Bought a 15 model with 80k on it has the 5.0 in it. A week after purchase I noticed a knocking sound coming from I believe the passenger side. Sounds like an old diesel when it's happening. It is not a constant sound. It has only happened twice in 3 weeks.
any help is greatly appreciated.

link to video of noise

 

Oh fudge, that is a big bummer if you don't have an extended warranty. You buy from a private party or a dealer?

 

Rod bearing - crappy deal.

 

 

Bought it through a dealer and is still under warranty. If it is a bearing would it be a continuous sound? After it did it today I turned it off. Cranked it back after work and drove home. And is quite as can be now. Took it to the dealer this afternoon and of course it didn't do it while there. There are no codes and truck hasn't lost any power.

 

If it were me, I would CYA and make sure to take a very good video of it acting up and then capture the overall view of the truck, the mileage and the VIN. Save that video somewhere safe. Not sure how much time is left on your warranty, but you're making a paper trail by going to the dealer, which is good. If after another failed diagnostic attempt at the dealer, go direct with the service manager and see what they can do for you. Show them the video. If nothing with them, keep your cool and reach out to Ford so they can look into it and help you out. Just be respectful, yet firm with whoever you deal with. It'll get you further.

 

Didn't they have issues with oblong cylinders back then?

 

Stethoscope to pinpoint the noise.
How is the oil pressure and don't go by the dash idiot gauge.
A rod knock is generally there all the time.

Piston slap on the other hand can diminish more or less depending on engine temperature.

 

Rod knock is heavily oil pressure / temperature dependant.
Had a #6 rod bearing crap out this summer, the volume and intensity varies each time it was started.

 

Change the oil with a good synthetic (I'd use Mobil1 0/30, or another full synthetic 0/30), and see if it persists. Does it happen only when cold, hot, or random? Cold engines are a lot noisier, but to help with that, that's why I recommended the 0/30 instead of 5/30; it starts lubricating quicker due to 0 being thinner than 5 when cold (and both are 30 when hot). Hopefully it's just old/bad oil. Good luck.