Massive Engine Knock on All Startups

[racingmason]

So I spent the day replacing both header gaskets with new stock ones. Surprisingly easy when you dont have to pull the headers out. The noise is still there. On initial start you car hear the noise almost on top of the valve train on cylinder number 8. As the engine warms up the noise goes away until you hold constant throttle around 900 to 1800 rpm it has that sound like rocks in a dryer. You cant hear it on top much if hardly at all and it's more prevelant on the passenger side and from under the car. A stethoscope hasn't helped much as it seems the same all over when its idling. The only thing I havent checked is the blower bearings. I did see on the corral a guy had a noise similar to this and it was the number 5 rod bearing. Hopefully the oil sample is done soon.

Any ideas on other things to test would be great. Might just pick up a harbor freight borescope and check all 8 cylinders tomorrow. The car is going into a mustang shop to turn cylinders off next week for further diagnosis.

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[Sig556]

So I spent the day replacing both header gaskets with new stock ones. Surprisingly easy when you dont have to pull the headers out. The noise is still there. On initial start you car hear the noise almost on top of the valve train on cylinder number 8. As the engine warms up the noise goes away until you hold constant throttle around 900 to 1800 rpm it has that sound like rocks in a dryer. You cant hear it on top much if hardly at all and it's more prevelant on the passenger side and from under the car. A stethoscope hasn't helped much as it seems the same all over when its idling. The only thing I havent checked is the blower bearings. I did see on the corral a guy had a noise similar to this and it was the number 5 rod bearing. Hopefully the oil sample is done soon.

Any ideas on other things to test would be great. Might just pick up a harbor freight borescope and check all 8 cylinders tomorrow. The car is going into a mustang shop to turn cylinders off next week for further diagnosis.

Man you have been through the ringer. Best of luck hope you solve the mystery.

 

[choate]

Obviously nobody can diagnose a car from their couch but that sounds exactly like my buddies 03 cobra when he hurt his motor. 3 pistons were scored. Not saying you have 3 scored pistons but the KB blowers are known for producing a LOT of heat. To me. Sounds like a bent rod and now your piston is shot. Personally I def wouldn’t even drive it like it is but that’s me

 

[96gt4.6]

I think your diagnostic path is pretty sound Mason, least to most intrusive is the path I follow as a professional. As you stated, my next step would be a cylinder bore inspection, followed by cylinder cancellation to determine which hole/holes will quiet the noise down once they are cancelled out. If you eyeball something with the boroscope that you can clearly see is damage, at that point you could go ahead and proceed with teardown and skip the cylinder cancel in my opinion.

Hearing those videos, it still just screams internal engine, perhaps piston crown/ring land damage, possibly rod bearing as stated. There is clearly some metal scraping/extremely abnormal sound there, in my opinion. Like choate said, hard to diag from a keyboard, but after 14 years of doing it professionally, my money is still on internal engine damage, but really I do hope I am wrong!

 

[racingmason]

I think your diagnostic path is pretty sound Mason, least to most intrusive is the path I follow as a professional. As you stated, my next step would be a cylinder bore inspection, followed by cylinder cancellation to determine which hole/holes will quiet the noise down once they are cancelled out. If you eyeball something with the boroscope that you can clearly see is damage, at that point you could go ahead and proceed with teardown and skip the cylinder cancel in my opinion.

Hearing those videos, it still just screams internal engine, perhaps piston crown/ring land damage, possibly rod bearing as stated. There is clearly some metal scraping/extremely abnormal sound there, in my opinion. Like choate said, hard to diag from a keyboard, but after 14 years of doing it professionally, my money is still on internal engine damage, but really I do hope I am wrong!

Its nothing to diagnose anything. I was thrown to left field because it goes away once it gets warm and it came out of nowhere after some easy driving for mounts. The last time it was ran hard was in October before the weather cooled off. Could it have been when a plug fouled out last spring and it's just now showing up? I wont really know until I get it tore down. I dont run it past 7k or beat it off the rev limiter.

I appreaciate the help and reassurance that I was ot losing my mind. I assume some cross hatching on the cylinder walls is normal from the machining process but vertical grooves would signs of wear.

The blower is fine. I spun it with a single phase ac motor slowly from 100 up to 8k rpm through gears on my work bench. It's pretty damn quiet except for the massive whine from no intake. It's crazy how much air it moves. When think about 2.9 litres it doesnt sound that big but spinning it at 8k it moves air and it gets HOT.

 

[Blown86GT]

As some have alluded on this thread, its time to pull the motor out and perform diagnostic tear down. Its interesting to read advice on this thread and realize only half the folks on this board actually know what they are talking about. Once you've determined its the motor itself...DONT RUN IT ANY MORE. Its time to pull it and tear it downl

 

[choate]

Its interesting to read advice on this thread and realize only half the folks on this board actually know what they are talking about.

Hahahahahaha yeah

 

[choate]

I hope OP doesn’t have big problems. I gotta admit tho I got a chuckle out of “DONT race my engine”. Screen handle name “racing mason”

 

[gimmie11s]

Exhaust leak

Sorry brotha... pull it out and install fresh gen 2 short block and be done.

 

[sigintel]

Blown

Its interesting to read advice on this thread and realize only half the folks on this board actually know what they are talking about.

Lol right? Video totally sounds like muffler bearings, kaframp stand and benzene ring all hitting each other on cold start. Maybe bad washer fluid?
Thought we were all too gumby to hang on yellowbullet and thats why we are on 6G instead.
At least peeps are trying even if just morale support.
.. could be canooter valve or a bent dinglehopper making that noise too.

 

[racingmason]

Today the weather was in the mid-70s and I was able to use a bore scope on all 8 cylinders but it was hard to see the intricate detail of each cylinder wall. I should know more once the shop lets me use their scan tool to shut down cylinders to further diagnose the issue. I did a compression test again today about an hour after the car was driven 40 miles and all 8 cylinders were above 168 psi. There is some carbon build on the pistons but i was amazed to see the part number, qr code, and arrow pointing to the exhaust side. I will probably order a new short block next week and document the tear down and send everything into Ford for their situation awareness. Maybe it was the luck of the draw with a bad assembly or me being over protective and not beating the piss out of it every single day. Back when I had RX7s and 8s you had to redline them every day to clean the carbon out. I probably would have ended up with the same issue if I just cranked the car up and held it at redline every morning even with 100 psi of oil pressure.

 

[Blown86GT]

Blown

Thought we were all too gumby to hang on yellowbullet and thats why we are on 6G instead.
At least peeps....

Huh?? Translator please?

 

[engineermike]

You could always pull coil trigger or injector signal wires while it’s idling and listen for change.

 

[96gt4.6]

Not advisable on this ecu. You can damage the coil drivers in the pcm doing so, unlike older pcms. Safest way is via scan tool.

 

[engineermike]

Surely you can unplug injectors one by one without hurting anything...

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