Need assistanced diagnosing engine noise
06-22-2004, 01:02 PM
#1
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Need assistanced diagnosing engine noise
Yep, Im asking for opinions. Im pretty sure I know what the problem is, but I figured I'd do a little desktop diagnosis for conversation.
The problem: Engine noise (sounds like little monkeys with a hammers beating on the top end) that comes and goes based on rpm, load, and engine temp. Sounds to me like a wrist pin problem or piston slap. The Cobra engine is supercharged, its a 96. Mileage is 64k.
Its not bottom end noise, and is coming from the back passenger side cylinder. Before I got there and looked at it I was hoping for a broken rocker arm or something in the head. I really can't see a top end head noise varying with load.
Any takers? I would just tear it down but I'm not gonna be able to work on it for at least a few weeks, I have two other engine jobs ahead of it in my garage.
The problem: Engine noise (sounds like little monkeys with a hammers beating on the top end) that comes and goes based on rpm, load, and engine temp. Sounds to me like a wrist pin problem or piston slap. The Cobra engine is supercharged, its a 96. Mileage is 64k.
Its not bottom end noise, and is coming from the back passenger side cylinder. Before I got there and looked at it I was hoping for a broken rocker arm or something in the head. I really can't see a top end head noise varying with load.
Any takers? I would just tear it down but I'm not gonna be able to work on it for at least a few weeks, I have two other engine jobs ahead of it in my garage.
06-22-2004, 03:53 PM
#2
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Join Date: Apr 2004
Location: Florida
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RE: Need assistanced diagnosing engine noise
its definitally monekys you better get in there and get that f**ker. lol. nah i couldnt tell yah what its is. hope its not abig deal. your wife was braggin about killin your GT in that thing lol. dont make it to fast. good luck
06-22-2004, 06:35 PM
#3
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RE: Need assistanced diagnosing engine noise
Windsor plant motors equipped in many of Ford's Trucks/SUV's & Mustangs experienced nasty piston slap at start-up and would eventually go away when engine temperatures came up. Very few people experienced anymore slap after warm-up. I'm pretty sure those older Cobra motors were hand built by SVT..
Piston slap usually sound erratic (spelling) It isn't always creating noise in a rhythm, sounds like it's just kinda floating around in there hitting whatever the hell it wants.
BUT, before the motor died in my 88 Iroc-z, I had some nasty piston slap occuring, if I eased into the throttle and eventually went WOT I heard nothing. If I downshifted and put it to the floor, it sounded like she was ready to violate my oil pan.
I also had a nasty case of piston slap in my 02 GT that required a replacement short block... ****ty luck eh?
The idea of a wrist pin getting ready to let go is scary. It can make a mess of that block real quick, although when we had a failure in our small block modified, it sounded like it was a top end problem, until we stuck a steth to the block and oil pan. If it's not causing any driveability problems or lack of power, I'm gonna say you hit this one right on the head!!!
Piston slap usually sound erratic (spelling) It isn't always creating noise in a rhythm, sounds like it's just kinda floating around in there hitting whatever the hell it wants.
BUT, before the motor died in my 88 Iroc-z, I had some nasty piston slap occuring, if I eased into the throttle and eventually went WOT I heard nothing. If I downshifted and put it to the floor, it sounded like she was ready to violate my oil pan.
I also had a nasty case of piston slap in my 02 GT that required a replacement short block... ****ty luck eh?
The idea of a wrist pin getting ready to let go is scary. It can make a mess of that block real quick, although when we had a failure in our small block modified, it sounded like it was a top end problem, until we stuck a steth to the block and oil pan. If it's not causing any driveability problems or lack of power, I'm gonna say you hit this one right on the head!!!
06-22-2004, 06:40 PM
#4
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RE: Need assistanced diagnosing engine noise
Correct, there is no drivability problems or power loss - other than from running rich and retarted since it has a blower tune and the blower is in the trunk, courtesy of the former owner who thought the problem was a knocking blower unit. I'm planning on removing the valve cover on that side when I get a chance, and if I find nothing there then out comes the engine.
06-22-2004, 08:15 PM
#5
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RE: Need assistanced diagnosing engine noise
Md, im only 19 and you can take this advise if you' like. But i wanna whack the donkey with a stick too. 
I'd take a stethoscope and put it to youre head. Valves more so. Ford put out a TSB on this issue i can email you the info if you'd like. Its a TSB on all 32 valve DOHC motors to date. Its especially noisy at idle. And it comes from the passengers side rear of the head. Just my 2 cents. I hope it helped.
I'd take a stethoscope and put it to youre head. Valves more so. Ford put out a TSB on this issue i can email you the info if you'd like. Its a TSB on all 32 valve DOHC motors to date. Its especially noisy at idle. And it comes from the passengers side rear of the head. Just my 2 cents. I hope it helped.
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