Hunting down a knock, bad rocker?

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

I'm getting a loud diesel rattle in the cabin, which isn't really audible outside the cabin. Essentially you put it in R or D and the cabin is overwhelmingly diesel-ly sounding with a rattle, but outside the jeep you really can't hear it. In N or P it isn't noticeable.

At 136 no, at 115 new turbo, new rockers, timing belt, and GDE Eco tune - ran great until about 134k when it suddenly started rattling like this, so I replaced both motor mounts, both of which were bad, along with the crank sensor (crank sensor because it was stalling rarely when hot).

With the new motor mounts the rattle is less, but it is still there.

The jeep idles smoother with the new crank sensor, but the rattle is very audible in the cabin, and not so outside. There are no CELs and it has normal power and pulls as hard as ever, with out any excess of smoke, with a slight trans shudder at speed. Also under hard acceleration the in-cabin noise is almost overwhelming.

I've tightened down the motor mounts, checked the trans mount, checked for rocks/obstructions between the trans / motor and body. We even pulled the intercooler hose to compare the feel and sound of the intake to a jeep crd not making this rattle, and they sound and feel similar. We've looked for exhaust leaks as well.

So we're left wondering if perhaps one of the rockers has failed.

Any suggestions for determining if a one or more rockers has failed, without pulling the valve cover? Any other suggestions for places to look or possible diagnostics to perform before pulling the valve cover?

We have two other Jeep CRDs to compare this one two and this one is unusually noisy in the cabin.

Thanks,

celer

flman · **Posted:** Fri Dec 19, 2014 5:34 pm

Could it be the exhaust hitting the frame?

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

flman wrote:

Could it be the exhaust hitting the frame?

We've looked for that but can't find it any evidence of it.

After digging more on the forums I think I'll do the following diagnostics tonight:

Look again for contact with the frame
Check for loose flywheel/tc bolts
Pull the accessory belt to eliminate the accessories
Check the timing belt/cam/crank alignment

I'm thinking it could be a rocker or perhaps some torque converter issue.

flash7210 · **Posted:** Fri Dec 19, 2014 9:52 pm

It could be an exhaust leak.

I can hear a tick, tick, tick sound sometimes while sitting in the cab or standing away from the vehicle while its idling. But when I stand over the engine and try to listen, I don't hear anything unusual.
Best I can come up with is an exhaust leak somewhere under the vehicle.
Probably from the flex joint.

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

Here is a video of it:

https://www.youtube.com/watch?v=9y0-pShyVpE

Timing the noise it is at about half of the RPM, and isn't really audible outside of the cabin - or perhaps not over all the other jeep noises. The video makes it sound much worse then it does in person.

So I just spent the last few hours pulling the serpentine belt, pulling the starter and checking the flywheel/tc bolts, checking the harmonic balancer, re-tightening the new motor mounts, tracing the exhaust looking for leaks and looking for any contact points between the frame and the engine.

I still have some more investigation to do. It pulls like a monster and doesn't belch black smoke, so I'm leaning towards exhuast leak or perhaps a lean injector.

I do have one new thing to potentially look at, after having the battery unplugged for a while it didn't do it for a few minutes until it warmed up - which is atypical of how it has been behaving, it normally does it at startup. The other odd thing I've noticed is the fuel rail pressure is lower then I'd expect it to be at idle, in the past it would sit at ~6000psi or so at idle, and now it was at 5800psi per my ODBDII scanner; so I'll compare the rail pressure to one of the other CRDs here...

flman · **Posted:** Sat Dec 20, 2014 9:26 am

You did not raise the rpms in neutral for comparison to in gear on your video.

So far I am leaning towards torque convertor, you should try and really hammer it in gear with the brakes on and let it show its true colors.

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

flman wrote:

You did not raise the rpms in neutral for comparison to in gear on your video.

So far I am leaning towards torque convertor, you should try and really hammer it in gear with the brakes on and let it show its true colors.

Is this closer to what your looking for?

https://www.youtube.com/edit?o=U&video_id=QGr2BL2MJHU

That is in neutral to higher rpm and drive to higher rpm, although I think I may have to go higher. On the road hammering it, it sounds like a gigantic air/exhaust leak when you gun it - but I'll be damned if I can find one.

