Serving Our Country!
Join Date: Nov 2007
Location: Austin, TX
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My first inkling is master cylinder. If the master cylinder is leaking by then it is probably able to hold pressure without help of the brake booster (that is, it is able to hold the pressure of your foot only) but when you start the truck and the hydroboost kicks in, the master cylinder can't hold that much pressure and leaks by.
The power steering pump _might_ (or it could be the hydro pump that you hear) be whining louder because the leaking master cylinder is placing additional fluid demand on the system. I would start by replacing the master cylinder.
2002 F-250 Lariat Extended Cab Long Bed, 7.3L, Auto, 4x4
- 6" BDS Suspension lift (All spring)
- 315/75R16 BFG A/Ts
- DP-Tuner F6
- DIESELSITE CPR Fuel System
- Turbo-Master Wastegate Controller
- Donaldson AIS Intake w/ "Zoodad" and AIH Delete
- MBRP 4" T304 Exhaust
- Coolant filter, Evans NPG+ Coolant, 203* Thermostat and Billet Housing
- Factory Tech Valve Body
- ISSPRO Gauges (Boost, Pyro, Trans)