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I'd imagine your brakes are boosted by the PS unit too. Soooo. | +1 Diesels have no intake vacuum, thus they must have Air, or Hydra-boost brakes, and I've not seen a F-series with OEM air brakes. |
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Diesel engines may not have intake vacuum, but it has not been uncommon for them to be equipped with vacuum pumps to provide vacuum for various accessories including vacuum powered brake boosters.
That being said, I believe that a 1999 Ford Superduty should have a HydroBoost hydraulic brake booster that does operate off of the power steering system. They also have a vacuum pump. |
what''s the difference between Hydroboost and a vacuum system? i have both chevy and ford diesels; the gm having a vacuum pump, but i forget. |
Vacuum assisted brake boosters basically use vacuum, either from intake manifold vacuum or an auxilliary vacuum pump, to create a low pressure environment inside of the brake booster canister. When the brake pedal is depressed, it allows air at normal atmospheric pressure to enter one side which then acts upon a diaphragm and presses it towards the other side of the booster which still has vacuum in it. This force is transmitted to the rod that goes to the master cylinder.
Hydroboost is a brake booster that adds supplemental pressure to the braking system via pressurized fluid from the power steering pump. Fluid flows from the power steering pump, through the booster, and then onto the steering box. When the brake pedal is not in use, fluid flows through the booster to the steering box. When the brake pedal is depressed, pressurized fluid flows through a spool valve into a chamber in the booster. This fluid exerts a force on a piston in the unit which pushes on the master cylinder and provides assist to the brakes.
Hydroboost systems provide roughly twice as much pressure to the brake system as do vacuum boosters. This means that the brake calipers and wheel cylinders are able to exert that much more force and provide better stopping power. Hydroboost is pretty much universally considered to be better than vacuum boosters.
I know that GM has used Hydroboost systems on their heavier duty light trucks for a long time. Our 1994 GM K2500 Suburban had a Hydroboost system on it.
Dodge used vacuum boosters powered by vacuum pumps in their diesel trucks though the 1996 model year. My 1997 Ram with the Cummins turbo-diesel has a Hydroboost brake booster along with a vacuum pump that operates the heater/AC controls, cruise control, front axle disconnect, and exhaust brake.