Hello all. My well-used 2007 F150 4.6l (~235,000 miles) has started making a new and concerning sound. It has had a minor exhaust leak under load for a while (a light "popping" sound under load) as a result of 2 broken exhaust manifold studs at the rear on one side of the engine and 1 broken exhaust manifold stud at the rear on the other side of the engine. However, this this new mystery sound appeared after the truck sat for a few days. The following video was taken from the driver's side of the engine bay. I have not crawled under the truck yet, but it seems to be louder on this side. The frequency of the sound is dependent on the RPM of the engine, and the sound seems to disappear under load. The truck isn't exhibiting any unusual driving characteristics. Can anyone identify this sound?

You Tube

Thanks for any help!

 

Im not that familiar with the 4.6 and its problems but it defiantly sounds like the valve train to me. Does is quieten down at higher RPM? Oil pressure good? Could be a collapsed lash adjuster, similar to a lifter in a pushrod engine or a cam follower. Maybe not getting good oil pressure to the valve train?

maybe someone with a little more knowledge on this engine will chime in but this is a start. Either way I think your going to have to get under the valve covers.

 

how old are plugs? May not be plugs but id recheck torque and rule loose plug out before moving on to worse possibilities.

 

Thanks for the responses.

Yes, it does seem to go away at higher RPM. My truck doesn't have a tachometer, but under "slightly more aggressive than normal" acceleration, the sound seems to abruptly stop at some point.

I forget exactly, but I believe the plugs and coil packs were replaced by me with OEM Ford Motorcraft within the past 10,000 miles. Probably within the last 5,000 (the truck doesn't get driven much by me).

 

Could be a wrist pin.

 

This further leads me to think this is a valve train issue or low oil pressure to the valve train. The oil pressure is normally a lot higher at high RPMs. I know some of the 5.4 motors had issues with the cam followers and lash adjusters, I'm not sure if the 4.6 did.

 

Got a bit of an update.

Took the truck to a nearby mechanic shop that got good reviews. They put the truck on a lift, and their diagnosis, insofar as they could give me one without charging me around $1,000 to disassemble it and investigate further, is that the sound is actually coming from from inside the transmission bellhousing. Their suggested potential causes were the flexplate, torque converter, starter, and/or engine thrust bearing. Now, I didn't think to mention it previously, but I did have the flexplate replaced by another shop within the past 5,000 or so miles, after it failed and left me stranded. I mentioned this to the person I talked to at the mechanic shop, but he didn't offer any additional thoughts or suggestions (he was not the one who actually checked the truck, so he didn't have any hands-on knowledge of the problem). I decided to hold off on paying for the disassembly for the time being.

I did a bit of research, and found that apparently, loose torque converter and/or flexplate bolts can cause a noise at idle. Internet research suggests that there is a port that allows for the easy installation/removal of the torque converter bolts:


Once I get around to picking the truck up, I intend to check them, since it looks pretty easy (no, I don't intend to jump the starter motor like he does in the video. Not safe enough for my tastes). But since I had my flexplate replaced, I am wondering if it may have been done incorrectly (they broke a few of my exhaust manifold studs in the process when they did it). Is there any way to check the flexplate bolts, that doesn't entail unbolting and shifting the transmission back? I don't recall if they are visible/accessible through the bellhousing inspection port.

For that matter, does anyone have any other thoughts on this problem, now that we have this new information? Thanks!

 

flyswat446 Thanks for the response. The parts store won’t be any help. I bought the engine as part of a whole project from another guy that started but wasn’t able to finish the project. (They had 3 kids and his wife got pregnant with twins shortly after he started the project) lol
soo in short I don’t have any sort of warranty. Was part of the risk I took when purchasing.

do you think if I record each lash adjuster as I’m turning by hand and zoom in where I can see that each adjuster is compressing and returning to its proper position would be enough evidence that it’s good? Or would I need to take apart and inspect like you described because of oil flow and possible debri contamination?

 

I just replaced all my plugs, plus coils and injectors. Still kept getting cylinder 8 misfire and multiple and severe shaking at highways speeds at 2000 rpm’s. One spark plug was bad and causing all that mess, even though it was new. Check your plugs, just because they’re new doesn’t mean they work, same with any part honestly. Did you get it figured out though?

 

What I found was a failed lifter on the #4 cylinder on the intake side and a partially failed lifter on the #2 cylinder intake side also. Turned engine until no lobes were fully engaged on the roller followers and took off caps in order on intake side only and carefully removed tested primed and replaced lifters as necessary. put back togather and torqued caps to specs which is 53inch pounds then 45 degrees. Fired her up ticking gone. Issue fixed