rattling noise under light throttle... with video

[EL SHO]

Hows it going guys?

Well Im here with a new puzzle trying to resolve. Its a rattling sound that is mostly heard under really light throttle when in gear. It is also heard but bearly when in park or neutral but at higher RPMs.
This sound is no present when the car is cold only after it has been driven for a few miles/mins and is noticeable only from the inside of the car and not from the outside (probably cause of other ambient noises).

Got any ideas what could it be?

Recent work done to the car is: new spark wires, NGK spark plugs, new coil pack, valve cover gaskets, new Tstat, fresh 10w-30 oil and new coolant.

Heres the video I was able to record. You may have to raise up the volume and/or use headphones. Hope you can see it.

http://youtu.be/xr5k6ZwDCBw

 

[jimtash]

I can't tell what it is because of the video quality. Cats going bad will rattle at low RPMs.

Can you tell the area where it's coming from.

 

[EL SHO]

I can't tell what it is because of the video quality. Cats going bad will rattle at low RPMs.

Can you tell the area where it's coming from.

Yeah I know it's not the best audio quality, I tried to make a better video but seems I can't get the audio to be clear enough.

Well the car doesn't have any cats, looks like they were removed long ago. It's got a catless Y-pipe. Unless there are any other pre-cats that I'm not aware of and havent seen them ¿?

I believe the sound is comming from close to the firewall. Once it has warmed up it will start doing it.
To try to best describe it.. it sounds like.. mhhh 'marbles' going around or when you have really worn out spark plugs and going under load.

I was thinking of valvetrain noise but once I get under the hood it is not possible to hear and I think valvetrain noise will be heard at all times and not just when the engine is warm/hot. I've gapped the spark plugs correctly and always use 93 octane to prevent pinging/detonation.

I'll keep on trying to make a video with better sound quality.

 

[jimtash]

It might be the camshaft chain tensioner. Over time they can wear out causing the chain to rattle against the guard because of the loose tension and it makes itself apparent at idle or light load. My experience has been to hear this happen only when the engine is warm and it sounds like marbles rattling under the valve cover but is only intermittent. Pay attention at the rear where the chains are located. Put your hand around that area and if you feel any vibration at the same time you hear that noise, it's the chain banging around.

 

[EL SHO]

It might be the camshaft chain tensioner. Over time they can wear out causing the chain to rattle against the guard because of the loose tension and it makes itself apparent at idle or light load. My experience has been to hear this happen only when the engine is warm and it sounds like marbles rattling under the valve cover but is only intermittent. Pay attention at the rear where the chains are located. Put your hand around that area and if you feel any vibration at the same time you hear that noise, it's the chain banging around.

ohh ok.. I got the idea now. Alright, I will try that!

I remember that when I replaced the valve cover gaskets I looked at the tensioner for the front side (looked good and the chain had/has tension), but not at the one at the back close to the firewall.

You know how hard are those to find replacements in case that's the issue?

 

[jimtash]

Put a wtb ad on here if you need one. If it does turn out to be the tensioner and the plastic pad is still good, you might be able to fix it by taking it apart and cleaning it. Sometimes they become clogged.

Make sure of you do buy a tensioner, it's for the rear head. They are not interchangeable.

 

[Mike Spataro]

engine rattle

I had a similar issue some years ago on my ATX SHO and the noise was heard in the rear of the engine and was hard to find the source. After lots of time investigating the problem, turned out to be the timing belt tensioner was bad.

I suggest you take the top cover off of the timing belt and see if the belt is jumping. Strange as it seems at idle it makes noise (like a rattle) but if you give it gas it gets quiet.

Good luck.

 

[EL SHO]

Put a wtb ad on here if you need one. If it does turn out to be the tensioner and the plastic pad is still good, you might be able to fix it by taking it apart and cleaning it. Sometimes they become clogged.

Make sure of you do buy a tensioner, it's for the rear head. They are not interchangeable.

Ok I'll keep that in mind then, thanks! BTW... are there any difference in the tensioners between the 3.0 and 3.2 heads?

I had a similar issue some years ago on my ATX SHO and the noise was heard in the rear of the engine and was hard to find the source. After lots of time investigating the problem, turned out to be the timing belt tensioner was bad.

I suggest you take the top cover off of the timing belt and see if the belt is jumping. Strange as it seems at idle it makes noise (like a rattle) but if you give it gas it gets quiet.

Good luck.

Thanks Mike.

I actually checked that not long ago, this rattling sound was already present, I was checking to see if there was anything loose and if the timing belt had good tension when my harmonic balancer went out so I took the top and middle covers off, ran the engine that way and no sound could be heard from there and everything looked ok, I could even see all the way to the bottom even if I didn't take off the lower cover.

 

[jimtash]

Nope, no differences between the ATX or the MTX. From now on just remember the only differences between the two besides displacement are in the timing belt set up and also the serpentine belt set up. Also the alternator will be different. Other than that, they are both mechanically the same.