Yesterday, I was driving my truck on the freeway, when I lost all oil pressure. I then limped it home at 50 mph, and when I woke up this morning there was a puddle of oil underneath the truck. By the way, it is a 90 2.9 auto 4x4. Any ideas on what this could be? Thanks

 

My guess is you developed a leak and lost enough oil to expose the oil sump. Did you hear any engine noise? How far did you drive during this condition? When oil pressure loss occurs damage begins at that point until the engine is shut down, the significance of that damage is determined by how long the engine runs without proper lubrication. As for the leak, look for telltale wet spots on the engine, or frame, or anywhere you can see fresh oil near the engine. You may have blown a main seal, or even something as simple as the quad-ring gasket on the base of the oil filter. If you can't find the leak from following oil stains, try re-filling the engine with oil and restarting, a substancial leak will show it's self while the engine is running most likely. Also listen for engine noise to see how much damage occured, and please, if it still doesn't produce oil pressure once refilled with oil, don't continue to run it!

 

Well Jake, where fore & aft & side to side, does the puddle of life blood seem to be located????

Could be front or rear main engine seal, or maybe a oil filter base, or canister rolled seam seal, or oil pressure sending unit leak, or maybe a blown out valve cover seal. from loose fastners, or a plugged up PCV valve, causing excessive crankcase pressures.

Give us some more clues & some engine history, any recent repairs, or history of oil leaks????

 

Check for a hole in the oil filter. That was the cheapest valve clatter fix I ever made.

 

Ok, it's never leaked a drop before, I drove it maybe 5-6 miles after it happened. Underneath, it is wet on the front differential, oil pan, driver side suspension and towards the front of the truck. PCV valve is brand new, Valve covers are dry and I have not ran it since so I dont know where it's leaking from.

 

Did you crawl under there and inspect the filter for cracks/holes? It sounds an awful lot like that's the problem.

 

With how far you drove it and from what you say, unless it is obvious like the filter, given the areas you now have that are covered with oil, the only way I believe you can evaluate it on your own is to clean off the oil underneath, fill it with oil and then check for a major leak source. I'd have a buddy ready at the ignition to kill it to avoid further damage if you find a big source. Other than that I'd say you might be in for a tow to the shop. If you really want to be safe, you do the latter first. I guess it just depends on what kind of shape the engine and truck are in otherwise. My two cents.

 

With it wet with oil more toward the front & the oil pan & front differential being wet, I'd guess it's the front main engine seal.

I suppose you could fill it up with oil, start it & let it idle for say half to one minute, shut it down & look to see where it's dripping from.

 

The oil sending unit on the 2.9 is right where you are saying is wet. If you were able to drive it 5-6 miles with what I am guessing was the ( Oil Light ) on and no engine lock-up or noise, Then I would guess the oil sender cracked or broke causeing a oil leak and the sender to trigger the light

Put oil in it and start it - look right under the power steering pump - there is the sender under there that you can get to from underneath the truck!

Hope thats it - cheep & easy fix!

 

A very good tip. I don't know if you 90 has a light or the gauge, which is just a needle version of a light anyway, but you might be able to check the sender for damage first even before you have to add oil and start it. Sure would be great if that was the only problem and you may have skated away without major engine damage. I, too hope that's the problem. Good luck.

 

If the oil filter gasket gets stuck to the motor and then you put on the new filter that has a gasket too it will cause a major leak. Also a stripped out drain plug or lack of a sufficiant washer on the drain plug.

 

I figured it out. Thanks for your help everybody. It turned out to be the oil pressure sending unit. $7.93 and 4 qts of oil and she's back on the streets.

 

That's good to hear! So it actually had oil pressure but was not reading for the same reason it was leaking, interesting! Thankyou for updating us, I learned something today!

 

Credit pawpaw and Rags on this one for honing in on the issue. I think also a real tipoff was [fortunately] the immediate signal of pressure loss but then no major noises or damage indications. If it had been a major loss of oil you'd more likely see that while the fact that it kept on running and otherwise seemed fine makes the sender suspect. Something we all can think about in the future. You may have done this but I guess I'd get to the side of the road fast when the gauge drops or the light goes on, then check the oil level before driving on. If you have plenty of oil at that point, it again would suggest the sender. Glad your truck was saved.

 

Well good to hear it wasn't a crank shaft seal & you have it put right.

Good feedback too!!!!