Author Topic: Oil pressure drops to zero  (Read 2630 times)

Offline corndiesel

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Oil pressure drops to zero
« on: January 12, 2012, 07:46:22 PM »
I have a question about my trucks oil pressure. Whenever I push the clutch in while driving or if rpm are low enough, say at a stop light, the oil pressure drops off to zero. It only seems to happen after my truck warms up, and it started happening recently. Any help?

Online bd

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Re: Oil pressure drops to zero
« Reply #1 on: January 12, 2012, 08:06:01 PM »
What year model truck and engine are we discussing? 

Check your oil level, feel the texture of the oil with your fingers, and see if it looks clean.  Drop a little oil from the dipstick onto your finger and watch whether the oil quickly tracks along your fingerprint ridges and valleys (grass roots test for fuel in the oil).  Take a quick peek to see if any wiring may be dragging against your clutch linkage and grounding out when you step on the clutch.  If all that seems okay, check your oil pressure with a known good mechanical gauge and we'll go from there.   :)
Rich
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In other words... if people learn by making mistakes, by now I should know just about everything!!
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Offline firefighter

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Re: Oil pressure drops to zero
« Reply #2 on: January 12, 2012, 08:29:13 PM »
It is a mechanical or electric pressure gauge?
Have you done any other motor work lately like changing the oil or thermostat?

How tired the motor is and how thick the oil is can have small factors on oil pressure.
At idle, the oil pressure may drop to 10 PSI or even slightly lower. A gauge that is reading just a little off may show very low oil pressure, but may still actually have adequate oil pressure.

A motor that truly has no oil pressure will start rattling the lifters pretty quickly..... well and other damage too.   :'(

Offline corndiesel

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Re: Oil pressure drops to zero
« Reply #3 on: January 12, 2012, 08:38:05 PM »
The truck is an '84 K30 with a 454. Recently I replaced the intake manifold gasket and I've changed the oil. I used 5w-30. The oil level is steady so I don't think there is any gas getting into the oil and it doesn't smell like gas. And there aren't any funny noises when it idles for a while with the gage at zero. I'll have to check the gage to see if it is broken. I don't know if it is a electric or mechanical pressure gage.

Offline Engineer

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Re: Oil pressure drops to zero
« Reply #4 on: January 12, 2012, 08:59:58 PM »
Validate your oil pressure with a known functioning mechanical gauge. If you still find low op then it is time to look into the engine.

Some causes:
Bad oil filter
Broken oil pump pressure spring
Loose oil pump mounting bolt
Blown/missing oil galley plug
Roached crankshaft bearings
2002 Chevy 2500HD 4x4 8.1/ZF6sp RC/LB
2001 Chevy 2500HD 4x4 6.0/4L85E EC/SB
1997 Chevy Blazer 4x4
1994 Chevy K-2500 4x4 C6P 5.7/4L80E
1979 Chevy K-30 4x4 4sp 4.10
1977 Chevy K-30 4x4 4sp 4.10 454

Dad of an Eagle Scout, and a Life Scout

Offline ehjorten

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Re: Oil pressure drops to zero
« Reply #5 on: January 13, 2012, 03:27:36 PM »
When you changed the oil did you put 7 quarts in?  Maybe a dumb question, but I thought I would ask.
-Erik-
1991 V3500 - Gen V TBI 454, 4L80E, NP205, 14 bolt FF, D60, 8" Lift on 35s
1977 K20 Silverado - 350, THM350, NP203, 14 bolt FF, D44, Stock Lift on 31s
1969 Chevelle Malibu Sport Coupe - EFI350, THM350
1968 Chevrolet Step-side Pickup - 300HP L6

Offline Donut

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Re: Oil pressure drops to zero
« Reply #6 on: January 13, 2012, 06:30:49 PM »
You used 5w-30 oil.  What were you using before? Any additives in the old oil?
Making sure we're comparing apples to apples.
'73 Chevy K-20 ***SOLD***
350/tbh350/np205
My plow was half price if i took the truck with it.

'86 C-30 dually, 454/tbh400

Offline Blazin

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Re: Oil pressure drops to zero
« Reply #7 on: January 13, 2012, 08:38:02 PM »
84 stock should be an electric gauge.
First thing you should get a test gauge, and check it. If it reads good then I would look into checking the sender out, and see if its good, then the gauge.
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

Offline bake74

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Re: Oil pressure drops to zero
« Reply #8 on: January 14, 2012, 07:27:21 AM »
When you changed the oil did you put 7 quarts in?  Maybe a dumb question, but I thought I would ask.

     not a dumb question, you would be surprised how many times people overlook the easy stuff, because it is easy.
#1: The easiest and most obvious solution to any problem is 99% of the time correct.
#2: There is no such thing as impossible, it just takes longer.
  74 k10, 77k10    Tom

Offline thirsty

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Re: Oil pressure drops to zero
« Reply #9 on: January 14, 2012, 07:42:05 AM »
The only dumb question is the one that never gets asked.
Real trucks are built, not bought Build thread

Give me a long enough lever and a place to stand, and I shall move the earth or break this bolt...Whatever, just hold my beer!

Offline firefighter

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Re: Oil pressure drops to zero
« Reply #10 on: January 14, 2012, 08:09:54 AM »
you would be surprised how many times people overlook the easy stuff, because it is easy.

I know you're talking about me and forgetting to check the tank for gas on my snow blower !!!   Ha Ha !!    ;D

Offline jaredts

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Re: Oil pressure drops to zero
« Reply #11 on: January 14, 2012, 07:21:46 PM »
5W30?  Depending on mileage I would think you would want 10w30 or 10w40.  5w30 is a bit light.

Offline Blazin

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Re: Oil pressure drops to zero
« Reply #12 on: January 14, 2012, 08:13:18 PM »
Yeah I run 10w40 in my Chevy's
Some people are like Slinkies. Not really good for anything, but they still bring a smile to your face when you push them down a flight of stairs

 


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