Well, One month ago I bought a 1999 supercab 4x4 with 57630 on the engine. When I test drove it before I bought I did not hear a knock in the engine. I bought the truck and drove it home and the next morning I woke up went out and started the engine and I heard a pronoced knock. I called where I bought it and brought it back and they said bring it in. When I went to pick it up the service manager said they put an additive in the motor and it would go away after 700 miles of driving and I believed him. It has not been 700 miles yet, but it is still making the knock on startup and continues
to make it even when the engine is hot. One week ago I learned of this site and read a lot of the posts on Piston Slap (ps) and this made me fell a lot better because no one has lost a engine from this. I keep reading and another post tells me about outside temperture has a lot to do with the expansion of the block. Some where over 50 degrees outside temp. and the Knock might not be there. Now I read (I have the 5.4 engine) Something about the spark plugs might go fllying when I hear when the engine starts making weird noises. Anyone have any comment?

 

The Piston Slap issue you are referring to generally only occurs in cold mornings, and it goes away relatively soon. If your engine is knocking all the time, I would say you have another problem.

I would be leary of an additive fixing the problem...especially taking 700 miles.

 

any chance you have put 300 miles or more on it since purchase?
I can say I knew a dealer that would give the ol "itll be ok in a thousand mile" or "Itll take a while for the new parts to break in" routine.

That was just enough miles that the sale could not be undone. Just beware thats all im saying.

 

Tatal and complete BS!!! Take the truck back and tell them that you DO NOT want it back until you have two things:

1. An absolute diagnisis of what is making the noise (NO GUESS' alowed)
2. An absolute fix of the above absolute diagnosis.

If either is not met give the truck back. Do not take the BS answers!

Good luck-

 

I completely agree with HCMG don't fool with them I would make them take the truck back 5.4 mod. motors don't have piston slap that is a GM problem but your yr. does have a spark plug problem and it may have already blown a plug and they have made a hokie repair also ford recommends that no additives be put in the oil!!!

 

Sounds like piston slap to me. Both Ford and GM have this problem with the 5.4 being the worst for Ford and the 5.3 being the worst with GM. Piston slap is a minor rocking of the piston in its bore because of loose skirt to cylinder wall clearances which tighten up as the engine warms. Piston slap will probably never cause any problems as in a failure, but the diesel knock like sound is embarrassing as hell. I would take it back and make them accurately diagnose and fix whatever the problem may be or give you another truck.

 

Heres a link from this site: https://www.f150online.com/forums/sh...ht=piston+slap