The shop has installed , new steel lines , new master cylender , new booster , and new vacuum pump . The lineings , roters , and drums are all fine . The cummins is in good condition ( 103,000 ) miles , I am the original owner .
1. Has the system been well bleed after replacing the lines?
2. Does the power boost work properly... If the pushrod on the bosster isn't checked and adjusted if needed it will cause problems.
Pump the pedal a few times hard to relieve any stored vacumn, then with your foot on the pedal start the engine and the force of the booster should lower the pedal. If this doesn't happen the booster and/or vacumn pump aren't working correctly.