I have a 06 f250 6.0 and a month ago all of a sudden, I had power steering issues and brake issues. I flushed the system and replaced with Mobil one and had no problems since. But... When I apply my brakes, the pedal is very sticky at the top and then after the stickiness the pedal is fine. I can apply the brakes and they don't go to the floor, they seem solid. Another clue is that my AC now sometimes only blow out the defrost. Vacuum pump???. Would the vacuum pump cause my brake pedal to be sticky like that? I've sprayed wd40 up around the linkage with on change. What's next? Thanks

 

The vacuum pump is not tied into the brake system. I have not dealt with this myself but sounds like your power steering pump problem is back as this pump also powers the brakes.

You do have a vacuum problem. Turn the key on, do you hear the pump running? IF not pull the vacuum hose off the pump and see if it comes on. If not it is the pump. If the pump is working you likely have a leak somewhere.

Is your truck a 4x4? Most vacuum leaks I have ran down seem to be related to the 4 wheel drive. The other common on is the vacuum line on the heater line running on the passenger side. There is a vacuum line on the valve that stops coolant flow to the heater core when the AC is put on high. This line often falls down into the engine compartment so it is not noticed.

 

Fixed vacuum leak. It was just a line that came off. Easy. The brake pedal is still really sticky. Master cylinder or something else ???.