Have a 2003 Ford Expedition 5.4L Automatic 4WD EB. I have a strange clang/rattle that initially I thought was possibly a rod or bottom end bearing or even an bad exhaust mount.
However, it wasn't constant in that some days it never shows up for a day or four and the next thing you know it happens and its all day long, and mostly noticed it at all load levels and rpms. Verified it wasn't the engine as i put her in Neutral and took it to like 45000 RPM and no engine knock. Clang...anything. Climbed underneath and it sounds like it is coming from the transmission/center area underneath. With it in park you can rev the truck and you'll hear the clang mainly as it spins down. When I do hear it, it is when the engine is coming down off a reving session. Almost sounds like a loose exhaust pipe or something since it sounds like you're clanging on hollow steel.
Is it possible that one or more of the bolts that connect the engine to the flex plate/TQ could have come loose? or does this sound more like a broken flex plate? I've never heard what a busted flex plate sounds like as even in my Lightning ive never broke one. I have video of it however ill need to convert it so its compatible with the sites upload file extension compatibility
Any help would be greatly appreciated.


Mike

 

I had a similar issue with my 03 a couple years ago. It ended up being the element in the driver's side secondary catalytic converter. Manually downshifting to engine brake rattled it worst. I had my wife rev it in Park while I crawled underneath with a hose to pin point the rattle.

No required emissions check in FL, so I cutoff the secondary cats from both sides to balance and haven't had any issues. The O2 sensors are before and after the 1st cat, so no codes.

 

@broncoholic This is what i was also thinking/fearing....a screwed up cat. Sadly here in Texas we have inspection so cutting out a cat is not really an option for me. Unless somehow by some sort of shear dumb luck cutting em out does not throw a code thinking the idiot light to come on. And im not gonna drop the cash on the thing to have it tuned as thatd be pointless in my eyes.....and thats if I can find someone to cut the cats out and weld in pipe.


Now you mentioned you crawled under yours with a pipe to pin point the rattle? I assume you place one end of the pipe against the cat and your ear in the other end kinda like a stethoscope?



Mike

 

I have an old water hose from a washing machine, but a scrap piece of garden hose is good too. Yes, use it like a stethoscope. Hold one end to your ear and moving the other end to find the noise. I initially had the same fear as you, rod bearing,, something in the tranny or cracked flex plate.

No check engine light with removing the secondary cat. The computer doesn't take any measurements after that one. If you have emissions inspections, they may fail you for cutting it out and replacing with a straight pipe, even if the engine light isn't on. A local exhaust shop should be able to tell you how strict your state is.

 

@broncoholic I may have some hose around and will try it out and see whats up.
Sadly out here im well aware of how hard these guys take emissions testing. My Lightning has no cats at all, no egr etc etc....it never passes unless I pay for a "special" inspection if you catch my drift. So if my cat is toast its gonna super hard to do anything but replace the thing with a new one as my old exhaust guy who would cut cats retired years ago And I have yet to find anyone that's willing to do the work again.
Thank you kindly, and ill update once I figure out what the heck is going on

 

And that clanging turned out to be..... the drivers side upstream cat was all busted up and broken inside. Replaced it with a new unit and life is good.

 

You're lucky it didn't clog and cause other issues as well.