kshields2

I have been having a problem for a couple of weeks on my 2004 f150 fx4 5.4. the problem is at high rpms it starts to make a rattle noise. I was told it might be the cats, so I replaced all of them and it still does it. I checked the heat shields they feel tight. oh and if you rev it parked or in neutral it dosent rattle. nothing ticks on the truck. And it sounds like its coming from underneath the cab but I could be wrong.

Nalb1221

What kind of a rattle noise, metal on metal, chain rattle? And you'll need to pinpoint more exact where it's coming from. Tons of things on theses trucks can make noises so you'll have to be more exact.

kshields2

Its hard to pinpoint where exactly its coming from because its only when the truck is moving. What it sounds like is a heat shield rattling kind of like marbles in a can and it sounds like its coming right underneath the cab. It only does it for a couple seconds when the truck is under load and then it goes away until the truck revs up again like getting on the freeway or when you step on it or pulling a trailer

GrimaceTimus

Pre-detonation? Exhaust manifold leak?

Nalb1221

Do you have any rattle at cold startup? It could be the timing chains they tend to rattle for a quick second when there's an oil presure problem. Does the truck have a ticking or diesel sound at hot idle?

kshields2

At start up little tick but idle there Is nothing

kshields2

And there is no loss of power at all

GrimaceTimus

Sounds to me like an exhaust leak. That being said...

My father-in-law works for a state agency in maintenance. He and his crew do most of the maintenance to their fleet trucks (all F150s and F250s with 5.4 3V) but when they have a major issue they go to the DOT mechanic shop.

I had been recently sharing my timing component / phaser noise issues with my father-in-law. He had some conversations with the DOT wrenches that work on these things every day. If in fact the noise you are hearing is a timing chain, these guys seem to thing it is the tensioner or tensioner arm (failing). According to them, they see the most tensioner failures on trucks that do a log of towing and spend a lot of time in the higher power-bands.

I guess that could correlate to a tensioner with a very small leak that is only a factor at high RPMs and thus high oil pressure (65+ PSI).

But again...based on what you describe, I'd be leaning towards exhaust leak (or the broken manifold stud thing).

kshields2

I do tow a small snowmobile trailer up north with a couple quads and a couple dirt bikes on it but it is nothing for the truck and it does not stuggle. Other than that it is a daily driver and is not put under any huge load. A mechanic at a muffler shop took it for a ride and said it sounded like an exhaust leak but couldnt pin point it. It also makes the noise when like I have cruise on and I go up a slight incline at low rpms, where the cruise just gives it slightly more throttle but does not loosen up the torque converter or drop a gear. If it is an exhaust leak it would have to be at the headers because the whole exhaust system was replaced from the headers back with a borla set up and it did it before and after the kit was installed.

deliverance

Vacuum leak in the 4 wheel drive? Under load it'll try to engage the front hubs and it sounds like your dragging chain link fence