02 GT Engine noise when cold

When cold my 02 GT makes something of a light knocking/rattling under very light load, right at the transition between overrun and driving the back wheels. I know the engine is the source of the noise, not the trans or clutch. It goes away after a minute or two of driving, depending on the engine temperature. It sounds like a light small-end rod knock or possibly a piston slap but it's quite metallic.

I took it to Ford and they returned the car a day later having reprogrammed the PCM and attaching a copy of a Ford TSB #15934, to the workorder. It reads:

"15934: Mustang - Cold Engine light ticking/rattle noise Some 2001-2002 Mustang GT and Bullitt with the TR3650 manual transmission may exhibit a light ticking/rattle noise while driving after a cold engine start. The noise will typically occur between 2200 and 3500RPM under light throttle (1/8 to 1/4 open) while driving. The noise may last a few minutes (depending on temperature). The condition is due to the combination of the light load operation noted above, and the normal piston to cylinder wall clearance present in a cold engine. To service, verify condition and {reprogram PCM...}"

This describes my car to an absolute 'T', right down to the RPM range where it typically occurs (though I've heard it as low as 1500RPM...)

Has anyone else gotten the same report or been referenced to the same TSB? Anything told to you other than, basically, "they all do that...it's normal."?

Only mods: K&N FPIK-II & March UDPs.

-- Mike

Reply to
Mike
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Mike opined in news: snipped-for-privacy@news.golden.net:

Uh... yeah. It's called piston slap.

Certain High Perf Corvette engines have it too. Do a search, you'll see.

Tell you what... my former beater Tbird 3.8 has a Main Bearing knock... and I put 50,000 miles on it like that. And that's a LOT worse condition than piston slap.

If you are worried use Mobil 1

Reply to
Backyard Mechanic

This is piston slap and is normal and expected with forged pistons. Forged pistons expand significantly when heated and thus must be undersized when cold. When cold, they have a little extra room to bounce around in the cylinder and produce the slap you hear. Once they heat up they expand to the correct size (correct piston to cylinder clearance) and the noise goes away.

If you they were fitted to the specified piston to cylinder clearance when cold, they would expand and seize in the cylinders when hot.. a very bad thing. So go forth in good cheer.. everything is right with your engine.. if not the World.

I would recommend NOT getting on your engine until the pistons are fully heated and the piston slap goes away. This is good practice even if you dot have piston slap.

LJH

95GT

Reply to
Larry Hepinstall

I don't believe the 02 GT 4.6L 2V motor has forged pistons, does it?

At any rate, it's a "disappointing" noise but the motor is healthy power-wise and it does go away after a while. I do tend to short shift and light-load it till it's warm too.

I was hoping that someone who'd heard this exact noise from their GT would chime in. Why does Ford limit the TSB to only some 2001-2002 GTs? A batch of ill-fitting pistons?

Thanks, Mike

Reply to
Mike

It's not "disappointing" if its intended to be that way. I put forged pistons in my 331 and I expected to hear piston slap when the engine was cold (and I most definitely do). That is the ONLY way it can work correctly.

If the piston slap goes away when the pistons heat up that means the pistons are expanding correctly. My GUESS is that you have forged pistons. If they weren't forged, I doubt they would expand enough to eliminate the piston slap. Hopefully someone will know what kind of pistons your engine has.

LJH

95GT

I do tend to short shift

Reply to
Larry Hepinstall

No forged pistons in 4.6 2v motors, they are the hyperpathetic varity and also have piston slap issues. Here is some info I found on the web; Hyper-Eutectic pistons, "hyper" meaning high and "eutectic" meaning melting point are cast with a special material ( high silicate level about 12 or 14 %, the max before the metal sweats it out) at a higher temperature than normally used in the manufacturing process. The result is a light piston having nearly the strength as a forged piston combined with the desired hardness and low expansion rates of a typical cast piston.

Reply to
Mike King

correct, they have hypereutectic (sp?) pistons , not forged.

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Reply to
Rein

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Rein

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