Oil pressure just went away

So proving the old axiom that no action goes unpunished. Today I took the plunge (for me anyway) of ordering some spiffy new wheels for the Miata. This was followed mere hours later by my 5 mile commute home.

Motoring along quietly, 50 mph, temp just coming up and I notice that the oil pressure gauge is bottomed out. Duck my head and notice the "check gauges" idiot light is conveniently located behind my left hand as it sits on the steering wheel. Well E36 M3.

Pull over into the breakdown lane and pop the hood. Everything looks fine. Check the oil, fine. Nothing visually amiss whatever. Close hood and get back in, fire up the beast to see if it had cured itself (you never know). Nope, still no oil pressure. Sounds ok though and the temperature gauge reads fine. Nurse it on home and everything stays ok (except the darned gauge).

I can't swear it just happened, I've never had an oil pressure gauge give me problems before so I don't usually keep that close an eye on it (except on the track).

So the vital are: 1999 Suburban 350 Vortec 4x4. 235,000 miles. Driven in some pretty heavy snow over the weekend, could the sensor wire be knocked loose? If the oil pump went wouldn't there be other signs? Can anyone point me in the right direction please?

Put another sensor in and cross all your fingers and toes. To me it's more plausible than the oil pump dying but you did say the temp rose first and we all know oil is in charge of 20-30% engine cooling....so...all else I can say is best of luck!

Take a valve cover off and run the engine at idle? If oil gets pumped to the top I would say its the gauge. Hook up a cheap oil pressure gage to any oil passage and check that way? Check the oil pressure sensor and see if its hooked up?

I'm going to say sender. Our K1500 went 280K miles on the factory pump and still built 60psi of oil pressure at all times.

Smart thing to do is hook up a mechanical gauge known to be good and see what it says. If it's not making any noise by now, it's probably not an oil pressure problem.

If you drove it more than 90 seconds and the lifters are quiet, it has oil pressure. Senders, wires, clusters, all fail pretty regularly on GM products built in the last...well, forever, really.

You lost a sender or gauge, hydraulic lifters make very noticeable noises with no oil pressure. 5+ miles of driving with no pressure would have totaled the bearings too, glitter in the oil and knocking.

Sender is at the back of the intake. Likely took a dump. You'd hear the lifters rattling like hell if you truly had no oil pressure.

wvumtnbkr wrote: Take a valve cover off and run the engine at idle? If oil gets pumped to the top I would say its the gauge. Hook up a cheap oil pressure gage to any oil passage and check that way? Check the oil pressure sensor and see if its hooked up?

That motor is a mother to pull a valve cover.

Could be electrical. Check all fuses.

but put another plus 1 in the category of "if you lost oil pressure - you'd know it"

Whatever you do, don't cancel the Miata wheel order. Next thing you know you'll get bitter emails from the owner and have to hash out a multi page thread about it.

I had this happen on the Cherokee recently. Driving along happily, look at gauge. "Oh E36! 2 lbs of pressure!" Pour in 2 cans STP, limp home. Install new sender and now shows 45-50 lbs!

carli had that happen on the 9-7x a couple weeks after we got it. she freaked out, shut it down at her mom's house since it happened there, and called me. sender died.

The Hoff wrote: Whatever you do, don't cancel the Miata wheel order. Next thing you know you'll get bitter emails from the owner and have to hash out a multi page thread about it.

LOL!! I wasn't fully stopped on the side of the road yet when that exact thought had run through my head. Great minds and all

Thanks for all the advice. It's still pretty snowy here so I'll park it for a few days until I can dig into it. Drive the Ranger a bit I suppose.

I had this happen on a CRX once... Turned out to be the previous owners neglect sucked into the pickup... wh00ps..

just out of curiosity ... is it a mechanical gauge or electrical gauge ?

if the former, it should read fine ... assuming the sending unit is ok ... the latter then I would suspect the sending unit to start with

Sounds to me like you're lucky enough to actually have a failed oil pressure sensor for once. If you really had no oil pressure, you would've heard the death rattles and the engine would've ejected piston parts.

Aren't the oil pressure gauge sender and low pressure switch usually redundant systems? Do you have a red idiot light for oil pressure too?

Tyler H wrote: Aren't the oil pressure gauge sender and low pressure switch usually redundant systems? Do you have a red idiot light for oil pressure too?

Not always. Sometimes it's just one sender that feeds the ECU (which drives the gauge) and if it sees the pressure below a threshold, it turns on the light.

Update. Been driving the Ranger all week. Just decided to run the Burban up to the gas station to take advantage of some 59 cent gas (1/2 mile or less away). Engine sounds fine but oil pressure still nil.

Pull away from pump and see the puddle of oil. E36 M3. Baby it back home and take a closer look (jack it up, creeper, etc). BIG active leak coming from the back of the motor on the passenger side. Largely running off the transmission pan.

It's definitely parked until things get better, I'm not pleased about this. Any thoughts oh wise ones?

In reply to KyAllroad:

Rear main or oil pan?

Check oil cooler lines, filter, etc. Anything that takes pressurized oil outside the block.

Bad sender could be leaking too

Failed senders can leak a lot of oil and I think are somewhere on the rear of the engine on a SBC.

I had the center of the sender blow out. 12 miles from home. called AAA