Never heard this sound before

talon660

Registered User
I have a steady knock-knock-knock noise at idle, about two beats per sec. It doesn't sound like piston/bearing knock and goes away after throttle. It sounds exactly like two 1" dia. ball bearings being struck together. I removed the sc belt to see if the shaft spring had went bad, still the same. It is coming from somewhere in front of the engine. Possibly exhaust leak? How do I check? Motor mounts make this noise? It doesn't sound like normal valve/lifter noise to me. It has been getting a little louder ever since the rebuild.

111K, 11K on rebuilt motor.
 
Could be water pump going bad or exhaust leak, or any other number of things. Take some throttle body cleaner and clean your throttle body, then, have someone start the car while you look for any type of black smoke coming up from along side of the engine. If you see black smoke come up from the side of the engine then it is a leak. That is how I found mine.

You can check your motor mounts by either visual inspection or by opening the hood all the way, set the emergancy brake and then start the car, put the car in gear and give it a little bit of gas (do this in Drive, or 1st, and also do this in reverse) While your doing this you want to look through the front winsheild with the hood open and you should be able to see if the engine displays any type of abnormal movement ie, jumps more than 1/2 inch or so when you hit the gas while it's in gear.

Could also be valve tap, or rod knock, it is hard to say without hearing it.
 
Get a stethescope and listen to all of the moving parts on the front of the engine like the other 2 belt tensioners because they will click like that sometimes. Also try to listen for your timing chain although rare, it could be making the noise. Good luck
 
I had a lifter that the check ball had a piece of fiber stuck in it and it would tick at idle or when there was very little load on the engine like shifting between 1-2 (automatic) while cruising. Stethoscopes are cheap, I recommend you get one as they work 10 times better than the screwdriver to the ear trick.

Jeff
 
Thanks for the tips guys, would brake clean create black smoke able to see? I need to get a stethoscope. Hey 1BADSC, what does your AMG run in the 1/4? Will it smoke the WS6?
 
Do not use anything other than Throttle Body cleaner on the throttle body. It has a specail coating that can be stripped off if you spray other stuff on it. Never had the AMG to the track but it doesn't even come close to the Ws6. The AMG is only around 230HP at the engine compared to a bone stock LS1 at 305-310 at the rear wheels.
 
any news?

Any news on the situation?

I beleive that I have the same problem. My friend is a master diesel truck machanic and tends to think the my timing chain is the cause of the clanking noise.

I hope that it is the timing chain and nothing inside the engine because I just got this damn car running again and can not afford to not have it running.
 
I have pretty much narrowed it down to the t/r tensioner pulley using a stethoscope, with a little out of the alternator. I replaced that tensioner a while back with the rebuild, but it usually wobbles back and forth, don't know why, maybe another pulley is out of round? If if was an engine knock it would have broke something by now by the way I drive it. Also a Master Ford tech told me maybe I could have exhaust binding or a leak at the headers. He also said timing but it seems fine when I drive it, just idles low. I still need to do a air compressor check for a suspected vac leak somewhere behind the blower.
 
doe the sound go away if you remove the drive belts? My noise did not, so that is why ithink mine is coming from the timing chain.
 
The car will run without the belts. Don't run it long, the engine will overheat but it is a great trouble shooting tool

Aaron
 
I don't know about overheating but if you run without the SC belt then wire the bypass open.

If you don't every time you mash the pedal the valve will shut and cause the air to push it's way past the rotors. Each rotor weighs 4 pounds and that is a lot of weight to turn. Causes a lag.

Jeff
 
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