'00 AWD 5.0 Sporadic sound at high rpm after Seafoam

[oddball101]

Hey there, I recently purchased a 2000 5.0 AWD Mountaineer (167k miles). I had some buyers remorse but after hearing the motor, it wasn't hard to fall in love with that V8 sound, even though it had some misfire issues.

So here is what's up. I put a half can of Seafoam through the PCV and the other half in the gas tank. I took it out for a spirited 15 min "wake-up drive" and then let it idle in my driveway for another 10 min, occasionally revving, bumping it between 5-6k to work the Seafoam through it's systems and then let it idle again for a few. The last time I revved it up, I was sitting in the seat (door open, hood down) and heard a random "scratch/clank" at around 4-5k.

It sounded like it was coming from under the Mounty as I could hear it better the closer my ear was to the floorboard. I popped the hood and instantly realized the sound was actually coming from the top as it was much more prominent. My first thought was a fowled lifter because I've heard rod knock that eventually turned into a 3.0 rebuild, and the sounds were very different.

This sound resembled more of a steady "tick" matching the rpm's. The next morning I got another can of Seafoam and put it in the crank case, drove it around softly (for the most part) until I heard that "scratch/clank" sound again with the scratch coming just before the clank. I mean to me, it sounded like a dryer would occasionally tossing a lighter or a coin from your pant pockets.

Work caught up to me over the past week so I went to go through the motions again last night and after about 20 minutes of revving and letting it idle in park, it started making that sharp scratch sound again like it did before just before it started ticking but this time the ticking didn't occur, just the occasional sharp scratch at higher revs. I was standing over the motor to better listen and the puzzling thing is that the scratch sound is hard to place as in it could be deeper in the motor and not where I originally thought I heard the ticking up top.

I figured as much detail as I could would help, so I hope this wasn't too long winded..

I am at a loss because otherwise the motor sounds great. Anyone have any ideas here?

 

[Cranmaro99]

Post a video when it makes the noise and post it for us? Doesn't sound good to me, however.

 

[oddball101]

Yes, I will do that. It is kind of hard though because I don't know when it'll make the sound but I will try and catch it.. I'll just babysit her until she does I guess.

 

[radman]

I would say reving a 167K engine at 5-6K rpm in neutral is a good way to pick up an engine in a bucket. You might look for a bent push rod, fulcrum, stud, or broken rocker arm.
Mike

 

[SoNic67]

Is your oil pressure gauge steady? Or tends to fluctuate with warmed engine and idle rpm's?

 

[oddball101]

SoNic- Yes, the oil gauge is steady without flickering but I will go over it again today since I'll be home early from work (sinus infection, bleh).

radman- Understood.. I was thinking if I pushed it a little that the motor would "tell" me if something is wrong after the Seafoam and it did. I suppose I am lucky in the sense that I haven't gone through the swap yet and I will be able to get some work done on it when I get to pulling the motor.


The previous owner did say that he recently replaced the tranny and that is the same spot I thought I originally heard that sounds. I am beginning to think that the two sounds may not be from the same cause.

The lifter did start to tap up top (or so I think) shortly after I heard that sound but that was also after the Seafoam and I've heard that it can cause the gunk to choke the lifter until it pushes through. I haven't heard the lifter tapping sound since.

The past two times I've been out there running out the rest of the gas in the tank (1/16th tank), I have only heard that random scratch sound so I think the Seafoam did its job on the lifters.