What's your oil pressure???

[Kurt Lesser]

Driving from San Jose to Portland I got to Eureka and noticed that my oil pressure had dropped almost 50% On a normal day it runs 45psi until it warms up and then runs 30psi at speed and 15psi at idle. Now it's running 30psi on startup and 0 at idle. Sometimes the needle is actually slightly below 0. I've also noticed that the pressure will run around 30psi until I let it drop back to idle and then it doesn''t come back up to 30psi. This is why I think the gauge might be faulty. I don't hear anything unusual and suspect that the gauge itself is the culprit. My questions are:

1) Needle position with the run switch on but the engine off?
2) Oil pressure with the engine running coldat road speed?
3) Oil pressure with the engine running warmed up at road speed?
4) Oil pressure with the engine running warmed up at idle?

[Ozhumvee]

Kurt
1/ at rest it sits on the bottom
2/ cold at road speed (2k rpm) 65 psi
3/ warm at road speed 50 psi
4/ warm at idle 20 - 30 psi
My engine has done approx 200,000 kms in 20 years.

I too have a dicky gauge which doesn't read correctly till it has warmed up, been too lazy to change it as yet.
I've also noticed that oil pressure drops in hot weather (30 deg C +) when the engine is working hard/revving.
Oil pressures generally are now higher since installing the 4L80E trans due no doubt to lower engine temps as it is no longer revving its head off on the highway.
From memory there should be a minimum of 10 psi per 1,000 rpm at operating temp.

[dunsbr]

Hi Kurt,

According to the TM Oil pressure with the engine at operating temperature should be:

Stopped: 0psi
Idle (725+/-25): 15-20psi
2,000: 40-50psi

So your "new" numbers do sound a little low.

Sounds like a good time to break out the STE/ICE and see what it says for oil pressure.
That may tell you if it's a gauge/sender problem.

To check the pressure with the STE/ICE:

I. Connect BLUE transducer in place of the oil
pressure sending unit.
Dial test 50 (0-l ,000 psi)(0-5.995 kPa)).
Perform offset test.
2. Dial test 01, interleave with RPM.
Dial test 50.
3. Start engine and observe display
VTM will display RPM first, then PSI

Cheers

[dunsbr]

Hi Kurt,

I did a run for you this afternoon and got the following results on my ~50,000 mile 21year old engine:

1) Needle position with the run switch on but the engine off? 0psi
2) Oil pressure with the engine running cold at road speed? ~55psi
3) Oil pressure with the engine running warmed up at road speed? ~45psi
4) Oil pressure with the engine running warmed up at idle? ~35psi

My engine has a new Oil Press sender and new Oil Press gauge.
They were both fitted to the truckover christmas.

Hope this helps.

Cheers

[kdaniels]

Kurt my 87 m998 with 17k on the engine reads out as follows...

engine off...needle on rest
cold road speed....50-55psi
warm road speed 40-45psi
engine at idle....30psi

i'm running union 76 15-40w oil.


SEMPER FI

keith

[Kurt Lesser]

After installing gauge number 3 my oil pressure now ready almost 60psi at speed cold and 35-40psi running warm. 20psi at idle. The thing that worried me was the 50% drop in pressure after 2 days of driving.

All's well that ends well!

Thanks for your replies.