Engine rattle when in drive

kj75 · **Posted:** Thu Dec 17, 2015 4:43 am

Hi all,

I have a 2006 Jeep Cherokee KJ Diesel with 127000 kilometers.
I have been trying to diagnose this strange rattle sound without luck. Seems to only occur when in drive and reverse while idling. At normal speeds all is OK. I replaced both engine mounts recently so I can rule that out. I took a video with the aircon off and moving between drive and neutral. Jeep drives fine and no smoke at all. Surely if it was an engine problem it would manifest itself regardless the auto was in drive or neutral.

Could it be a pulley making the noise ?

Any feedback would be welcome.

https://www.youtube.com/watch?v=mT6funWfjLE

WWDiesel · **Posted:** Thu Dec 17, 2015 7:56 am

Remove serpentine belt and start engine, place in drive and / or reverse and see if noise is gone. If noise is gone, check alternator override pulley for any dust/rust signs behind cap on front of pulley and check belt tensioner pulley for wear or bad bearing, or weak tension spring; any one of these items can cause belt idler pulley to bounce at idle and make noise.... :wink:

kj75 · **Posted:** Thu Dec 17, 2015 3:23 pm

The alternator is brand new (2months old) so another thing I can rule out.
However it does sound like a pulley, so I will remove the serpentine belt and see if I can find the fault.

SargeIndustries · **Posted:** Thu Dec 17, 2015 3:31 pm

Check your torque converter bolts. You will have to remove the starter and rubber access plug. They backed out twice on mine. It sounds like a loud diesel knock when the bolts are hitting the aluminum transmission to engine adapter plate.

kj75 · **Posted:** Thu Dec 17, 2015 7:55 pm

Would there be a guide on how to check the torque converter bolts with pictures ?
If I get a shop to do this, how much time should I expect them to charge ?

geordi · **Posted:** Fri Dec 18, 2015 2:58 am

Guys... Hearing hoofbeats and thinking zebras? He's from Aussieland, you should be thinking of much more exotic creatures! :mrgreen:

I'd check the transmission mount first rather than the converter bolts - it is MUCH easier to get to, and will take all of about 10 minutes to do a test. Use a jack and lift the transmission tail housing just a bit behind the support crossmember - leave yourself some access, because you will want to shove a thick pad of rubber into the space that is created in the center of the mount. Home Depot (a hardware store in the states) sells these furniture pads, that are 2.5" squares of rubber about .5" thick. Shove one of those or something similar into the gap between the top and bottom of the mount, and test drive.

If the sound is gone... You can replace the mount for $150, or just leave that rubber pad in there and call it done.

kj75 · **Posted:** Fri Dec 18, 2015 6:29 am

Thanks Geordi, that is a great idea about the tranny mount. I have a big 1700km drive from Brisbane to Cairns and will try your idea as soon as I can. Have a fantastic Christmas. :JEEPIN:

rankom · **Posted:** Fri Dec 18, 2015 6:47 am

also if you remove intake hose and idle engine , check for pop pop back pressure noise just to check rockers?

thermorex · **Posted:** Fri Dec 18, 2015 7:46 pm

I one don't think it's the transmission mount. It sounds as you have a bolt loose somewhere in the engine compartment or a pulley. If you pull your e brake and accelerate lightly, does it go away? I want to see if you only have it when the engine is on load. Did you try removing the serpentine belt? Also, you may try with a mechanical sthetoscope to try isolating the noise. If it would be from the transmission, you can crawl underneath while is in gear and listen. I would first just try isolating the noise. The transmission mount has bolts up and down, and unless the bushing is broken, I'm not sure how can you stick anything under it, unless Geordi means to stretch the bushing and add some rubber around it. But just lifting the transmission about 2cm while in gear, you should see a difference in sound. Could be also motor mounts. Could be many things but most important is to try and see where the noise is coming from.

rankom · **Posted:** Fri Dec 18, 2015 10:32 pm

I think this sound like unbalance fuel knock , when in drive engine is under some load so ecm requesting more fuel , i personally like spending money on injector testing.

Sir Sam · **Posted:** Sat Dec 19, 2015 1:06 am

Check your Harmonic balancer. Mine failed at it rattled pretty good at idle but would quiet down under load and when it got warmer.

Mountainman · **Posted:** Sat Dec 19, 2015 2:30 am

Is it a metallic clacking sound? Sounds a lot like the one I just put together the other day, and it turned out to be a leaky fuel head. I primed the bulb rapidly while it was idling and the sound went away completely... I'd be curious if that does anything to yours?
I was imagining metal on metal from the sound, but it was just air.

The balancer bolts being loose can also cause some fun sounds, especially when it flies off. Blue locktite please :JEEPIN:

Oh, I also wouldn't be surprised if there's a collapsed rocker or two. Have you ever gone into limp mode on a major grade? If you pull the cac hose off of the FCV, does it have a hollow popping sound?

kj75 · **Posted:** Sat Dec 19, 2015 3:46 am

The sound is like metalic marbles or metalic clacking and seems to only occur mainly when in drive or reverse idling. Once the Auto is put in to Neutral the sound is gone. I think the problem is more evident when car is fully warmed up. The sound seems to go away once I apply gas and accelerate. The car drives OK, and no smoke at all. Fuel consumption is around 8L to 9L / 100km (depending on fuel).

