Ford Repair: Engine Knocking, oil pressure, lifters

Question
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Followup To
Question -
I have a F350 5.4 2000 gas engine at the store I manage, It may be a different year. A few days ago the engine started knocking we checked the oil it was very low. We had the oil change and it still knocks. The sound stops after a couple of minutes. It holds the oil pressure and runs very smooth after the couple of minutes. Any idea what may have happened.   
Answer -
Hello and thanks for the question...I'll try to help.
 What I would suggest to you is that you check the antifreeze level, and if it's low, I would attempt to find out where it's leaking in to or out of. Also, is the noise a low sounding "knock"? Or is it more along the lines of the lifters tapping?
Thanks,
Erik


The ticking noise sounds like a loud clock it ticks more frequently the more rpms the engine is pulling.  It is prutty loud for a knock but not extremly loud.  It may last up to a half mile to a mile and then goes away and will not reappear until the engine has cooled.  The dealer I took it too said the engine needed to be replaced, everyone I have talked to said if the engine had gone bad the noise would be constant and the oil pressure would vary, it doesnt.

Answer
Hello and thanks for the reply...I'll try to help.
 It's difficult to say, with out listening to the engine myself. BUT, there are a few things to take in to account....
The engine oil was low, as you've said.
There is a "knock", that has just started, and dissipates as the engine runs for 2-5 minutes.
A dealership, has told you the engine needs to be replaced.
What I would suggest is that you bring it to a different dealership and see if they agree with the previous one.
The reaction should be the same.....
Hope this helps,
Erik