New knocking sound at idle heard in cab (4.0 SOHC)

[White_4x4Ranger]

So this morning I was sitting in my truck (2003 4.0 4x4) and my school’s parking lot and I heard a slight knocking sound coming from the right side of the cab. When I got out to investigate, I couldn’t hear it from the outside nor could I hear it when I opened the hood. The truck has 196k miles on it with the 4.0 sohc and I recently did oil change with full synthetic high mileage oil. The truck has had one owner before me who was religious about keeping up with maintenance. Previously, I have heard a slight ticking noise at idle and going up to around 3000 RPM that to the best of my knowledge is from the rear timing chain. Any ideas what this could be? I’m hoping it’s not rod knock.

The truck has also had all spark plugs replaced expect those in cylinders 2 and 3 as i could not reach those.

 

[Uncle Gump]

Have you tested oil pressure?

Have you replaced the timing chain tensioner?

 

[White_4x4Ranger]

Have you tested oil pressure?

Have you replaced the timing chain tensioner?

i have not check pressure and it has to the best of my knowledge the original timing set

 

[White_4x4Ranger]

here is a video of the sound
i posted it on youtube as i couldn’t just post the video on here

video on youtube

 

[Uncle Gump]

IMHO... that doesn't sound like timing chain/guide/tensioner issue. That stuff makes more of a rattle.

That sounds more like a knock.

 

[White_4x4Ranger]

IMHO... that doesn't sound like timing chain/guide/tensioner issue. That stuff makes more of a rattle.

That sounds more like a knock.

yeah that’s what i was thinking too, for better or worse. Where should i go from here? Also maybe important to note but i dont hear it on cold starts and it only appears after idling for a couple minutes.

 

[rubydist]

That is the kind of knock you get when the crank damper is loose and rattling on the key. Since you said you cannot hear it from outside, I would guess that it is a timing chain noise. I would start by changing the timing chain damper. You do that by taking off the rf wheel and the fender shield. Bonus: while you are doing that you also change the 2 spark plugs you said you didn't do.

 

[Uncle Gump]

I would test the oil pressure. My SOHC starts cold right about 60 psi. I assume that's where the pressure relief is. Hot idle is 18 to 20 psi. The other thing... oil pumps are positive displacement pumps... the faster they turn the more oik they pump. So at a hot idle... when you increase RPM... Pressure should go up.

I guess you could try and oil additive or using a bit heavier oil.

The lower oil pan will come out relatively easy... and the oil pump can be replaced. I've personally never did one... but people have.

Other then that... treat it like it's an older truck with high mileage. Be gentle on it and from a plan for an overhaul or lower mileage replacement.

 

[White_4x4Ranger]

That is the kind of knock you get when the crank damper is loose and rattling on the key. Since you said you cannot hear it from outside, I would guess that it is a timing chain noise. I would start by changing the timing chain damper. You do that by taking off the rf wheel and the fender shield. Bonus: while you are doing that you also change the 2 spark plugs you said you didn't do.

Are you talking about the timing chain tensioner? I can't find anything on the internet about a timing damper.

 

[rubydist]

Yes, it is a hydraulic tensioner/damper that holds the timing chain from rattling.

 

[oldgeek]

Open the door... Let them in..

Paul McCartney and Wings