I initially thought the problem was the front engine mounts so had replaced them, but this didn't solve my problem. I never changed the auto mount.
I have also replaced the fuel head recently as the old one leaked diesel through the connection.
Previously I was told by the dealer that the injectors were tested OK, but not sure I can beleive them.

I took a reading of the MAF via ODB diagnostic and it shows 17.2 g/s while idling here in Brisbane when engine is fully warmed up. I used the Torque Pro software on my Android phone and a Bluetooth adapter.

The car only went into limp mode once the CAC hose unplugged (my fault for not putting it on tighter).

The car seems to drive fine apart from this strange noise.

Sir Sam · **Posted:** Sat Dec 19, 2015 12:09 pm

kj75 wrote:

The sound is like metalic marbles or metalic clacking and seems to only occur mainly when in drive or reverse idling. Once the Auto is put in to Neutral the sound is gone. I think the problem is more evident when car is fully warmed up. The sound seems to go away once I apply gas and accelerate. The car drives OK, and no smoke at all. Fuel consumption is around 8L to 9L / 100km (depending on fuel).

Aside from more evident when warmed up this sounds like what happened when my harmonic balancer went bad. I'd still recommend you check it.

Pull the belt off, start it, and then listen to the noise. If you still hear it with the belt off it could still be the balancer.

Next pull the balancer off and shake it. It may make an obvious rattle. Then if you start without the balancer on if there is no noise its likely the balancer.

rankom · **Posted:** Sat Dec 19, 2015 12:45 pm

if you say ,rockers are ok go to next level … common rail diesel crd,cd,cdi rattle , injector problems,,,,,,,,,,

Mountainman · **Posted:** Sat Dec 19, 2015 12:56 pm

If it's not the balancer, you may be sucking air at the tank. Your sound description sounds just like what I was experiencing.

I read that some diesels have more of a metallic clack than others (of the exact same make and mileage), and it had something to do with harmonics of the bottom end, but they said it was a normal diesel engine phenomenon. I still think you have something strange going on though.

I can't find the MAF readings specs...but I think 17.2 is low for 92 ft elevation isn't it? I think I had 17.8 or 18.2 at 2000 ft when I checked. From what I've seen, most rockers are wasted if EGR has been active for 80k miles or more, sometimes more, sometimes less

kj75 · **Posted:** Sat Dec 19, 2015 3:14 pm

Unfortunately EGR has been active on the Jeep for 125K kilometres before I disabled it via an ECU remap. I bought the car used 3 months ago and it was not making this noise initially. I recall my wife came home and told me she was parked on elevation. She put the Jeep in reverse but started rolling forward so she applied too much acceleration and she spun the tire. I think this noise came soon after.

According to the service history the car has been serviced every year. Motor oil changed at 10k kilometers intervals and auto transmission fluid changed at 50K km and 100K km. Timing belt kit and thermostat was done when I bought the Jeep at 125K km. The Jeep seems to have been well looked after and I would find it strange to have serious engine or injector problems especially with relatively low kilometers.

Mountainman · **Posted:** Sat Dec 19, 2015 3:41 pm

kj75 wrote:

Unfortunately EGR has been active on the Jeep for 125K kilometres before I disabled it via an ECU remap. I bought the car used 3 months ago and it was not making this noise initially. I recall my wife came home and told me she was parked on elevation. She put the Jeep in reverse but started rolling forward so she applied too much acceleration and she spun the tire. I think this noise came soon after.

According to the service history the car has been serviced every year. Motor oil changed at 10k kilometers intervals and auto transmission fluid changed at 50K km and 100K km. Timing belt kit and thermostat was done when I bought the Jeep at 125K km. The Jeep seems to have been well looked after and I would find it strange to have serious engine or injector problems especially with relatively low kilometers.

hmm, I've seen rockers collapse at 88k miles, and recently someone reported the same at 60 some miles. If she got the rpms way up there maybe a rocker went south. I've had them break under high load and rpms. Someone will probably chime in with what the MAF should be. That will probably tell you if it's the rockers, as long as the air filter is clean, or removed.
Higher EGT's might also be an indicator. I blew a head gasket violently on one that had some broken rockers. Less airflow = quick failure with aluminum heads.

Hopefully it's not the rockers, but many of us that want our CRD's to last pull the top, put in new rockers if they're not like new, and add ARP head studs, because the head gaskets almost always leak eventually. Just like a VW diesel or subaru outback...

rankom · **Posted:** Sat Dec 19, 2015 3:44 pm

ok kj75 i know your jeep is low kms and looks very nice, and maintenance is good ,but this is not an old bullet proof diesel say like land cruiser toyota or similar , this is nice unique crd diesel not design to last like the old diesel , don't worry just do what all of us did , rockers , injectors health test , that all you need or if not happy you can spend more money and be happier , just smile and life is good .

thermorex · **Posted:** Sat Dec 19, 2015 6:42 pm

17g/s is close to factory 18-ish at sea level. Rockers are fine. Move to the next step. Isolate the sound, see where is coming from. Then think what can go wrong on that area. Get a mechanical sthetoscope and stop wasting time checking a bunch of things randomly.

Engine rattle when in drive

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