Piston slap? (general)

[msnunes]

Could someone please describe the symptoms of "piston slap" as described on other threads? Is this the same as a 1-2 second (or more) knock I hear on cold start-up, or something else?

Does it occur only at start-up or at other times? Is is caused by lack of lubrication high in the engine? (read a reference to someone solving their problem by changing to a filter that wouldn't allow oil drain-back...)

I've had this symptom for as long as I can remember in my '87 302, mostly in the winter time on cold start-ups, and always wondered what exactly it was -- either piston wear or lack of lube or both (and I've run with Amsoil for the last 95K!). I have found, though, that engine oil additives (Prolong, Duralube, etc) will take care of it in the short term (they only last 3-4000 miles or so). Unfortunately, use of those additives destroys the longevity of Amsoil, defeats my purpose for using it, and shortens its life significantly (as my periodic oil test results show). Nonetheless, if it really bothers you, an extra $20 bottle of something can make it go away during the cold weather months...

Thanks.

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Soon to buy: 4x4 Quigley E350 - V10 or PSD???

[KXHauler]

There are alot of causes for noises that sound like piston slap.. The 'piston slap' that is most talked about occured on 5.4L (some 4.6 and some V10s) between 1997 and 4/99.

The cause for this particular version of piston slap was pistons from a particular supplier were sometimes out of tolerance.
This had nothing to do with lack of lubrication.

The symptom occured mostly at startup on cold mornings, and would last from 2 to 30 seconds. The sound is a loud fast knocking, like shaking marbles in a can.

Of course there are other versions of piston slap that can exist in the world for a variety of reasons, and can occur on any engine..

The first thing to do is check your oil filter..

A common problem that is sometimes mis-diagnosed as piston slap is the Ford Triton engines (and other ford engines) require that you use an oil filter with and anti-drain back valve (filters with an S on the end), which keeps the oil in the top end.. IF you don't use the correct filter, when the truck sits, the oil drains down, then on startup you get some knocking until the oil hits the top end.

On the engine your referring to, the cause for your noise is probably different than the piston slap topic you hear alot of folks talk about.

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00 F250 XLT SC 4x2 5.4L 5sp 4.10LS

[88F250]

Its been too long for me to remember wheather piston slap was the bright hi pitched crack or the dull thud, but in either case, you can smoke it out by letting it Idle as low as possible, and short out a Plug.
If you get the crack or thud, then you got a little slap in that cylinder.
You probably know that if you have piston slap you probably have a lot of blow by and therefore a dirty air filter and black carboned up plugs.

I once had a 300, I-6 that made a loud clicking and pounding noise on startup. Just a few seconds till the oil pressure got up.
Amsoil wont help you there. Go back to real oil of the 10w50 or 20w50 and see if it slows or stops the noise. If it does diminish the noise, you have bearings going out! And a big decision to make.

[NoMo]

Search the engine forum archives at www.f150online.com for more than you care to know about piston slap. There is even a .wav file of "the slap".

[88F250]

Thanks to KXHauler and MOMO for two good tips. I'll remember that Oil Filter "S" when I get a chance to take a close look.

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Hoppy's Rebuilt 88-F250 7.3, C-6, 410 gears, ex-cab