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2008 Optima LX 2.4
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Discussion Starter #1 (Edited)
What do you think this sound is?
Been trying to track down this issue since I got this car a few months ago. Replaced oil, spark plugs, air filter, fuel filter, cleaned MAF and TB. Engine is tuned up.
Replaced belt tensioner and its fixed most of the belt rattle but there's still a bit of noise coming from there.
The engine vibrates a lot when stopped in gear, but is smooth in park. Purchased new front and rear engine mounts, will install soon. There is a 3rd rubber transmission mount and a hydraulic engine mount which are also suspect.
First clip shows when the accessory belt tensioner was rattling and making a racket. Then some clips showing the worn engine mounts. running the engine without the accessory belt. Last clip show the starting off knock from outside the car, accessory belt on.
 

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Please update once you replace those mounts, im looking at doing mine soon. Also details of the process would be good too if you do it yourself. I have the same issue with it running rough idling in gear vs in park.
 

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When does it clunk? When you hit the brakes? When it shifts gears? Just when in gear and sitting still? Which engine? Need more info

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2008 Optima LX 2.4
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Discussion Starter #4 (Edited)
@josmith213 I apologize, it is a 2.4l 2008 Optima. Is my vehicle year/make/model/engine not present under my username to the left? The clunk is present when taking off from a stop. It can be heard in the outside shots in my video.

@ColSwe I replaced the bottom front and rear engine mounts yesterday. It wasn't too bad of a job, used a jack to support the engine. The front mount which is near the radiator only has 4 bolts and comes out easy. The rear mount is on top of the subframe right next to the steering rack. Access is more limited back here. Once the mount was loose from the engine and frame I had to unbolt the motor mount bracket from the engine block to gain clearance.
The idle in drive/reverse is significantly smoother now. It's still not quite as smooth as it could be, though, and something is still clunking slightly when taking off from a stop. Soon I will inspect the transmission isolator, which mounts under the airbox near the driver's side shock tower.
This is what I removed. They were both worn but I think the front mount, which has more cracks in the rubber, was the problem.

 

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2008 Optima LX 2.4
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Discussion Starter #5
Removed airbox and inspected transmission mount. Looks worn but is not torn. Some small cracks in the rubber, similar to the front motor mount. It doesn't seem to be causing any problems besides possibly contributing to a slight vibration in gear.
It appears this transmission mount and the front lower engine mount take the most beating of the drivetrain mounts. If you have a sonata with a rough idle in gear, inspect these components. In this case the most cost effective repair would have been to replace just these two. The original rear lower engine mount was in good shape.
Trans mount pics
 

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I know you said you replaced the tensioner but that belt still looks like it gets loose when you rev the engine. Did you install a new belt as well?
 

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2008 Optima LX 2.4
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Discussion Starter #7
I know you said you replaced the tensioner but that belt still looks like it gets loose when you rev the engine. Did you install a new belt as well?
I didn't. The video of the belt getting loose was before the tensioner replacement. I've considered replacing the belt but it doesn't look very old. Definitely not a bad idea. It still wiggles a bit.
 
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