Knocking/Rattling Top Side of Motor?

[TwoBobsKJ]

Hey All,

Don't know if this sound has been around for a while or not - maybe I just now noticed it. But anyway my OCD nature has me wondering...2003 Renegade 3.7L with 112,000 miles.

When under load - briefly - I hear a knocking that is more of an intense rattling coming from under the throttle body. At first I thought it might be a rod knock but the sound is coming from the topside vs the bottom and it's not a true "knock" that comes from a rod getting ready to let go.

When I say briefly under load, what I mean is if I hit the throttle, as the motor gets up to about 2000-2500 RPM I hear this noise that is loudest on the topside. It doesn't get worse or continue if I maintain RPM's - in fact it goes away. If I drop back to idle and then blip the throttle again I hear it but it stops unless I apply more throttle.

I've listened while under the hood and bumping the throttle with my hand so I'm not in the passenger compartment when I hear it. Like I said, not sure if it's been there for a while and I just noticed or if this is something new...

I'm the 2nd owner - don't have the service records from the PO. It appears the motor has been well taken care of, not stressed excessively but then again I can't be sure.

Thoughts?

Bob

 

[LibertyTC]

I would be tempted to:
1 do compression check. IF IT PASSES-? waterpump? idler pulley-timing chain & sprockets?
2 FAILS Comp check? remove valve covers/inspect.
3 be prepared to rebuild heads.
post a video with sound would help.

 

[Ry' N Jen]

Maybe it's just bad gasoline causing knocking!

 

[TwoBobsKJ]

Thanks guys. Bizarre sound - at least from the standpoint of identifying it with any certainty. Tim, I'm gonna get a video with the sound this weekend and post it - my KJ's innards exposed for all to see and hear :smokin:

Ryan, the sound is "heavier" than knocking during ignition - but not deep enough for a rod knock (I'm pretty sure.) Plus it seems to be loudest under the throttle body. And since the 3.7L is OHC it doesn't appear to be cam-related. But then again it could be one of the infamous 'rotated valve seats.' But those don't knock/rattle under load, do they? And then go away at steady RPM's?

Anyway, I'll have the video and audio this weekend. Gonna take some time away tomorrow to gorge some Thanksgiving turkey... :happy107:

Bob