Zero Oil Pressure...No Engine Noise

[unapanther]

I was driving my car yesterday and the oil pressure display came on saying I had 5 psi... then it went to zero. Acceleration caused the pressure to increase into the teens, but no higher. I shut the car down after a mile. I started it up this morning, and the pressure started at 77... within 1 minute, it dropped to zero again. There's no discrenable noise in the engine. The mechanic sounds pretty sure that it's a sensor.

86 Vette, 4+3, 1000 miles on a rebuilt engine (93K original)

If anyone has had a similiar experience, I'd love to hear your imput!

 

[Vettefan87]

I would agree with the mechanic. Have him remove it and hook up an analog gauge and see if there is a noticable difference between the two readings.

 

[speedmaster4]

yep..oil pressure sender...$32 @ napa...right next to the dist,drivers side...those things have the life expectancy of a flash bulb (showing my age)

if u lost oil press for real, rocker arm clatter wuold be very noticeable

 

[Hrtbeat1]

I agree ... Oil Pressure Sender.

Had one go out in my old Dodge PU. Stopped at a light and suddenly the pressure went to zero. Freaked out and shut it down, checked everything, oil level was good, couldn't find anything wrong. Started it up and removed the oil fill cap and looked inside, I could see oil being sprayed inside the valve cover. Drove to the auto parts place and got a new one. That was 100,000 miles ago with no problems so far (knock on wood.)

The one on the Vette is tough to get to. It seems like it is a 1 1/4" but you need a very deep socket, you may be able to get to it with a open end wrench. Good luck.


G

 

[Achilles]

Sorry to hi-jack this thread, but I've got an oil preasure issue very similar. I also have an '86 w/4+3 and my oil preasure after warm up is 17-19 psi at idle. I don't have any engine noise either and my engine runs strong. The thing is, the instrument cluster psi reading is always fluctuating....Cruising = 35-40 psi, Accelerating = 40-48 psi, and of course low psi at idle.

Seems odd. My other vehicles hold a constant reading regardless of RPM, except for my '82, but it doesn't fluctuate to those extremes.

Is this a Corvette thing, or does this sound like a problem w/ the engine or sending unit.

 

[Achilles]

Oops! Just realized that this should be posted in the technical section...

Sorry guys!:W

 

[John Robinson]

I agree

If you had an oil pump malfuntion you would have heard some very expensive noises. Either lifters or con bearings. If your preassure was as low as your gage said the end would come in a matter of seconds. It's would have to be a sensor or the gage itself. Do as suggested put a slave gage in and see what you get.

 

[unapanther]

I have to say that the response time at this site is UNREAL. I feel much better starting the car now and driving it to the mechanic for repairs. All your input is greatly appreicated!

 

[tnovot]

Sorry to hi-jack this thread, but I've got an oil preasure issue very similar. I also have an '86 w/4+3 and my oil preasure after warm up is 17-19 psi at idle. I don't have any engine noise either and my engine runs strong. The thing is, the instrument cluster psi reading is always fluctuating....Cruising = 35-40 psi, Accelerating = 40-48 psi, and of course low psi at idle.
Seems odd. My other vehicles hold a constant reading regardless of RPM, except for my '82, but it doesn't fluctuate to those extremes.
Is this a Corvette thing, or does this sound like a problem w/ the engine or sending unit.

If these oil pressures are consistent and do not change much in the ranges you mention, my guess is that you have excessive bearing clearance and/or a worn oil pump. I believe that a bad sending unit would give much more erratic readings.
I have read that a sbc will idle and run fine at low rpm on as little as 7 psi so you would not (yet) be experiencing engine noise.
Is this a high mileage engine? If so, it might be time for a rebuild.

 

[speedmaster4]

hey chick
mine has always constatly varied oil press readings--3 different engines (none broke) and 4 (maybe 5) senders...as long as variation follows engine rpm,i stopped worrying about it--this is what should happen with a positive displacement gear pump,which the oil pump is..like u tho, never had such "good" gage response on any other car i've owned...did make me uncomfortable at first....probably gage circuit designer didnt want high "damping"...given high lateral accel the car is capable of,fast responding gage is better

 

[Achilles]

This engine has 133,000 mi. on it. The previous owner said it had been rebuilt recently before I bought it....Yea whatever! It has been worked on just by the signs of bolts missing and such. So, could be ready for a rebuild. My oil psi does drop relative to the oil temperature. So it could be worn mains. I guess I'll keep driving it untill performance suffers or I get the money to rebuid, whichever comes first.

Thanks guys!

 

[speedmaster4]

i think the prev owner was honest

nothin at all wrong with the pressures you noted...kinda what i'd expect from an engine with 5k after a rebuild/break-in,especially if it was done right--tolerances .0015-.002 on rods,.002-.003 on mains....these are slightly loose compared original but good for 100k+ --regular oil changes mandatory...better power and gas mileage than original

warm oil will always show less press than cold, even high buck synthetics,particularly noticeable at idle ---some 'racers' that run 'glue' in their engines (50 weight oil) have blown the oil filter off the engine by winging the eng before the oil warms up

 

[Achilles]

i think the prev owner was honest

nothin at all wrong with the pressures you noted...kinda what i'd expect from an engine with 5k after a rebuild/break-in,especially if it was done right--tolerances .0015-.002 on rods,.002-.003 on mains....these are slightly loose compared original but good for 100k+ --regular oil changes mandatory...better power and gas mileage than original

warm oil will always show less press than cold, even high buck synthetics,particularly noticeable at idle ---some 'racers' that run 'glue' in their engines (50 weight oil) have blown the oil filter off the engine by winging the eng before the oil warms up

Thanks for the reply. I hope all is well internally. I tried a synthetic blend once and realized scary low oil psi. Drained it and put conventional back in it. I do make it a point to keep up on oil changes. Sounds like I'm not experiencing anything uncommom. Thanks again!