Knocking/tapping noise coming from driver side exhaust manifold

[Crmsntide27]

2000 F350 with about 250k miles on it. There is a knocking tapping noise coming from the driver side exhaust manifold. No codes have been thrown. There was some black soot below the driver side exhaust manifold so we changed the up pipe gaskets on both sides but that didnt fix it. Put aftermarket exhaust manifold gaskets, ran the engine without the belt, and checked hot side of turbo for cracks. Everything checked out and the sound is still there. We are thinking warped exhaust ports on the head or maybe a damaged valve. I dont know if the owner does his own maintanence but the sticker on his window says he hasnt changed his oil in about 25000 miles.

[Crmsntide27]

Any suggestions?

[HOUTX01X]

maybe it is still leaking through up pipe gasket?? couldve gotten to the point of no return. i went with bellowed up's so i was sure not to have any probs...in any case... for ya for a real mechanic to chim in

[melmount]

cyliner 8 cackle. if it sounds like a lifter but loud thats it. Its what what mine are doing. I dont know whether you have an ad injector in that hole or an ae. The ae was fords fix for this but it helped did not always cure it(long lead injector). A regulated return for the fuel helps due to the dead end fuel system. Rear up on cylinder 8 cackle. do a google search. lots of info on it.

[nine6stroker]

I'm no 7.3 expert, but I've heard it can either be noise from cylinder 8 as melmount said, or a stuck/bad injector can cause a pretty damn loud knocking.

[melmount]

bad injectors can do it but if you run a buzz and a cct test when the motor is cold in the morning it will tell you about the injectors.(it will have to run a bit to get the oil warm enough for the scanner to allow u to run the test but it will still be cold.(engine temp wise) When there cold is when the injector will most likely show a defect.

[nine6stroker]

Good call, completely slipped my mind to mention a buzz test...

[melmount]

the rocker arms should be retorqued too, if never done. I think its 20 foot pounds

[Crmsntide27]

Originally Posted by melmount

cyliner 8 cackle. if it sounds like a lifter but loud thats it. Its what what mine are doing. I dont know whether you have an ad injector in that hole or an ae. The ae was fords fix for this but it helped did not always cure it(long lead injector). A regulated return for the fuel helps due to the dead end fuel system. Rear up on cylinder 8 cackle. do a google search. lots of info on it.

We checked the injectors and I guess the cylinder 8 injector was replaced because it's not a long lead injector, all 8 injectors are the same. I don't know if that has something to do with it or not.

[Navy Diver 5342]

I have the same issuer but Ford says there is nothing wrong and I am getting 20.2 mpg. I say go back to school because I'm only getting 14 mpg or less. I have been told to check all exhaust and under the y pipes from the turbo. That's my next check. For any mechanics that work for Ford on this site you all are full of crap. You just use a computer to check things out. Get a real job and investigate!