I have a 2000 screw 5.4. When I start it up it sounds fine. But after letting it run to operating temp its starts knocking loudly. It sound like its coming from the back of the engine. Speeds up with the rpm and gets a little louder. Id take it to a shop but im in between money. Any clues? I can get a video for sound reference tomorrow.

 

Grab a video and post it to Youtube and then post the link here for us.

 

if you quickly rap the throttle repeatedly, like really fast..
see saw from 2k to say 3.5-4k can you get the noise to get louder & exaggerated?

If so, its most likely a crank rod bearing knock.
Its toast.

Cracked or broken flex plates aren't really common on those.

 

My initial thoughts as well.
A video of it would help with it though.
Regardless, it is not a good thing.

 

Sorry it took so long for a video. But here's a link hopefully it works.

 

So if its a rod bearing would it take awhile to start knocking after it warms up? Starts just fine, quiet and normal. The knock only happens to start after it gets warmed up. Had to drive it today to the backyard and when I give it gas it kind of gets quieter then louder when I let off the gas.

 

take another video...
after its hot & dont be fragile on the throttle....
REALLY rap on it, really high rpm snap of the throttle....
'like 2 tweakers on a see saw...

Youre trying to have it make noise...

You really eased into it....

If its a rod knock, doing what I said will make the rod bearing talk to you....

You cant make matters worse, the damage is done.


Im thicken rod bearings, but the way you snapped the throttle leads to inconclusive.

like get to like 2500 & then qukly snap to 4k, repeat as fast as you can,
Like youre rapping on a throttle on a motorcycle, trying to be the cool kid....

 

Ill get another video up in just a bit if it dont rain.

 

If it is a rod bearing and you rev it too much it could kill the block if a rod comes out the side.