Please Help Me Identify This Knocking Noise!

[sixOHfour]

This is my 2000 GT, 36,250 miles on it and it has been making this metallic knocking sound for a while now, id say the last 6 months. It only starts once the engine is fully warmed up... when the car is cold it does not make this sound.

I had it compression tested and its all good 185+ psi on all 8, no weird misfire, runs good, no oil consumption etc. You can only really hear the noise at idle.. it seems to go away after 1200rpm.

You can hear the noise the best on the second half of the video once i move the camera into the front wheel well. Anybody heard this noise or know what it is?


View: http://www.youtube.com/watch?v=G2IY5Bi2h9Q

 

[Mattstang04]

What kind of exhaust do you have? Do you have an offroad midpipe? It could be valve train noise through the exhaust pipes. I can sometimes hear valve noise resonating through my pipes.

 

[TheDeuce193254]

Have you checked to see if the EGR is stuck open a little, it could cause a lean misfire type condition at idle but would go away at cruising speeds

 

[trinity_gt]

Get a mechanic's stethoscope and check around the front cover. It could be timing components; tensioner arms or chain guides.

Any metallic glinting in the oil? If the chain guides have worn enough and you have aluminum arms the chains can start cutting into the arms, machining away bit of aluminum.

 

[sixOHfour]

Thanks for the input. I changed the oil today and there was quite a bit of metal at the bottom of the drain pan... I dont have a stethoscope, but I ordered one cause I couldnt find one locally. Thing is, is when you stick your head under the hood you dont really hear it.. just the injectors. My problem is obviously bad though with the discovery of the metal in the oil. I cut the filter open and there was no metal in the filter.. not a single speck. Weird.

My EGR is working OK, and I only have catback flowmaster's. with the stock catted mid pipe.

Anyways, Its bothering me quite a bit. Now with the discovery of metal in the oil I'm pretty worried. The car is parked for the winter now, but I seem to be losing sleep. I might rip the valve covers off to see if i can feel any timing chain slack from there without pulling the cover off for now. Ive heard quite a few loose timing chains, but this is unique if thats what it is. Ive also never heard a bearing, rod, pin, or even lifter sound like this before.

 

[KENS89LX]

Notorious 4.6 issue...cam phasers..

 

[trinity_gt]

Notorious 4.6 issue...cam phasers..

It's a 2V; no phasers on these mills.

 

[sixOHfour]

Still waiting on the stethoscope to come.. its coming from overseas so it will take a while.. lol. Ive posted this elsewhere and nobody seems to even have an idea. I hope its something simple like the tensioners.. Having to buy a new one or rebuild my engine would suck badly. Especially since its got such low miles and its been religiously maintained..

 

[1987stangman]

LOL.... Phasers on a 2v..


Anyway, if you do get curious and decided to pull the valve covers you can see pretty well down into the timing chain cover using a flashlight, just enough to make sure there is no offending chain guides or tensioners. The cars mileage would suggest that they should be fine but i had a 96 gt that I had put a 04' motor in with 65k on it and got a broken guide on the drivers side of the engine about 5k miles later, in contrast my current Mustang is also a 2000 and now has 109k on it and the guides and tensioners are still good. If one is broken It could explain what your finding in the oil as I have seen the chains rub the bolts that hold the guides onto he block. Do you have a picture of the oil with this metal in it?

 

[sixOHfour]

I wish I did have a pic of the drain pan.. I stupidly looked at it, swore at the car and proceeded to change the oil on my winter beater.