gearhad

97 XJ IL6 4.0 250000miles

Yesterday I started it up, read zero oil pressure, assumed it was the crappy sending unit and drove off, when I arrived I saw I was leaking pretty big from the pan right above where the starter sits. I had my own thoughts, then the thoughts of my dad, and we think there are a lot of possibilities as to what could have happened. So I ask the experts, what could cause a down to zero drop in oil pressure.

Right now I'm thinking, it could be
Oil pump
rear main or front main seal blew and caused loss of pressure
an extreme case of a bad oil pan gasket
can a loss of pressure cause what was once a minor pan gasket leak to become severe?

is there anything I'm missing here that could cause a drop to zero oil pressure? And does anyone know of a test that can confirm or deny any of those problems outright?

Thanks

Dave51

Check the dipsticks of both the transmission and engine to see which one is losing fluid, and how much.

Dave51

With the engine running, of course.

gearhad

definitely engine oil, losing a lot. Enough to be totally not safe to drive, I'm gonna take it to a shop, as I am 6 states away from my shop and tools but it would help to know what is wrong with it so I don't get scammed.

Dave51

And in quarts please.

BlueRidgeMark

Oil pump YES, but a failed oil pump will not cause a leak.
rear main or front main seal blew and caused loss of pressure YES, but the location doesn't sound right. Maybe.
an extreme case of a bad oil pan gasket NO. Oil pan gaskets are not under any pressure. If it fails, it's not suddenly (unless you hit something). But even if a piece falls out, that will cause a leak, sure, but if you add oil you'll get your pressure back (until all your oil leaks out). Did you try that?
can a loss of pressure cause what was once a minor pan gasket leak to become severe? NO. The opposite would happen. If there is no pressure, the leak will be less.


If you haven't tried it yet, buy some El CHeapo oil (doesn't matter what, as long as it's engine oil) and fire it up. See if you can spot the leak, and pay attention to the oil pressure.

One possibility is your oil filter. Either the filter itself, or the o-rings in the right-angle adapter.

EZEARL

Before you start the above you might want to see if the oil pressure sending unit is there.

lawsoncl

Laughing, because I've seen that happen. Have a good look at the oil filter and oil filter adapter. Accidentally doubling up on the oil filter can cause a major leak.

BlueRidgeMark

Oh, yeah, laughing here, too. That is definitely the first step!

boxburn

I just has my oil pressure sender fail on me and was the cause of my loss of oil in that area. My reading dropped to 0 when I lost too much oil.

dave1123

In my opinion, your first mistake was driving off with no oil pressure. Find out why before leaving the driveway.

boxburn

Agreed. Of all things to not work, I'd never be happy to drive with it telling me there's no oil pressure.

BlueRidgeMark

I have tried to drill it into my wife and children, if oil pressure goes to zero, it's an emergency stop at the closest safe location and SHUT OFF THE ENGINE AS SOON AS YOU CAN.

EEVEE

maybe the oil filter is double gasketed?

dave1123

They usually leak on first startup. Not saying it's not so. On vertical filters they sometimes get hit by debris in the road, like sticks or other stuff.