Knock when engine is cold
More Turbo
Joined: Oct 2005
Posts: 560
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From: MICHIGAN
This is just my experience with them.
Your question will most likely spark a debate..
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Often the 5.4 in around those years develope what is called piston slap.
The noise tends to sound a bit hollow.
The skirts of the of one or more pistons get some wear or motor was built a bit on the loose side for tolerences.
When cold, the circular demension shrinks allowing the piston to rock in the bore as it changes direction over top dead center.
Combustion pressure rocks the crown to one side causing the noise.
As the engine heats, the piston skirt expands taking up the excess clearence and quiets down along with oil getting in the area from running.
Usually does not cause any problerms other than the noise we don't like to hear.
Another source can be the timing chains and tensioner so it depends on where you hear the noise when cold.
If timing chain related then you can have an issue later on.
If the noise subsides then don't be to concerned.
Good luck.
The noise tends to sound a bit hollow.
The skirts of the of one or more pistons get some wear or motor was built a bit on the loose side for tolerences.
When cold, the circular demension shrinks allowing the piston to rock in the bore as it changes direction over top dead center.
Combustion pressure rocks the crown to one side causing the noise.
As the engine heats, the piston skirt expands taking up the excess clearence and quiets down along with oil getting in the area from running.
Usually does not cause any problerms other than the noise we don't like to hear.
Another source can be the timing chains and tensioner so it depends on where you hear the noise when cold.
If timing chain related then you can have an issue later on.
If the noise subsides then don't be to concerned.
Good luck.
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khelms_98
1997 - 2006 Expedition & Navigator
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Feb 15, 2006 09:01 PM
