Fan and noise

[Liberty&Justice4All]

My fan seems to come on every time I start the engine no matter what. Any ideas? I also have a noise that sounds like a knock but it’s not a rod or piston I don’t think, it is not consistent. It seems to do it when taking off more than any other time. Any ideas?

 

[tommudd]

Noise could be a 100 different things, need better description, where does sound come from, in gear or in neutral, moving or sitting still etc
Taking off as in moving forward or reverse or both , at what speed , narrow it down some

 

[LibertyTC]

Do you have the HD cooling with viscous fan & electric fan?
The knock, when taking off, does the engine hesitate or is running smoothly?
Any engine light on/codes?

Please add 2007 KJ to your signature line THX.

 

[Liberty&Justice4All]

No codes, when taking Off in reverse and drive. You can only hear it in the vehicle not outside. Maybe something with exhaust? Cause can hear it or something similar out the pipe. Does it have a flapper at exhaust manifold and tubing? Runs good and smooth. Electric fan on it.