RockyMountainYote · **Joined:** Sun Oct 20, 2013 8:32 pm **Posts:** 77

Celer is my roommate. I have looked at this Jeep and it has even me puzzled. The knock in the video is much louder than in person, and at higher RPM's, the engine has a LOUD growl coming from the passenger side engine area like there is an exhaust leak but there is not any. There was a rock wedged between the t-case and Mopar shield but that did not clear up the problem we're addressing now (but it certainly made us feel 100x better about the transmission since IT TOO was making horrible noises as a result). I double checked the motor mounts and looked for more rocks potentially wedged between the bellhousing and frame but found none. The exhaust does not appear to be rubbing anything either. Power feels pretty good and there's no abnormal smoke. There is an EGR blockoff plate at the EGR valve. I am stumped.

flman · **Posted:** Sun Dec 21, 2014 9:39 am

celer wrote:

flman wrote:

You did not raise the rpms in neutral for comparison to in gear on your video.

So far I am leaning towards torque convertor, you should try and really hammer it in gear with the brakes on and let it show its true colors.

Is this closer to what your looking for?

https://www.youtube.com/edit?o=U&video_id=QGr2BL2MJHU

That is in neutral to higher rpm and drive to higher rpm, although I think I may have to go higher. On the road hammering it, it sounds like a gigantic air/exhaust leak when you gun it - but I'll be damned if I can find one.

Not quite sure of your point, but you are not stepping on the accelerator very hard. I think your jeep sounds normal and you have no problem. Did you want it to sound like your toy helicopter? :SOMBRERO:

Mike92104 · **Posted:** Tue Dec 23, 2014 4:10 am

It sounds like a bad rocker to me. While it's running, feel the CAC hose going to the intake. I'll bet you'll feel pulses that correspond with the knock. The noise is more noticeable on the passenger side because you can hear it better through the air box.

Hopefully I'm wrong,
Good luck
Mike

dthdcrd · **Posted:** Tue Dec 23, 2014 10:34 am

That's almost exactly how mine sounded. I was hunting it for a while until it got so bed it became obvious to find. I found a lot of carbon build up around the #4 injector. The oring, crush washer assembly was leaking. Do you have any exhaust smell in the cab? Check all your injectors. Put a 10mm on each of the bolts that hold the crows foot in place that clamps the injector down. You can also, carefully, push down on the top of each injector while running to see if the sound changes. Before mine got really loud and you could hear the exhaust leaking it started like a knock. I was thinking torque converter hardware and all kinds of things. Good luck it's worth a try.

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

dthdcrd wrote:

That's almost exactly how mine sounded. I was hunting it for a while until it got so bed it became obvious to find. I found a lot of carbon build up around the #4 injector. The oring, crush washer assembly was leaking. Do you have any exhaust smell in the cab? Check all your injectors. Put a 10mm on each of the bolts that hold the crows foot in place that clamps the injector down. You can also, carefully, push down on the top of each injector while running to see if the sound changes. Before mine got really loud and you could hear the exhaust leaking it started like a knock. I was thinking torque converter hardware and all kinds of things. Good luck it's worth a try.

Thanks I looked at this, and some of the injector bolts could have been tightened down, but no evident change and no obvious leak. So I stethoscope-ed around and it's still inconclusive, it's clearly louder on the driver side, and isn't the transmission. What surprised me is how much noise the motor mounts suppressed but yet how loud it is in the cabin. Stethoscoping the frame in random places wasn't helpful either - although perhaps I should try from inside of the jeep to see how the noise is being transmitted as it's really hard to verify there isn't a rock stuck somewhere against the body above the trans or between the motor and firewall.

Did you primarily hear the noise in the cabin? It's been like this for about 1k miles now and is still primarily evident by in cabin noise. The intake is noisy and pulses but no more so then our other liberty CRDs that sound fine.

I'll also try a compression test on it on the off chance one if the cylinders is low, which will prompt me to pull the valve cover and look.

dthdcrd · **Posted:** Wed Dec 24, 2014 7:13 pm

Bummer. I wish it was as easy for you as it was for me. Yes, the noise in the beginning was mainly heard in the cabin. Every time I opened the hood there was so much other noise I couldn't pin point it. Once I got back in the cab it was back. Once it became egregiously loud that's when I could hear it under the hood, but so could everyone I drove by...

