What's wrong with my engine?

My car (2000 Ford Expedition) started making a knocking sound 2 days ago, I thought it was due to the cold weather but when the oil light flashed on I pulled over knowing I was low on oil. When I checked the dip stick I was completely out of oil and put in nearly 5 quarts of Mobil 1 synthetic. Once I put that in the engine started running more smoothly but it still has that knocking noise when I put it under any strain. Does anyone know what I might have done to the engine, and how I can fix it?

By letting the engine run out of oil, you have caused serious damage and you may need to replace the engine or get it overhauled to replace main bearings, rod bearings, piston rings and possibly other parts.

Yep. I know exactly what you've done. You went too long without enough lubrication for the rod bearings. They are now shot, loose, and make a 'knock' noise by banging against the crankshaft during the rotation of the shaft.

This pretty much ends the usable life of that engine. It may get you down the road a little more, but it's destined to die somewhere by throwing a rod through the block.

No

Basically you have killed your engine, through neglect.

The knocking sound is the scored out con rod bearings slapping around. It will soon get worse until something lets go inside the engine.

How do you fix? Buy another engine, either used or a rebuilt "long block'

Hi so here we have a 17 years old Ford which has not had it's oil topped up as a good owner should have been doing. As FORDS burn oil.So when it started with the death rattle you ignored it not being a Good owner.So now it needs a new or overhauled engine.

Let me put this in words that are so simple that even YOU should be able to understand… YOUR CAR IS BROKEN! Take it to a REAL mechanic who can actually look at the car, diagnose the problem and MAYBE even come up with a way to fix what's wrong.

"Does anyone know what I might have done to the engine, and how I can fix it?"

You ran the engine *5* Quarts low. IIRC, the pan holds 6 quarts total. The bearings are no doubt shot now, and there's the real possibility for more damage as well. You can't fix it, the damage is done. Then engine will likely use more oil now than it did before and it's lifespan has probably been severely compromised. You might find yourself replacing the engine or vehicle in the next few months.

Sadly, the 2000 Expedition was notorious for engine problems. This is a job for a good Ford mechanic who can look at the engine and poke around in it. The knock is ominous, and that era engine has had plenty of bottom end and valve train causes of knock, but the real concern is 5 quarts of oil disappearing.

I will paint a less bleak picture than the others: by shutting down immediately I think you have averted the worst of the oil starvation woes. In fact, I would bet the engine can be "de-knocked" for an affordable sum. What I'm less certain of is that there's a bright future for it. The oil disappearance is not going to be a cheap or easy to fix, whatever the cause, and even doing that will not make your 17 year old Expedition a paragon of reliability.

I only see two futures for it: a wrecking yard or a trade-in. If you trade it in the dealer can go through it with "soft labor" (better than having mechanics stand around when things are slow) if they think it is worth it, or they can send it to auction. Either way your own bright future includes replacing the vehicle.

The oil warning light doesn't indicate low oil, it means there's no oil pressure! The engine is repairable but it's a matter of is it worth it?