Ok 06 5.9 just turned 70K and I am getting a strange clunk sound. It almost almost sounds like metal expanding or contracting. At first I thought suspension but it does while sitting still. My wife says she can feel it on the floor board on the passenger side I can't hear it or while under power but the sound is becoming more frequent. I crawled around underneath and poked at this and that but didn't find anything loose or binding. Any ideas???? I am thinking exhaust but it doesn't make sense why it would do it fully warm or cold.

 

Prob not it but is there any chance it might be the A/C pump cycling?

 

I did a search and came up with that same question. I usually leave the selector on defrost which would make the a/c cycle so I moved the selector and whadda you know it stopped. Now my next question what to o to fix it ????

 

Neat!!! At least you narrowed it down. You might want to make another post about A/C making a thumping noise when kicking on or somthing like that and see if any DTR members have the same problem. Sorry that I cant help since I am pretty mechanicaly inept and my A/C does not make any discernible noise from inside the cab. I did find a couple of links after typing in A/C noise in the advanced search. Hope they help. https://www.dieseltruckresource.com/...ht=A%2FC+noise
https://www.dieseltruckresource.com/...ht=A%2FC+noise

 

The ac clutch is metal to metal. After a while the two surfaces get rough from rust.

Dont worry about it. Wont hurt nothing.

Carey