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

Well what ever it was reached its end conclusion . All of the sudden on the highway it became too loud to ignore and I have to have the jeep towed home. Still uncertain what it is, but the jeep still had normal power and was making and aweful racket.

If it wasn't christmas eve, and there weren't presents to wrap I'd be diagnosing it right now.

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

Well what ever it was reached its end conclusion . All of the sudden on the highway it became too loud to ignore and I have to have the jeep towed home. Still uncertain what it is, but the jeep still seemed to have normal power and was making and awful racket. To my relatively untrained ear it sounds like a rod knock that went from noticeable to bad all of the sudden - no other symptoms other then a loud metallic knock.

If it wasn't christmas eve, and there weren't presents to wrap I'd be diagnosing it right now.

The really good / bad news is I sold my other car last Thursday, so I have cash on hand to go get another car.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

You should stop driving it if the noise is getting louder. It is sounding more like a rocker issue and potentially a valve slightly contacting the piston. Too much more of that and you risk dropping a valve and wasting the motor.

geordi · **Posted:** Thu Dec 25, 2014 12:43 pm

Guys! Guys! You are hearing hoofbeats and looking for Zebras.

You were on the right track with the engine mounts, but you forgot one. There is a fat rubber mount under the transmission cross member, and my CRD was making similar noises b/c the rubber had failed and the transmission had sagged just enough to be tapping the body. That is why it is louder inside than outside.

Engine noises like rockers are WAY louder outside in the engine bay than they are in the cabin.

For a quick test, see if you can find a decent sized chunk of rubber - in a pinch, Home Depot sells some 2" square 'furniture pads' that you can stack between the mount and the transmission. Jack the transmission right near the crossmember, just a bit, and slide the pads or whatever you found into place, and go for a test drive.

I'd bet money that your noise will be gone.

As an added bit of proof, my TDI was making a HORRIBLE sound recently, and I discovered that the rear engine mount had also sagged and was contacting my skid plate - Every time I was slowing down or stopping... BANGBANGBANGBANGBANGBANG! Did the same thing in a Home Depot parking lot, jammed some of those pads in place and tightened the skid plate against them - noise gone.

Is it a crap solution? Sure. But I haven't had a chance to replace the mounts yet - moving sucks - and this stopped the noise for the time being.

Good luck!

celer · **Joined:** Fri Jan 17, 2014 8:28 pm **Posts:** 12

I think a rod bearing failed in it, it was awful sounding on the side of the road, but not easy to hear with semi's wizzing by, but once I got it home I started it briefly it's clearly screwed up badly, loud rod knock metal on metal sound coming from the engine which is at a the same frequency as RPM. So I suspect a rod bearing failed, if I can find the motivation to go look at it in a bit I will, but I'm pretty sure it's a rod bearing.

WWDiesel · **Posted:** Thu Dec 25, 2014 1:00 pm

Geordi may be on to something??? :ALONE:

When I recently replaced my crank sensor and test drove, it was making a terrible sound when accelerating and I thought what the heck? Drove it back on the ramps and discovered one of the skid plate bolts was in the wrong place the the end of the bolt was contacting the bottom of the motor when the motor torqued up enough to touch it.
Swapped the bolts and put the correct shorter bolt where it belonged and wal laa, NOISE WAS GONE!!!!
Moral of this story; ANY contact by the motor or transmission to any part of the frame or crossmembers will make some very strange and LOUD noises inside the cab but not outside.... :SOMBRERO:

thermorex · **Posted:** Thu Dec 25, 2014 1:39 pm

My trans rubber mount was not shot, but soft enough to make some funny noise when I released the acceleration. This, coupled with a bad axle ujoint made a pretty big noise. I replaced first both ujoints on the rear axle, the noise and the "loose feel" was way less, after trans mount replacement there is no noise at all and it feels like new. You can check the trans mount by grabbing the transfer case from under the jeep and move it up-down and left right. Usually that trans mount sags about 1/4-1/2 inch because the rubber deteriorates in time.

Hunting down a knock, bad rocker?

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