My dad has a 2002 FX4 with the 5.4L and is experiencing a loud knock when the engine is cold and continues to knock for about 10 min until the engine is warm. The knock is so loud you can hear it from the house when the truck is idling. Any ideas or suggestions?

 

Hi

I suggest that you suggest to your Dad Take it back to Ford and get their opinion, then let us know. Hopefully its under warranty, if not, keep reading the knockers/pingers/clickers here that are seeking answers/fixes/no fixes etc.

Meantime you may get more meaningful info. from others here.

Good luck...OT

 

That is kinda strange. Even when it is -50F my truck doesn't knock real loud. What temperature is it outside when the truck does start to knock?

 

It's called piston slap!

I had a 2001 F-150 last Winter that knocked so loud that you would have thought someone was hitting the block with a hammer. Whenever I left it at the dealer overnight so that they could hear the knock, it wouldn't get cold enough to make any noise. It quit knocking after a few months and I've traded it in since then.

 

It was no colder than -10C overnight. I have heard of the piston slap problem and he is taking it to the dealer next week.

 

Piston slap seems to plagueing a lot of engines now a days. It is not just Ford engines that are experiencing this, but Chevy, Honda, Toyota, and most other makes that are also having cold start knock problems. My truck doesn't do it and I am kinda glad it doesn't (hoping it never does have it).

 

My 99 5.4L has done it (although I don't think I can hear it inside the house) for 60k miles and there don't seem to be any issues. I mentioned it to the dealer once an they changes the serp belt. Still does it. Oh, well, performance does not seem to be affected and everything else looks fine.

 

It's definitely the piston slap problem.

Ford was replacing engines due to that about a year ago. I haven't kept up with it lately though. The problem I saw was Ford was replacing the engines with rebuilt motors, not new ones.

 

Will the weight of engine oil used help reduce or eliminate piston slap? In other words, would a thicker oil stick to cylinder walls and help reduce noise, or possibly a thinner oil that will circulate through engine quicker help quiet noise?

 

I doubt it, the problem is the cylinder and piston size. There is enough slack between the two that is slaps when cold. The piston expands enough when heated that it finally stops. There is quite a bit of info on it on this site if you want to read up on it.

RickC

 

I've got an 03 with 3500 miles on it that does the same thing. It was just in the shop yesterday and they were basically clueless. I'm taking it to another dealership after the holidays. They tried to tell me that the problem was that there was a body plug missing out of the firewall from having the alarm installed!