Oil pressure Question... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Longhorn Man · 09-24-2005, 06:07 PM

OK, new one by me...and I have a few ideas rollin around in my head as to why...
At idle, my oil pressure guage (new aftermarket mechanical unit) is fine...reading steady at 20ish.
When i go down the road...or soimply increase RPM's, it quivers...it's too fast to simply say a fluctuation... more of a quiver. It's only a 4 PSI differance...but curiouse as to why.

Longhorn Man · 09-24-2005, 07:19 PM

Hmmmmm, now it is acting fine.

JimKshortstep4x4 · 09-24-2005, 07:23 PM

I am assuming that you have eliminated the gauge as a problem so it is possible that there is some problem in the oiling system. The last engine that I saw with fluxuating oil pressure had lost its oil pump pick up screen. At an idle the oil was getting back to the pan fast enough to keep the pump submerged but at any rpm the oil was not returning fast enough. The result was cavitation of the pump because it was sucking air causing the fluxuation.

Did you try another gauge on it to eliminate that possibility?

Jim

Longhorn Man · 09-24-2005, 07:30 PM

actually just got done doing that...
The pick up was removed and cleaned and inspected about 1000 miles ago, there are no press on parts, and I used thread locker on the bolts...

mjrmn · 09-24-2005, 10:26 PM

It may be air on the oil line running to the gauge. The air is more compressable under pressure than the oil so any slight pulsing from the pump will be amplified at the gauge.
If you used the clear plastic line from the engine to the gauge you should be able to see the air bubbles.
Unfortunately the only way I know to fix it is to crack the line loose at the gauge and start the engine to allow air to escape and fill the line with oil then tighten line.
Do this with the engine cold because it can/will be messy but if oil is cold at least you wont get burned.

powell72 · 09-25-2005, 11:11 PM

I've had times before after oil changes when it is hot out I get air in the line and when I stop gauge goes to zero. Not at every stop, just one time, but I've had it happen after two different oil changes.

Longhorn Man · 09-25-2005, 11:43 PM

I'm still kinda lost on this...it hasn't done it again... just that one day.
I hate problems that fix them selves...they always come back and bite you in the 12 bolt when you can least afford it.

Portmod7 · 09-25-2005, 11:47 PM

Sounds like an oil filter problem to me.

Longhorn Man · 09-26-2005, 12:01 AM

Well, the oil pressure isn't abnormally high, like it was on the bypass valve or anything like that...and it is a 1000 mile old Wix filter...
That could be the issue, but I don't see it as being too likely

*FormerMember* · 09-26-2005, 08:28 AM

My vote is for air, from when you changed the oil pressure guage.

09-24-2005, 06:07 PM	#1
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Oil pressure Question... OK, new one by me...and I have a few ideas rollin around in my head as to why... At idle, my oil pressure guage (new aftermarket mechanical unit) is fine...reading steady at 20ish. When i go down the road...or soimply increase RPM's, it quivers...it's too fast to simply say a fluctuation... more of a quiver. It's only a 4 PSI differance...but curiouse as to why.

09-25-2005, 11:11 PM	#6
powell72 Senior Member Join Date: Jan 2005 Location: Loveland Co. Posts: 3,098	I've had times before after oil changes when it is hot out I get air in the line and when I stop gauge goes to zero. Not at every stop, just one time, but I've had it happen after two different oil changes. __________________ Chris 74 Custom Deluxe SWB 350/350/3.73’s 99 2wd Silverado RCSB 5.3/4L60/3.90’s http://www.classictrucks.com/feature...short_bed.html

09-26-2005, 12:01 AM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Well, the oil pressure isn't abnormally high, like it was on the bypass valve or anything like that...and it is a 1000 mile old Wix filter... That could be the issue, but I don't see it as being too likely Last edited by Longhorn Man; 09-26-2005 at 12:01 AM.

09-24-2005, 07:19 PM	#2
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Hmmmmm, now it is acting fine.

09-24-2005, 07:23 PM	#3
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	I am assuming that you have eliminated the gauge as a problem so it is possible that there is some problem in the oiling system. The last engine that I saw with fluxuating oil pressure had lost its oil pump pick up screen. At an idle the oil was getting back to the pan fast enough to keep the pump submerged but at any rpm the oil was not returning fast enough. The result was cavitation of the pump because it was sucking air causing the fluxuation. Did you try another gauge on it to eliminate that possibility? Jim

09-24-2005, 07:30 PM	#4
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	actually just got done doing that... The pick up was removed and cleaned and inspected about 1000 miles ago, there are no press on parts, and I used thread locker on the bolts...

09-24-2005, 10:26 PM	#5
mjrmn '67 K10 Work In Process Join Date: Feb 2004 Location: Delano MN Posts: 163	It may be air on the oil line running to the gauge. The air is more compressable under pressure than the oil so any slight pulsing from the pump will be amplified at the gauge. If you used the clear plastic line from the engine to the gauge you should be able to see the air bubbles. Unfortunately the only way I know to fix it is to crack the line loose at the gauge and start the engine to allow air to escape and fill the line with oil then tighten line. Do this with the engine cold because it can/will be messy but if oil is cold at least you wont get burned.

09-25-2005, 11:43 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	I'm still kinda lost on this...it hasn't done it again... just that one day. I hate problems that fix them selves...they always come back and bite you in the 12 bolt when you can least afford it.

09-25-2005, 11:47 PM	#8
Portmod7 Registered User Join Date: Dec 2004 Location: Aztec, NM Posts: 388	Sounds like an oil filter problem to me.

09-26-2005, 08:28 AM	#10
FormerMember Account Suspended Join Date: Feb 2004 Posts: 3,051	My vote is for air, from when you changed the oil pressure guage.



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