Rhythmic banging (matches engine speed)

[ulkster]

I live in San Diego (btw, anyone know of a good "Jeep whisperer" who'd be willing to just take a look/listen in person?), and when I drove back from Vegas last week (stopping a few times to give the engine a break) a concerning rattling/banging developed somewhere under the hood. It correlates with engine speed, so it's slower at idle and speeds up as you open the throttle (even in neutral).

With a stethoscope, we noticed that it's louder from cylinder 2 and/or 3 & it accentuated on exhaust runners. There's no smoke, but I think I detected a faint smell in the vent when starting from cold. But it's loud on both sides of the head (driver & passenger), which seems odd?

Our current hypothesis is one of three options (but please correct me if you have better ideas):
1) exhaust manifold leak
2) stuck valve
3) rod knocking (hopefully not)

First video outside:

This is from inside showing how it accelerates as you rev the engine (in neutral):

How do those ideas sound? Any suggestions? And if anyone's especially familiar with TJ's and willing to swing by North Park/University Heights, I'm happy to offer a beer or two to just take a gander IRL.

Thanks for your time

 

[freedom_in_4low]

My calibrated earhole thinks it sounds like half engine speed, which would put it in the valve train rather than the bottom end. And it doesn't really sound like a rod knock to me.

The first video wouldn't load for whatever reason but in the second video, it didn't really sound quite like an exhaust leak either. And if it was, I don't think the stethoscope would isolate it on both sides of the head.

Might be time to pull the valve cover.

 

[ulkster]

Thanks. I tried attaching the first vid again in this reply... does it work after reloading?

Oh whoops, I forgot: 2000 TJ 4.0 manual

 

[Apparition]

@Chris I’ve been noticing that I can’t get any of the uploaded videos on this site to work. Using an iPhone 15 pro max. YouTube’s are fine. Is it just me?

 

[SkylinesSuck]

Works fine for me on a Pixel phone.

OP--I saw your check engine light on and maybe check gauges? What's your oil pressure say? It's hard to tell if internal engine noise or exhaust leak from the vid. You could find out real quick when it's cold. Start it up and move your hand around feeling for hot air blowing out. You'll have 10-15 seconds at least before it gets too hot. And don't lose a finger in the belt

 

[freedom_in_4low]

Works fine for me on a Pixel phone.

OP--I saw your check engine light on and maybe check gauges? What's your oil pressure say? It's hard to tell if internal engine noise or exhaust leak from the vid. You could find out real quick when it's cold. Start it up and move your hand around feeling for hot air blowing out. You'll have 10-15 seconds at least before it gets too hot. And don't lose a finger in the belt

Also pixel but the first video (both times it's been posted) show no preview image and 0:00 for the length and doesn't do anything when I try to play.

 

[Chris]

@Chris I’ve been noticing that I can’t get any of the uploaded videos on this site to work. Using an iPhone 15 pro max. YouTube’s are fine. Is it just me?

It's not just you, I am experiencing it too. I need to look into this so thank you for alerting me of the issue.

 

[ulkster]

OK, I just uploaded my videos to YouTube so you can hopefully see:
First noise video

Second video from inside.

Check engine light scanner result:
P0442
Raw code: 0442
ECU: D1
Status: Confirmed
Evaporative emission (EVAP) system - small leak detected

———————————

Tailpipe moisture - I also took a vid of what seems to be excessive moisture out the tailpipe when I first start her up.

 

[freedom_in_4low]

OK, I just uploaded my videos to YouTube so you can hopefully see:
First noise video

Second video from inside.

Check engine light scanner result:
P0442
Raw code: 0442
ECU: D1
Status: Confirmed
Evaporative emission (EVAP) system - small leak detected

———————————

Tailpipe moisture - I also took a vid of what seems to be excessive moisture out the tailpipe when I first start her up.

Hearing the first video it sounds more mechanical to me than an exhaust leak. Do you have a place and the resources to do your own work or will you be hiring a mechanic? If it was mine I'd be taking the valve cover off to have a look.

It's probably too early to look too deeply into the tailpipe moisture thing. Exhaust contains water vapor after all, and hot exhaust into a cold pipe will condense, and that condensation will accumulate with repeated short runs that don't get hit enough to boil it off (such as the short start cycles done when trying to identify a problem...).

 

[ulkster]

Hearing the first video it sounds more mechanical to me than an exhaust leak. Do you have a place and the resources to do your own work or will you be hiring a mechanic? If it was mine I'd be taking the valve cover off to have a look.

It's probably too early to look too deeply into the tailpipe moisture thing. Exhaust contains water vapor after all, and hot exhaust into a cold pipe will condense, and that condensation will accumulate with repeated short runs that don't get hit enough to boil it off (such as the short start cycles done when trying to identify a problem...).

I have been doing a lot of work on it out at my brother's place since he's got all the tools and more space to work. The only thing is that he's about 100 mi away, I'm worried about driving that far with this noise... is it doing active damage if I drive it? It doesn't feel any different & no odors.

BTW, I'm also hearing from the other Wrangler Forum that it might be a bad piston skirt... does that make sense?

 

[SkylinesSuck]

You should be worried about having to drive it that far and yes, you could be doing more damage. Yes it could be a piston skirt but that's just one of the things that could be causing a mechanical noise if that's what it is. Spun bearing or bent/broken valve train could be others. Nothing good if that noise is coming from inside the motor.

First thing is eliminate the exhaust leak. Do what I said above. If it's not that, change the oil and look for sparkles. If no sparkles, time to pull the valve cover for further investigation.

 

[SkylinesSuck]

And you never answered my question about oil pressure.

 

[ulkster]

(sorry Skylines, oil pressure was fine from what I remember).

It's been a while since I posted, but we were finally able to remove the oil pan (after "exhausting" work taking off enough bolts from exhaust pipe & lowering the skid plate enough for other stuff to wiggle the pan out then raising it back up to reconnect). And yup, definite piston scraps in the oil pan (just like people suggested & I saw in at least another video or two). Check it out:

 

[SkylinesSuck]

Time for a rebuild or a JY motor.

 

[ulkster]

Oh yeah, we had already decided that, this just confirmed it.

 

[Cooper Smith]

(sorry Skylines, oil pressure was fine from what I remember).

It's been a while since I posted, but we were finally able to remove the oil pan (after "exhausting" work taking off enough bolts from exhaust pipe & lowering the skid plate enough for other stuff to wiggle the pan out then raising it back up to reconnect). And yup, definite piston scraps in the oil pan (just like people suggested & I saw in at least another video or two). Check it out:

View attachment 508034

That is very, very unfortunate. That's my worst fear on my Jeep because it's my daily, and there are very, VERY few replacement options for a 2.4.

 

[SkylinesSuck]

there are very, VERY few replacement options for a 2.4.

Untrue. Lots of Magnum v8 and LS motors out there in junk yards!

 

[Cooper Smith]

Untrue. Lots of Magnum v8 and LS motors out there in junk yards!

Too much brainpower for me. If anything it’d be a 4bt or a 4.0 and I'd have someone do it