calee4nyaboy

Hi All, I have an ’02 Z06 with only 8,000 miles on it. It is doing the weirdest thing. If the car is started from cold, the oil pressure gauges reads 45 PSI which is right about where its supposed to be at idle (my ’01 also reads that). The problem is that after about 1 minute (I timed it) the pressure just drops to zero in a matter of probably 4 to 5 seconds…the needle just falls. On its way down, the “low oil pressure” warning comes up on the digital display along with the “ding, ding” noise.

I turned the car off because the oil pressure was at zero. Not knowing if it was a fluke of some sort, I decided to carefully start the car a second time to see if it would go back up to 45 PSI for a minute again and then fall. Well, it didn’t. The needle immediately goes to nothing showing no pressure and the low pressure warning came on again. Keep in mind that the car had only been started for a minute previously and it had been sitting over night so it was cold. In other words, the oil couldn’t have warmed up THAT much in only a minute. And the needle falls fairly quickly, NOT gradually as, for example, if it were falling with rising oil temperature as the car warmed up.

I waited for it to be cold again and tried again with the exact same results:

- Start from cold, oil pressure at 45 PSI (idling).
- One minute later, falls to zero PSI.
- Revving does NOT help bring up pressure even 1 PSI.
- Turned off car.
- Immediately restart the car, zero oil pressure right off the bat.

This can be reproduced over and over it seems. What in the world is this? Right when the needle fell to zero, I carefully revved the engine for a second to see if the needle would jump up and it did not. The oil in the car was changed only a couple 100 miles ago with the Series 2000 Amsoil 0w-30 oil and Amsoil filter. The car has run fine until now and at no time, now or before, do I hear any odd engine noises that might be associated with low oil level. It was changed so recently that the oil is so clear it’s even hard to read on the stick but it is up to capacity so it’s not a low oil level issue. I want to get one of those pressure testing tools that goes where the oil filter goes but I don’t know who sells them. That tool would eliminate a bad oil filter (although highly unlikely) and the sending unit (although I’ve heard when sending units go out, they typically read way to high, rather than low)

I CAN NOT believe this car is doing this. It’s barely broken in. Any suggestions would be welcomed. I am pretty mechanically inclined and could change either the sending unit or the pump if necessary, but lets face it, it’s not both of them so I don’t want to tackle the wrong issue. Heck I don’t even know why either of them would have failed this early on. This really kinda irritates me that an 8,000 mile Z06 left me stranded having to call a wrecker last night.

Thanks guys!
John

1999vettrroo

When my sensor went bad, my pressure maxed out at 80psi. You might want check the connector to the oil sensor. I'm not sure what the sensor would read with an open wire. Start by pulling the drivers side fuelrail cover and reaching your hand back there and wiggling the wire (you'll need another pair of eyes). Hopefully it is something that simple.

rustyguns

my guess....bad sensor

G/L

Oldvetter

There is another current post about low oil pressure, but his does come up when he revs it. He replaced sensor and got same results. Here is his post:

http://forums.corvetteforum.com/show....php?t=1808346

When the sensor fails, it usually fails by reading high. It also reads high with ignition on and engine not running. I doubt if your problem is the sensor.

Have you had this car since new? How long have you had the car? The reason I ask, is could someone had the oil pickup off recently? A twisted or improperly installed o-ring on the oil pickup tube will cause low pressure.

You should hear valve noises when pressure goes to zero, if it really is zero.

You did the right thing as far as not driving it.

Good luck in finding cause. Let us know of outcome.

calee4nyaboy

Yeah, I read that post. He doesn't have the same symptoms I have. My oil circulation system seems to work perfectly, but only for 60 seconds or so. Glad Z06's are fast cuz I apparently I have 60 seconds to get where ever I need to get...LOL

I got this car when it was only a year old. It had 7,xxx miles on it so I have not put many miles on it and it was completely unmolested inside and out so no one has opened her up in anyway. Thats why this is really getting to me.

white90conv

Assuming the sump is full of oil, I would vote for a bad sensor or something wrong in sensor circuit. You need to get a mechanical gage onto the engine.

calee4nyaboy

I would have to disagree. The system works but for only 60 seconds. I have read that when the sending unit goes out it reads way too high which never happens to me. My gut feeling is that I am losing pressure for some odd reason.

Anyone ever used this: Oil Pressure Tool

I'm thinking maybe this would help me diagnose it.

rustyguns

unless you tefloned that engine. when you have no oil pressure it is not going to run very good, your lifters collapse etc. thats why i think its electrical

calee4nyaboy

Absolutely. Since I saw that it just started reading zero PSI, I turned off the engine to prevent damage. How long would I have to idle the engine at zero PSI to hear the lifters collapse making all that noise?

rustyguns

10 seconds

Oldvetter

This is what Chevy dealer's use to diagnose oil pressure problems.

Cobra4B

It may be a failed oil pump... you need to get a mechanical guage on it to verify flow or lack there of.

BlackZ06

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

* Oil pump worn or dirty

* Oil pump-to-engine block bolts loose

* 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

* Broken valve lifters

Repair as neccesary.

=====================================

I would believe it is one of the first five since you are saying you get normal pressure for sixty seconds. In fact, I'd bet on a problem with the pressure relief valve, as it sure sounds like that is opening up and dumping all the pressure from the system.

Check that the oil pressure really is dropping to zero pounds with the test kit you posted above. If it really is dropping, then it sounds like it is time to pull the oil pump.

calee4nyaboy

Okay, the verdict is in: I finally got the KD Tools mechanical oil pressure test kit and attached it to the where oil filter goes. I turned the car on and after 30 seconds or so, the dash started screaming low oil pressure. I looked down at the mechanical gauge and it read 45 PSI. I let the car idle for 5 minutes looking at both the dash and the mechanical gauge and the mechanical gauge never came off 45 PSI but the dash did fluctuate from 0-10 PSI; the needle just kinda floated around aimlessly between 0 and 10 PSI.

I doubt there is a problem with the instrument cluster so it’s something under the hood. So my question is: on the back of the block where the parts are attached for the oil pressure, what all parts am I looking for? Is there an oil pressure switch AND a sender unit or are these two things built in together making it just one part or?

Thanks,
John

BlackZ06

Does the DIC pressure reading agree with the gauge on the dash?

If so, sounds like the PCM is sending bad data.

I'm guessing a wiring issue or bad sensor.

The Oil Pressure sensor has 3 wires going to it from the PCM. A BLACK wire (GROUND TO THE PCM), a GREY wire that is the 5 Volt reference (power supply) from the PCM, and a TAN/WHITE wire that is the signal back to the PCM (varies between 0 and 5 volts).