This is a follow-up to a thread I posted earlier, about my frightening pressure-drop event of three days ago. 1998 Coupe, 102000 miles, manual.

I was driving normally on a country road and took a fairly hard right-hand turn. Suddenly the low pressure chime sounded and my pressure dropped to about 8 psi. It stayed down around 8 psi for less than 10 seconds and then climbed back up to normal.

Then, one day later, I was sitting nose-down getting ready to pull out of a business parking lot, and the pressure dropped again, while I was sitting still idling. Back down to the sub-8 psi range. I eased out of the parking lot on to level ground and the pressure came back up.

I verified the oil level was good via a dipstick check; I added a quart of oil and a bottle of Seafoam.

Tonight, proceeding downhill at about 45 mph, the pressure started dropping again. It was down to 16 psi when I pushed the clutch in and gave the car some throttle, and the pressure came right back up again.

* * *

o Can the oil pump fail gradually?

o Is the LS1 pump gear-driven or electrical?

o What can I look at, electrically, for something which might contribute? Corroded ground, bad wire, et cetera? Where would I look?

o Can there be scum or crud in the pan, which can partially block the pick-up and then un-block again?

o Can there be an issue with the pick-up?

I'm going to do a complete oil change tomorrow. It looks like I can't drop the pan, without removing a lot of other components... should I let the local independent shop take a shot at this issue?

 

Before I tore into the engine, I would hook up a mechanical pressure gauge and verify that the oil pressure was actually dropping.

Does the valve train make any noise when this low pressure indication shows up? If not it might be a failing oil pressure sensor.

 

Hi There,
My experience with oil pumps( gear shaft usually shears off) is they either work or they do not.You did not say anthing about valve noise.As tn vette stated I would suspect the sensor.A direct reading gauge is a good idea if you have one.Most do not.
robsc501

 

Here's what I would check:
1) listen for valvetrain noise
2) check for any indications of foaming
3) check your pressure with a direct-reading mechanical gage @ the filter
4) when you change your oil, take a close look at the condition of the oil coming out and also cut open your old filter and inspect it

In the absence of any abnormalities related to items 1 & 2, I would suspect (like TN Vette and robsc501) that your problem is related to the sensor/sending unit.

What temp does your oil usually run at?

FYI - GM's specifications for (hot) oil pressure are:
6 PSI @ 1000 rpm
18 PSI @ 2000 rpm
24 PSI @ 4000 rpm

Also, the fact that your low pressure events occur when the car is pointed nose-down is interesting...

 

As to valve noise... I did not have any, that I had previously noticed - until yesterday. Now I have a rapid ticking noise - tickticktickticktick - from the driver's side of the engine compartment. But - the ticking is only present, after the car has been driven for a while and the oil temperature is in its usual 201 - 203 degrees F range - and it's only really audible when the car is parked, idling, in my garage (echo chamber).

I didn't hear any valvetrain noise when the pressure warnings occured and the car is behaving normally, for its standard value of "normal".

 

I would definitely put a direct reading mechanical guage on the car. The OEM sensor with it's tendency to fail is notorious. It doesn't fail just high. There are many reports of it failing low. And it does not always fail hard one time. You mentioned adding Seafoam to the oil. Have you changed the oil and filter since that time? I would.

What is the oil pressure at idle when you hear this ticking? I would be suspecious with the ticking that there is an internal problem. If you have a mechanics stethoscope try to identify if it is just one cylinder or more than one. Also check both sides. I had what I believed to have been a octane related ping under load on a GM engine and suffice it to say it turned out to be much more than an octane ping. Try to get a handle on this sooner than later if you are even thinking of keeping the engine.

 

I changed the oil and filter today.

Getting a direct-read pressure gauge and placing it where I can see it, while driving around, will be somewhat challenging.

 

You don't and shouldn't drive it with the mechanical gauge connected.

This is to compare the readings of the dash gauge / DIC display for oil pressure to the hot / cold engine oil readings on the mechanical gauge.

 

What is the concern here?

 

Sorry, was thinking about a temporary test gauge with poly line. There isn't a concern if it is a screw in type or one that can be temporarily or permanently mounted.

 

I checked DTC codes today and I have the P0522 historical. Now... low oil pressure sensor voltage, isn't the same thing as a code for low oil pressure, correct?

As I said, I did the sensor relocate back in May; it's the kit from the local friendly Forum vendor.

Lot of oil pressure threads lately...

 

It might be. No way to tell with out further diagnosis. When oil pressure is high the resistance in the sensor is high and the corresponding voltage is high. When the oil pressure is low then the resistance is low and the corresponding voltage is low. The PCM posts P0522 if the voltage is low ( less than 0.48 volts) for more than 9 seconds.

Sooooo, if your oil pressure really is low then the P0522 can get posted.

Of course if you have a relocated sensor then you likely also have some type of extension harness for the sensor. Problems with the harness or connectors could cause the code to be posted as could problems with the sensor itself.

As I said above, a lot more diagnosis is necessary to know what the P0522 is caused by.