whiteeye42

hi i have a friend that has a 04 5.9 cummins and is having problems with the vacumn pump he had the pump replaced but the cruise control still will not stay enguaged he wants to know what all the vacumn pump controls and were he might look for a vacumn leak or what eles might be wrong with the cruise control Thanks in advance

infidel

Easy way to tell if there is a vacuum leak is after running the engine shut down for five minutes then disconnect any vacuum hose.
It should hiss.
A system without leaks will hold vacuum for hours if not days.

Second most common cruise problem behind vacuum problems is a bad brake light switch. The switch has several sets of contacts, the brake lights can work fine but another set of contacts not.

whiteeye42

ok thanks i will tell him to check the brake switch

Russ Roth

I believe the cruise on an '04 is completely electronic with no vacuum involved.