I have a 2005 2500 Diesel Ram. Starting about 2 months ago I started having a problem where the brake pedal is very hard to push, but only when it is all the way out. Once it is pushed in about ½ of an inch it works normally. If I don’t let the brake pedal come all the way out I don’t have problems.
Any ideas on what this could be? I don’t want to take it to the dealership if I can help it.
Thanks for any help.

 

Welcome to the site.

I will move this over to the CTD section but first keep in mind a diesel doesnt have a vacuum booster for brakes. It uses a hydro boost which is driven off the PS pump and uses ATF4 fluids.

So my Qs would be is your power steering ok and have you checked the fluid level? After that I would question the linkage from the brake pedal to the inside of the hydro boost and then after that question the functions of the hydro boost itself.

 

Try bleeding the brakes and see what happens