Hello. I have a 99 F-150 S/C, 4.6 Romeo, 2WD, 3.55LS, Auto, 14,600 miles. I use Mobil 1 5w-30 since the truck had 12,000 miles and have always used Motorcraft oil filters.

The other day after running down the interstate for about 3 hours, I noticed a tapping sound from the passanger side of the truck (with the truck at idle).

I turned the wheels to the left so I could better hear the noise from the passanger fender well. It sounds like it is coming from just above the exhaust manifold near the rear of the engine (I know it is not fuel injectors--the frequency of the tapping is too slow). I listened to the other side of the engine and there is no tapping. It doesn't make this noise when cold.

Here are my questions: Is this normal? Should I have it checked out? Anybody else experiencing this?

Thanks for your attention!

 

SRB,

I had a knock, similar to what you described when the engine was warm in my 5.4. It didn't have it all the time, but it was cause for concern all the same. My engine was replaced for piston slap. I don't have that sound in the new motor. I'm not sure if it's related to piston slap, but I would have the dealer listen to it. At the very least they'll have it on record that you complained about it.

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99 XLT Black Ex-cab, Flareside, 5.4, ORP, 3.73, Gibson Supertruck, K&N, Superchip, Raised front 1", Modified Airbox, Slap-Free Motor at @19k