Unidentified Intermittent Noise at Idle

xhizzous · **Posted:** Tue Oct 28, 2014 11:12 am

I am getting a tapping or rattle at idle.. more than normal. It disappears under any load .. even slight load if I increase throttle at all. I can really only dicern it inside with the windows up. It also only seems to happen when the engine is warmed up.

I am worried about it being something having to do with the lifters and having to tear down the top end but maybe its not that. It is my daily driver and has performed superb so far. I hope my luck has not run out.

Timing belt was done at 115k with the help of jeepdan. Im sitting at 134k mi right now. Have been running with ORM for the entire time I have owned it. Since about 94k miles.

Any suggestions are very welcome.

WWDiesel · **Posted:** Tue Oct 28, 2014 11:39 am

I had a rattle noise at idle when hot that was louder when the AC was on. Turned out to be the serpentine tensioner pulley was weak. Replaced it with a new one from ID Parts and noise disappeared.

New one had much stronger tension than old one... :!:

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

I had a metallic rattle only at idle. I could swear to you the torque converter was coming apart, but it was actually the motor mounts. Never heard metallic noises from a bad motor mount until CRD.

xhizzous · **Posted:** Tue Oct 28, 2014 12:16 pm

Thanks for the replies. Im going to look into the tensioner and Motor mounts hopefully this weekend then. Nothing has been running any differently .. but unidentified noises coming from the CRD are kind of scary.

Do you know of any good way to tell if the motor mounts are bad for sure?

SargeIndustries · **Posted:** Tue Oct 28, 2014 3:23 pm

Check your torque converter bolts. They backed out twice on mine and only made noise at idle.

ebbnflow · **Posted:** Tue Oct 28, 2014 5:04 pm

Could also be alternator decoupler going bad.

WWDiesel · **Posted:** Tue Oct 28, 2014 9:21 pm

ebbnflow wrote:

Could also be alternator decoupler going bad.

It thats the case, look for tale-tale signs of red dust (rust) on the inside recess of the alternator decoupler pulley..... :idea:

papaindigo · **Posted:** Wed Oct 29, 2014 9:35 am

or noticeable, not slight, bouncing of the serpentine belt tensioner at idle

xhizzous · **Posted:** Mon Nov 03, 2014 8:15 am

Tore the starter off Friday so I could get to the rubber plug / TC bolts it was really messy down there. I tightened all of the bolts there... none of them seemed to be rattling loose.. but they were not tight either. I also dont see the telltale orange rust powder on the Alternator decoupler.

I did find 3/4 of a 5/16 wrench sitting on top of the starter... someone had cut the open end off to shorten the overall wrench. I know it is not mine, so it has probably been there since before I purchased the jeep at 94k miles... now Im sitting at ~135K so it has been sitting there for 40k miles. Im surprised it stuck around that long.

Im still looking for the noise making culprit.

Unidentified Intermittent Noise at Idle

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