Bad knock at 2000 rpm, this is not an exhaust problem or heat shield etc. Took off the belt and ran the engine, had the same knock. Sounds internal with a whirring sound like a bad berring as well. Crank berring? Cam berring? F250 with 138k just a grocery and kid hauler. Any ideas greatly appreciated, really depressed, possible 4k to replace on one income with 3 kids.

 

How does the knocking sound change with RPMs? Is it consistent but loudest at 2000 RPMs? or does it start knocking at that RPM?

 

Cant hear it on Idle at all, Starts around 2k rpm, It is not a constant knock kinda comes and goes. It is the loudest at that rpm. It will give a short burst of knocking when you accelerate to that rpm.

 

A bad bearing in the engine crank or wrist pin will generally cause a knock regardless of the RPM and change with the RPM so I don't think that's your problem. Is it a knock like a sledgehammer hitting the block or a bunch of ball peen hammers hitting the head? It could be a preignition/pinging problem.

 

Im sure its not pinging/preignition. It sounds like a small hammer hitting the block. Strange thing is it doesnt do it under load just at coast or shift points. I can post a video or send you one, just dont know the procedure

 

Unfortunately video tends to distort sound and it is virtually impossible to tell where exactly is sound is coming from listening to a video clip, it does work well for visual problems.
More questions just to cover everything, does your truck have a auto or manual transmission? And dose the knocking/whirring sound come from the front or the back areas of the motor?

I'm surprised someone else hasn't chimed in with a better answer yet, generally there's a lot more people with more experience than I have answering stuff like this...

 

It is more in the front of the engine. Yesterday I noticed when you shut the truck off it has a hissing gurgle sound on the passenger top side, could be something in the fuel rail/injectors ?? Automatic Trans

 

Hate to tell you this, but I had the same issue with mine and when they pulled the pan it was clearly a bad bearing. At certain rpms (around 2000) it made this noise that sounded like someone beating on metal with a hammer (quickly). It didn't sound like a rod knock as I know it, where you can hear it at any RPM and where it is a consistent, low frequency sound like a bass drum being struck.

If it has just happened your mechanic *may* be able to replace the bad bearing and you can live with it for a while. The PO had already done some (bad) work to mine; I ended up getting a new motor. :-(

The strange part was that otherwise it seemed to run fine -- plenty of power, fuel economy in the 11s.

Anyway, I feel your pain.

 

Is this using the scope or just by ear? The hissing sound could just be the normal A/C pressure bleed down after shutting it off.
Maybe a video could possibly help because I'm having a hard time figuring out exactly what the sound actually is, my small hammer might not be the same size as your small hammer.... My definition of a small hammer sounds like preignition/ping.... and just from stuff I've read on here possibly a spark plug that's loose and working its way to blowing out.... Not sure exactly what your definition is.... A good friend of mine's definition was completely off from mine his small knock sounded like a sledgehammer to me, he thought it was fine just needed some thicker oil... Dumped a bunch of Lucas oil stabilizer in with the anti-freeze that was filling up his crank case and never checked or looked at the oil.... Obviously his 460 truck Engine exploded shortly after that.... I'm not saying that yours will but sounds are defined differently by different people.

 

Update. Hissing sound is being caused by a bad PCV. Two different mechanics have looked at the truck one being a strictly engine rebuilder. Both have said something in the upper end possible a wrist pin. I believe it could be a cracked piston from the way it sounds and acts. I will confirm shortly, I pulled the dipstick and it was a quart low at 100 miles. I was on a slight hill so i will check it later when its leveled out.

For certain not presenting like a lower end sound but if it is that will affect my selling price.

Thanks more to follow

 

Mine had this same thing before I replaced the engine. It was piston slap. The bores were out of round on 6 of 10 cylinders.

 

How's your power at highway speeds?