Sudden Oil Pressure Loss

[mespe]

Ok,

I know this sounds like a blocked oil pickup screen, but maybe there might be something else.

Start a 1983 300SD, after about 20-30 seconds, oil pressure on the gauge drops to ZERO.

Any other suggestions?

Marty

[leathermang]

So it goes to a normal reading THEN drops ?

[aklim]

I had that problem before. Turned out to be a bad sensor. Let me ask you this, do you hear rattling? If not, I would think either gauge or sensor. Probably sensor. Try that first, if not hook up a gauge to the port. Had that problem and panicked and asked Gilly. He said it was probably ok. I was paranoid and brought it to him and he said it was the sensor, most likely since he could hear no rattling which would be present if the pressure was really zero. Changed oil sensor and life was good.

[mespe]

The gauge drops all the way to Zero. I also noticed that it seems the oil in the pan is low when car is immediately shut off, but after sitting awhile, the oil level is back to normal.

Could this oil be going somewhere it's not supposed to be going to? then drain back into the pan?

Yeah I thought sensor too, but when I immediately restart the vehicle, it doesn't take as long for the needle to drop. The needle goes from 3 to 2.8 (for about 1-2 seconds) , then drops as if I shut the car off.

I haven't let it run when it showed no oil pressure, but I do notice alot of oil opn the Cam.

Could it be the oil draining back into the oil pan from the oil filter housing, then it gets pumped to where it's supposed to be, and then I'm really running out of oil???


Marty

[aklim]

When you shut it off and let it sit, the oil drains back from the heads, springs, etc, etc back to the pan, Immediately after shutoff, the internals are soaking with oil from the splashing around and the spraying of the pump. Which is why when I check the oil, I let it sit for a bit. I pump gas and all that before I check the oil level. If it were really getting zero psi, your engine would run bad because the hydraulic lifters would be dry and so would everything and it would rattle and make a lot of noise.

[tangofox007]

Originally Posted by aklim

If it were really getting zero psi, your engine would run bad because the hydraulic lifters would be dry and so would everything and it would rattle and make a lot of noise.

And exactly how many hydraulic lifters does a 617 engine have?

[aklim]

Originally Posted by tangofox007

And exactly how many hydraulic lifters does a 617 engine have?

Whoops, thinking of my gas engines. Anyways, there is oil all over the engine internals and that will lower the oil level till it drips back into the pan.

[tangofox007]

It is quite normal for oil to drain back into the oil pan after the engine is shut down.

To confirm that you have oil pressure, remove the oil filler cap. With the engine running, you should be able to see oil being sprayed onto one or two of the cam lobes. (All of the cam lobes should be so lubricated, but you can only see a couple of them through the oil filler.) That will not happen with an oil pressure of zero.

[aklim]

Originally Posted by tangofox007

It is quite normal for oil to drain back into the oil pan after the engine is shut down.

What he said. If it doesn't, I would be worried.

In fact one of my engines had some special paint put onto the lifter valley to facilitate oil going back into the pan.

Is your engine making a hell of a lot of noise? You'd know if it was. If so, it has a bad oil pump. If it, I'll bet the problem goes away with a sensor or gauge.