Off Topic

[kens96]

I've got a 2001 Suburban 1500 and I have an oil pressure gauge question that one of you might have seen.

Turn the car on and the gauge will go to between 50and 60 PSI. while the engined is running.

Shut the car off and it will drop to 40 PSI and stay there

Turn the ignition to on without starting and the gauge "sweeps" back to Zero.

Come back after 5 minutes and the gauge is at 10 PSI

I disconnected the battery while it sat at 40PSI and nothing happened.

Will always settle at 40 PSI and stay there unless i turn the ignition to run.

While driving the gauge moves normally with RPM between 45 at idle to 65 at 2000RPM highway

Anybody ever experience this? Wondering if it is the gauge or the sending unit?

[Bruce Nunnally]

I am not clear on which Suburban you have, or which engine it has in it.

For the 2001 Suburban with a 4.8L, 5.3L, or 6.0L engine the manual notes under Oil Pressure Diagnosis and Testing

1 With the vehicle on a level surface, run the vehicle for a few minutes, allow adequate drain down time of 2-3 minutes, and measure the oil level.

2 If required, add the recommended grade engine oil and fill the crankcase until the oil level measures full on the oil level indicator.

3 Run the engine briefly, approximately 10-15 seconds, and verify low or no oil pressure on the vehicle gage or light.

4 Listen for a noisy valve train or a knocking noise.

5 Inspect for the following:

* Oil diluted by water or glycol - anti freeze

* Foamy oil

6 Remove the oil filter and install the J 42907 .

7 Install J 21867 or equivalent to the J 42907 .

8 Run the engine and measure the engine oil pressure.

9 Compare the readings to Engine Mechanical Specifications .

10 If the engine oil pressure is below specifications, inspect the engine for one or more of the following:

* Oil pump worn or dirty Refer to Oil Pump Cleaning and Inspection in Engine Unit Repair Manual.

* Oil pump-to-engine block bolts loose Refer to Oil Pump, Pump Screen and Deflector Installation in Engine Unit Repair Manual.

* Oil pump screen loose, plugged, or damaged

* Oil pump screen O-ring seal missing or damaged

* Malfunctioning oil pump pressure regulator valve

* Excessive bearing clearance

* Cracked, porous, or restricted oil galleries

* Oil gallery plugs missing or incorrectly installed Refer to Engine Block Plug Installation in Engine Unit Repair Manual.

* Broken valve lifters Repair as necessary

11 If the oil pressure reading on the J 21867 or equivalent is within specifications, inspect for the following:

* Plugged or incorrect oil filter and/or malfunctioning oil bypass valve

* Malfunctioning oil pressure gage or sensor Repair as necessary

# J 21867 Pressure Gage

# J 42907 Oil Pressure Testing Tool

[kens96]

Thanks Bruce - Its a 5.3 Liter. Don't know if this was the way it was before i changed the oil. Wife's car. don's spend alot of time in it. Only thing that I changed to a FRAM top end filter. Believe its the same one that is on Northstar.

[kens96]

Might have answered my own question. The filter is a FRAM Extended Guard 7000 Mile filter XG3675 with a "Silicone Anti Drainback Valve" I will check in the morning to see if the pressure drops to zero Or I will change the filter to a normal one to see if it makes a difference.

[JimD]

I don't see any problem here if the oil pressure is indicating in the expected range when the engine is running. I'll bet the oil pressure display has operated as you described from day one.

The display is not a "moving coil" meter that will fall to zero. The display is an electronic representation that is supplied by the PCM based on the resistance of the oil pressure sending unit (potentiometer). At rest with power off, the display is arbitrary. The sweep action at KEY-ON is a test.

And there is no way the engine-off oil pressure remains above zero for more than a millisecond or two. The residual oil pressure will bleed off through the bearings practically the instant the pump stops.

[kens96]

Thanks Jim,

You are right about residual pressure I read some more and most filters have the anti backflow in them so it not that.

I will do some more checking. Just comparing it to my 98 vette and it all drops to zero once the car is shut off. i would have expected that the Suburban would doe the same since its other gauges , fuel, battery and and temp do the same.

[Dave in Texas]

Just curious: why would you use a fram oil-filter?

[Ranger]

My thoughts exactly. I'll use a Fram air filter, but NEVER an oil filter.

[kens96]

Thought they were good filters? Get them at Walmart with the Oil (Mobil 1 $25 5quarts). What do you recommend? Prior to going back to my own oil changes (its been awhile) I have ben using Jiffy Lube.

[JimD]

For oil filters I would not use brands other than ACDelco or WIX.

[kens96]

Thanks - for the filter info.

Jim D was was 100% correct about the gauge.

Checked a friends 2001 Silverado and it does exactly the same thing that mine does. Checked another friends 2007 Silverado and the gauge goes to zero but the dash and configuration is different from the 2001. Guess it was a series specific setup. I'll pay more attention next time!

[JimD]

Happy motoring.

Future readers will benefit from your feedback.

[Dave in Texas]

I use Purolator Plus oil filters on both my truck and DeVille. WIX is a very good oil-filter also!

[KHE]

I used to use AC Delco oil filters exclusively but when they stopped making the PF-25 filter that my Fleetwood Brougham takes and replaced it with a PF-414 which is less than half the size, I now use a Purolator filter on that car as its construction is very similar to the AC Delcos and it is still a full sized filter.

I remember the guru stating that the most important filter is the very first filter that is on the engine - 90% of the debris that a filter will catch over the engine's life is caught by the first filter.