so i bought a 2000 f150 4x4 4door with 5.4 tonight, i noticed after got it home, at idle sounds like a diesel kinda not really a knock but really faint sound and only standing beside it or under it, in fron of motor with hood up, u dont hear it all, and when rev its gone, kinda like a torqu converter or soemthing at idle only, any sugg?

 

Mine sounds the same way but never have had a problem with it. Mines an 01

 

yea i called the guy i just bought from he said its done that for years, cant even hear it in the hood, only side of it or like in a drive thru, sounds bad, any ideas what it is exactly?

 

Lots of these trucks do it! I talked to the lead mechanic at ford And he said it's nothing to worry about! He said when ford designed these motors they used a bigger piston ring then conventional v8s and at low rpm they are noisy.

I have had 3 of these trucks. A 99,2000 and 2002 all with 5.4 s in them and they all did it a bit. The 2002 had 360,000 km on it when I sold it and did it all it's life!

 

yea i wouldnt think its too serious as higher rpm its gone

 

That's right! My trucks if you raise the rpm just off idle it disappeared.

 

The 5.4 is notorious for having slightly smaller pistons and tight rings, so the low sound you hear is actually a slight piston slap on the side of the skirt. GM did this for years and years. It doesn't seem to have any effect on the engine life, just makes it a bit annoying.

Another noise that is irritating on this engine is the rt side exhaust manifold when it leaks or cracks. Sounds like piston slap also. Again, it doesn't affect anything, just irritates you to death.

Try being a mechanic at a Ford dealership when these engines first came out in 97 model years. Talk about a nightmare to diagnois this sound. There were many man hours, before the TSB's came out, put into finding the problems that customers were complaining of. Wow what a learning experience 96-97 was.

Personally I love working on these motors. The Triton/Modulars are by far, the best engine I've ever worked on. Back in the old days, SB Ford's/Chevy's were the norm and fun to work on. But now, I like what we can do to these motors, and what they can be turned into. Super Snakes anyone???

 

That's exactly what the mechanic at ford told me. I remembered the larger rings but forgot the small piston/ piston slap part. Lol
I guess thats part of gettin old!! Ha ha ha

 

Same symptom here...bought the truck not too long ago. Good to know I'm not replacing anything soon... thought I was forming a knock.

 

if it runs good and has good oil pressure, don't worry about it