to excessive bearing clearance. I would cut the oil filter open and check for bearing pieces.

 

[Steve Wood]

It's really hard to say....

I would cut the filter open and look for metal, first.....

I guess if you left out an oil galley plug, it would not have any pressure. Wonder if the oil pressure relief valve under the spring is sealing completely?

You said you had a verified gauge?

Did you check for casting flash in the new front cover?

You sure you had .001 end clearance?

 

[PaulRV6]

I will first check oil filter for metal.

Is there a way to check the pressure relief valve spring?

I had .001" end clearance before I removed cover to fix oil leak. Replaced the gasket but used a very thin film of Hylomar on the surfaces.

Is it possible to have the cooler lines switched so the oil is not being cooled properly?

Do these pressures look alright except for the idle pressure?

paul

 

[Steve Wood]

Whoa...what you had before does not count.

Gaskets are different thicknesses and the sealer adds to it....end clearance could be one problem, then.

Don't think the oil cooler routing would make much difference.

Your oil pressure is a bit low..book says 37# at 2400 rpm.

 

[PaulRV6]

Steve, one other thought. Do you know what the oil pressure switch contacts are set to close/open at? I seem to remember hearing 8 psi and if so, why dosn't my dash lite come on when my gage reads 5 psi at idle? How can I test that circuit.

BTW, I made sure the new gasket was the same thickness as the one replaced with .001". The gasket sealer was only a very thin film on a small section of the surface. Thanks for all responses.

paul

 

[Steve Wood]

I think the switch closes at 4# but I would not take that as a fact unless some verifies it.

A thin film can add up...altho, factory specs have a fairly wide range for end clearance as I recall. I don't really thing that it it....but with a new cover, the pocket may be off a bit.

There are so many things, down stream, that can affect the pressure, it is very hard to tell without going thru everything.

 

[GS70350]

Steve, where did you get the info on the oil pressure at certain RPMS??? like, the 37 at 2400. this worries me now about mine. I feel that my oil pressure is fine, at idle, at 175 degrees or so, with no oil cooler, and synthetic 10w30 and oil stabilizer. it will drop down to about 17 at 650rpm, maybe 15 psi. responds with throttle, really well. responds better with the synthetic than it did with the dino oil. i like synthetic! but, when im driving, crusing at 2400 rpm or so, on a 85 to 95 degree day, when i used dino oil, the pressure would be at about 42 psi or so. then, the longer i drove, the lower it would get, like on the way to BG this year, up hills and all. it dropped down to around 35 to 38 psi or so, which is below the recomended level that you said. what should i do? this is driving it for about 2 hours, with the speed at 75, converter unlocked. using 1 quart every 2 hours. because of the turbo seal. when i put in a fresh quart, it would rise up again for a while, but drop off. thanks for your input.

The starter of this post, i believe your oil pressure is too low, something is wrong, if it continues dropping off, and wont go above 59 at 2K rpm COLD, mine hits about 80 at idle cold, and will hit 90 at 1200 rpm or so. and your idle warm psi is too low for my liking, and lower than the 10psi per 1000 rpm rule. hope you find your problem. check your screens on your pickup, and check your filter to see if its clogged up with crap. might be something simple.

 

[Steve Wood]

The 37# at 2400 comes out of the factory shop manual specs for vin7 engines.