A week ago I picked up a 1999 expedition, it ran perfectly fine, small exhaust leak. Yesterday after work I noticed a ticking so I checked when I got home and no oil was even touching the dipstick. So today I put oil in it, and the ticking went away after about 10 minutes. But it developed into a knock and rattling noise. My idler pully is ceased up, could that be part of the issue? This vehicle is solid, good frame and good body, only rust is on the rockers. So I'd love to save this motor, but if I have to motor swap I will. Thank you in advance!

 

Yes. Fix the idler pulley and then see what changes result.

 

I got the idler pully freed up, it's working smooth again but I still have a knocking and slight rattle on the passenger side of the motor. Checked the oil level, it's good and no metal flakes or grit.

 

I got the idler pully freed up, it's working smooth again but I still have a knocking and slight rattle on the passenger side of the motor. Checked the oil level, it's good and no metal flakes or grit.

 

Knocking can be from lack of lubrication, bad fuel, bad plugs or carbon deposits on cylinder walls. Make sure you have good plugs, clean air filter and correct octane fuel. Avoid E15 fuels.

You can try draining about a quart of oil and replacing it with ATF and some seafoam. If it quiets down them run about 50 miles and change the oil and filter again. If it doesn't, you may be looking at major mechanical repair work from a shop.

The rattle could from almost anything.