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Discussion Starter #1 (Edited)
Sedona has 120,000 miles and never any problems. I've taken good care of it, except I never changed the timing belt at 60,000. Recently, I notice a soft thudding sound coming from the front of the engine. It sounded as if it were coming from the timing belt area, and I thought that the belt might be fraying inside since the belt had never been changed. I opened it up this weekend and checked it. No frays, and all the timing marks were correctly lined up. The belt was actually in decent shape for 120,000!! I changed out the belt and water pump and closed it all back up. Started the engine, and there it is again, still intermittent, but definitely there. It's definitely not metal, but I can't figure out what it is. Any thoughts?
 

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2004 Carnival, 2.5L KV6 / GV6 / K5 engine
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99 Posts
How's your hydraulic auto-tensioner. I heard that if these get wear in them the timing belt can start to flail around a bit, which could conceivably cause the sound you are hearing.
 

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'02 Sedona 3.5L
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Kia timing belt is know to break. Regardless, at that mileage, all TB in all car should be replaced (I was late myself :p). From reading your post, I believe your are capable of the job which is not extremely difficult with direction in the forum. I just copy a section of my maintenance record to show you it is not expensive at all for the parts:

At 129.370 k miles 1/14/2012
Replaced:
Timing Belt and 2 utility belts
Water pump
Tensioner and rollers
Spark plugs - 6 x NGK (7090) BKR5EGP G-Power Platinum
Flush brake fluid - Prestone DOT 4 Synthetic
2 x refill steering fluid container
****************************
Total: $450.00

note: If you are replacing the spark plugs when you have the intake off go ahead a replace the rear engine mount, because this is the only way to get to it with the intake removed.
 

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Discussion Starter #4
How's your hydraulic auto-tensioner. I heard that if these get wear in them the timing belt can start to flail around a bit, which could conceivably cause the sound you are hearing.
Hhmm, It sure was a bear to get the pin back in. When I was pushing it in with a vise, I didn't see any oil coming out of it. It seemed fine. Do you know any way of knowing when it is going bad?
 

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2004 Carnival, 2.5L KV6 / GV6 / K5 engine
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Hhmm, It sure was a bear to get the pin back in.
If it was hard to compress then that's a good sign.

When I was pushing it in with a vise, I didn't see any oil coming out of it.
Also a good sign (unless its empty:D but if it was hard to compress then that's not the case).
It seemed fine. Do you know any way of knowing when it is going bad?
Unfortunately the workshop manuals are pretty lightweight on that. The manual for my K5 engine just defines a piston rod extension length (and its not clear to me what failure mode that's even supposed to represent).

The simple test, based on what they are supposed to do, is that they show high resistance when an attempt is made to compress them quickly, exhibit only spring tension when compressed slowly, and spring out rapidly when released.

However a reading of the Gates' website suggests these tensioners have a dynamic response that's carefully calibrated for each engine design, and any wear (implicitly undetectable by any simple test we can do) can alter that. That the tensioner has this non-linear hydraulic setup at all says that these rubber belts must have the potential to resonate & flail.

So in short, I'd say the only way you could know that its going bad is by replacing it unfortunately. Gates say you should change it each time the belt is changed (though cynics would say 'they would say that'). I didn't replace mine when I did the front TB.

I'm not familiar with the 35D engine, can you easily run it with any belt covers off? You could check for any signs of movement. On the K5 engine the RH cover on the front TB can be readily removed & the belt observed while running, steady as a rock on mine when revving the engine, so I figure mine is fine.

As a aside, what I didn't realise until I read the Gates website, is the importance of compressing these things slowly so as not to damage their non-return mechanism, and giving the oil time to flow through the restriction. (I took about 5-6 mins to compress mine). In your case though, there's been no increase in the sound you are hearing after replacement, so that's not a factor. (And of course this assumes its the TB making the noise and we don't even know that that's the case).
 

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2004 Carnival, 2.5L KV6 / GV6 / K5 engine
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Video of failed auto-tensioner

Here's an interesting couple of videos. Not applicable to Didydog's problem as the tensioner here is obviously completely shot. Hard believe the thing's not jumping teeth.

I gather the spring in his tensioner is fine & its the hydraulics that's worn out. Shows these TBs are not like serpentines where a simple undamped spring is enough to keep them in tension.

Hmm, maybe I should have changed mine with the TB as bruce2 suggests above. Watching mine running with the covers off its as solid as a rock, but something to check at intervals.


 
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