One of my friends has a 1995 F-350 with 460. He doesn’t have power brakes until the truck has warmed up 10 to 15 min, then they start working. He has replaced the booster and master cylinder. And still has the problem. Any thoughts

 

Have him ck the vacuum going to the booster from the intake. I’m not sure but I think there is a 460 gas and diesel. If its a diesel then the vacuum pump might not be working, or the vacuum reservoir isn’t holding till the engine is running.<O</O