Rattle / Clatter when idle in drive

[Kieran]

Hi All, my my09 (late 08 built) NT Pajero has developed a strangle rattle when idle in drive e.g. sitting at the lights, it's also notable when easing off the accelerator e.g. when coasting towards a stop. The noise goes away when the revs go above idle or you put it into neutral when at the lights. I've uploaded a video of it to youtube and was wondering if anyone might be able to shed any light on the likely cause/s - https://www.youtube.com/watch?v=tKZReRxLyuk . I'm thinking that it might be the timing chain tensioner or valve clearance is off, but wouldn't the noise get louder when RPM goes over idle? Any insight would be greatly appreciated.

[DGM]

Hi Kieran, I had a strange noise under my car at one stage. I do have a set of the bash plates. It turned out to be the exhaust rattling down onto the plate. Varied from when it was in neutral or idling at traffic lights. Adjusted the exhaust so it had a little bit more clearance and then it stopped the noise. Not sure if this is something you have or your sure that it is in the engine area?

[tonee]

Try have someone in the car put it on drive with the brakes for you and have a listen under the bonnet.

It sounds like something is loose. Bonnet latch, airbox, engine cover etc

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[aussieintas]

Hard to diagnose from the video but look at the simple things first before thinking possible bigger issue. I wouldnt says its timing chain or valve clearence based on the video.

I had a metalic rattle a year or so ago, similar where it would only do it at certain revs and not do it when in neutral. Ended up being a small metal bracket on the exhaust had broken its weld right under the passenger floor area.

As tonee says get a helper to be in the car with brakes on, have a listen under bonnet and under car to narrow down location of rattle. If coming from under the car kick or move the exhaust to see if it stops it or press on the bash plates.

[Seigried]

If you have a provent make sure the lids is on and that the bracket isnt touching anything at low idle speed.

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[Pwoffey]

How many km has the Paj done? Lots of corrugated roads in its history? Once you have checked as many individual items as possible for breaks, looseness etc as others have advised, just check if the engine mounts are not worn out. My NW was behaving very similarly to yours; as soon as I stabilised the exhaust, just by touching it, all the noise ceased, but there was nothing wrong with the exhaust itself or any of its mounting points. Turned out both the rubber engine mounts were worn, almost shredded, and very asymmetrical. The other symptom I had, apart from the clacking, was that when first starting the car in the morning there was a clunk as the engine positioned itself on the damaged mounts. Anyway worth checking if nothing else obvious is loose.

[Kieran]

Thanks all for the suggestions guys. I had my wife sit in the driver seat with the brakes on but couldn't reproduce the rattle. The car has done 180,000 but I've only had it for a bit over a year. It has a provent catch can but no after market bash plates. I might get it up on the ramps over the weekend and see if I can find anything loose.

[Seigried]

Do you still have your bonnet stops? If not your bonnet could be the cause. But not while its up

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[Kingmarz]

I had a nasty knock/rattle in my old Challenger 4m40 at idle and that turned out to be a cracked flex plate Which only cost $70 to replace but took a whole day and a half to install. Some thing happened again about six months later.

[Kieran]

I think I've found the cause or least narrowed it down. Took off the plastic engine shroud / cover and went for a drive and couldn't couldn't reproduce the rattle. It was on reasonably tight with no loose screws so my best guess is it's pressing on something it shouldn't.