I have been looking over all the replies and see reports that are not consistant with the term piston slap as it has been known for many years.
My understanding and experience is piston slap is the excessive piston skirt clearence allowing the piston to rock in it's bore.
This clearence condition is influenced by the piston metal alloy expansion rates as well as the cylinder diameter expansion rate.
The replies that don't fit this action are the ones that:
go away in 10 seconds, go away with an oil change, only happen in cold weather, comes and goes and a bunch of other sineros.
The true piston slap will indeed be there all the time because the condition never changes, will or should reduce when the engine comes up to operating temp, may be somewhat sensitive to oil viscisity as a cushion.
While indeed there may be engines with noise from various other sources, not everyone here does have piston slap.
Quality is job one has more to do with the vendors supplying the parts in tolerence and the bore machining tolerence than it does with engineering.
Not on every assembly does the piston clearence end up being perfect but within a tolerence range. If this tolerence range gets out of hand due to quality control then there is high posiblity of noise.
I'm not defending Ford but only to try to bring forth that not all the noises heard are a result of piston slap as defined above.
So the end result at the dealerships is games played and stalling because unless the engine is dissasembled and measurements taken will the real truth be known on each case. So you know Ford or no other mfger will go to those lengths.
The old way of determining what cylinder had piston slap was to disable the ignition to each cylinder and observe the noise change. Sometimes it was a rod brearing that makes nearly the same noise in some engine designs.
Years ago in the 70s the engines that developed piston slap at high milage could be detected easly and if kept on using these engines that banged hard full time, the risk was quite high to lose the engine altogather because the piston shirt broke up and let the rod bang around in the cylinder which ruioned the block and crank. Todays piston designs almost never reach that point because of improve design and metal alloy compositions.
So to close this out, not every tick and noise is piston slap once it is understood how and why piston slap is produced.
I think from the comments about the noises heard and how they act at least 90% donot have piston slap but other noise sources.
There is little reason for a dealer to spend huge amounts of time to find noise sources unless there is prior knowledge on what to look for and an official way to handle it. It is at this point that the fighting begins when the situation cannot be pinned down to an absolute.
As has been said: replacement engines also had the same noise. Question is, was it piston slap indeed or is it something else?

 

What weight and brand oil did/do you use? What brand oil filter? Do you have a factory oil cooler? Do you have the remote oil filter mount? Do you or have you driven it hard before it is fully warmed up? Do you drive pedal to the metal often and if so, how many gears do you go through at full throttle? Do you have a manual or automatic?

My '98 did it in the winter too. It quieted down after warmup but I always heard one cyl. though light on the highway. The wife couldn't hear it. I bought a new engine from Roush Industries to change it out but never got it done before I traded it. I still have the engine if you want to change yours out. I think a lot has to do with care. I also believe a lot has to do with the materials and dimensionals of the 5.4 with the long stroke and piston materials. There is also much more to be said for the use of the 5/20 synthetic blend for more than just flowability and gas mileage but also lubrication. That 5/20 will do more for lubrication of the upper cylinder and piston skirts and pin than the 5/30 could.

 

interesting, I've got a 2000 with a 5.4 and it sounds a lot like a diesel when the engine is cool and the sound tends go go away once the engine is warmed up. I may have to take it in and see what's up since I bought an extended warantee with it

 

What weight and brand oil did/do you use? What brand oil filter? Do you have a factory oil cooler? Do you have the remote oil filter mount? Do you or have you driven it hard before it is fully warmed up? Do you drive pedal to the metal often and if so, how many gears do you go through at full throttle? Do you have a manual or automatic?

My '98 did it in the winter too. It quieted down after warmup but I always heard one cyl. though light on the highway. The wife couldn't hear it. I bought a new engine from Roush Industries to change it out but never got it done before I traded it. I still have the engine if you want to change yours out. I think a lot has to do with care. I also believe a lot has to do with the materials and dimensionals of the 5.4 with the long stroke and piston materials. There is also much more to be said for the use of the 5/20 synthetic blend for more than just flowability and gas mileage but also lubrication. That 5/20 will do more for lubrication of the upper cylinder and piston skirts and pin than the 5/30 could.

 

Granted, many people are jumping on the bandwagon for piston slap and a few may not have it but I refuse to believe with all of the history and data gathered that Ford did not know what it was. I work for another major manufacturer and they do the root cause analysis and engineering changes to correct deficiencies.

Also, piston slap can disappear with temperature rise of the engine and ambient air temp. Keep in mind that the linear expansion per unit length per deg. F for aluminum is 0.00001244 while for cast iron it is only 0.00000655. Assuming that a cylinder wall is running at 300 deg that means that their is only 0.001508" growth while the piston running an assumed 400 deg grows 0.0041168" This is assuming that they are running at temps that close together. I have not done the calculations for circumferential growth but as you can see, the warmer the engine, the tighter the clearances become.

I also happen to be a Supplier Quality Engineer and I fully understand what you are saying about suppliers maintaining control on tolerance allowances, but I think you will find that it is much closer than you believe. Unless of course, that supplier is one who has no business being in the industry.

As I said before, I could still hear one cyl on my engine rapping albeit lightly at operating temperature. I dreaded winter and the increased noise level.

Regarding your comment, "There is little reason for a dealer to spend huge amounts of time to find noise sources unless there is prior knowledge on what to look for and an official way to handle it.", it is the dealer's responsibility to respond to a customer complaint. If that means digging into an engine to find the root cause, then so be it. If the dealer never spends any time finding the sources, how will they ever develop "prior knowledge" and the historical database. I firmly believe Ford knows what the problem was but acknowledgement could have been very expensive.

I don't know why Ford cannot make an engine as quiet as GM or Toyota. I love Ford but I get stressed every time I hear or rather don't hear the compitition's engines.

 

No I Baby my truck ,,never pedal to the medal and always make sure it is warmed up.Do you work for ford? Spend 20 grand on a truck and see if u say that when your truck is knocking. Ive always use the ford house on oil changes,,they know the problem is there ,,but want to too b.s. ,, like you

 

No, I don't work for Ford, but I do work for another fortune 500 company. As a Quality Engineer I am just asking questions that I would need to ask for a better idea of what is going on. I spent more than that on my '98 and at the end of July I traded it in on an '05 and spent more than that again. I too am concerned because my '98 did it and I bought a new engine for it. Unfortunately, I never got it changed out. I still have the engine if you are interested. Now I have the '05 and I find it is much too noisy for my taste. Why they cannot make an engine as quiet as GM or Toyota I don't know. I don't use Ford for oil changes but do use their oil filter from Walmart, $3 vs. about $7 at Ford. I also am careful about the quality of oil I use.