I am new here and have done a search with no luck. A few days ago that when I turn I am getting a hissing noise at the drivers side firewall when I turn the steering wheel but it goes away when I step in the brake. Has anyone ever had this issue and if so what was it that was causing it? I have checked the powersteering and brake fluid and they are both fine. Any suggestions would be great. Thanks

 

I think you could possibly have water in your power steering fluid. Especially if you have washed your engine down and not cover the filler cap.
Do a search, for there is a link on how to flush the P.S.
I followed the link and then added some lucas PS additive and a little driving and it all went away. Some one will jump in here with some input. I am assuming it is a diesel.

 

Here is an article that Guzzle put together.
You can find the PS flush down the page a bit.


Powerstroke Mods and Maintenance