Hydroboost/Hydraulic brake booster

What is Hydraulic brake booster (Hydro-booster) ?

Hydroboost brake units use power steering pressure instead of engine vacuum for brake assist. This is sometimes necessary if the engine does not create enough vacuum to assist the braking system. This is true for diesel, turbocharged, and supercharged engines. Some manufacturer's use an engine driven vacuum pump to operate the vacuum booster instead of a installing a hydroboost brake system.

A hydroboost unit is located between the firewall and the master cylinder, just like a vacuum booster. It has hydraulic lines leading from the power steering pump to the power steering gear, much like the lines incorporated into the power steering system. It uses a spool valve and power piston to regulate pressure. A spring loaded or nitrogen gas charged accumulator is used in case of a power steering system failure.

What kind of vehicles will the Hydro-booster fits to?

Usually some  Pick-up, Light truck , Forklift in USA market use this kind of hydroboost instead of traditional vacuum boosters, like some GM ,Ford light truck, Pick-up, Bus etc.