Nissan 2. 40sx Performance, Modification, Repair and DIY Articles. NICOclub. They are independent publications and are not affiliated with or endorsed by Nissan Motor Company or Nissan North America. Information Copyright 2. NICOclub All rights reserved Material may not be distributed without written permission. If youd like to use one of these articles on your site, please contact webmasternicoclub. Hydro Boost Power Assist Systems Operation Diagnosis and Repair. Hydro boost power assist was introduced in 1. Bendix as an alternative to the vacuum booster. At times, the hydraulic pump units may also be referred to as the hydraulic power packs, hydraulic power pack units or hydraulic power units. They all refer to the. R50R53 Mini Cooper. Comment Installer Un Serveur De Messagerie Sous Linux. Power Steering Pump Fan Duct. Replacement and Installation. The power steering pump and fan are known issues with our Mini Coopers. Nissan 240sx performance, modifications, maintenance, repair, diagnostic and howto articles. The hydro boost uses the hydraulic pressure from the power steering system to provide the driver assist in applying the brakes. There are three reasons why a vehicle may be equipped with hydro boost instead of a vacuum booster. There is no vacuum source available, as in diesel engines, or the vacuum source available is too weak to adequately supply a vacuum booster. There is limited space available for the power assist device. The vehicle requires more assist than is available from a vacuum booster. Hydro boost has been used on a variety of vehicles since its introduction and OEM applications presently include 1. Cobras and all V8 Mustang. Most 2. 50. 0 and 3. GMCChevy trucks Dodge Ram equipped with Cummins turbo diesel. Shop from the worlds largest selection and best deals for Other Business Industrial Equipment. Shop with confidence on eBay Pneumatic Vacuum Elevators are the newest thing in elevating. Vacuum elevators use no cables or pulleys but use a vacuum to lift the cab. Buy Proform 68110 at JEGS Proform Air Pump Idler Bracket for Ford Mustang 302 351W. Guaranteed lowest priceFord Super Duty series trucks equipped with Diesel and. All Hummers including the H2. Proper diagnosis of hydro boost related problems requires an understanding of how the system works. A typical hydro boost is shown in Figure 1. The hydro boost is plumbed in line with the steering gear. Power Brake Vacuum Pump Installation' title='Power Brake Vacuum Pump Installation' />The power steering pump supplies pressurized fluid for both the power steering gear and hydro boost. Spool Valve. Fluid flow in and out of the hydro boost is controlled by what is known as a spool valve. Spool valves are used in a variety of hydraulic components, such as the valve body of an automatic transmission. A spool valve is basically a hollow cylinder with a number of rings machined into it see Figure 2. The surface of the spool valve is highly polished to form a sealing surface. The raised portions of the cylinder are called lands while the indentations are called annular grooves. Figure 3 shows a simplified spool valve positioned in a bore with three ports. The path of the pressurized fluid from port 1 is determined by the position of the spool valve. The spool valve is positioned in figure 4 to allow fluid flow from port 1 to port 2 while port 3 is blocked by land 1. Figure 4 shows the spool valve moved to the left which changes the fluid flow. The fluid flow is now from port 1 to port 3 with port 2 being blocked by land 2. The spool valve in a hydro boost works in a similar fashion. Hydro boost Construction. Figure 5 shows a cutaway of a hydro boost with all the major components labeled. These include the housing, power chamber, input rod assembly, a lever assembly, a power piston, spool valve assembly and an output rod. The housing is fitted with three ports as identified in Figure 6. The spool valve fits into a precisely machined bore that is part of the hydro boost housing as shown in Figure 7. The fit between the spool valve and the bore is such that it creates a seal while at the same time allowing enough fluid between the lands and bore to provide lubrication. The spool valves position is determined by the lever assembly which is connected to the input rod. Pedal Unapplied. When the brakes are unapplied the spool valve is positioned as shown in Figure 8. In this position the pressurized fluid from the power steering pump is allowed to flow to the steering gear, but not into the power chamber. The spool valve vents the power chamber to the return line of the power steering pump reservoir. Pedal Applied. Once the brake is applied, the input rod moves forward left to the power piston assembly. The piston return spring is preventing the power piston and pin A from moving forward. This lack of movement causes the input rod to force the travel limiter valve assembly into the power piston which results in pin B moving forward. The lack of movement at pin A and forward movement of pin B causes the lever to pivot at pin A. The top of the lever moves forward left which results in moving the spool valve See Figure 9. The forward movement of the spool valve closes the reservoir port which seals off the power chamber. Continued movement of the spool valve opens the pressure port from the power steering pump allowing pressurized fluid into the power chamber while at the same time maintaining the fluid flow to the steering gear. The pressure in the power chamber causes the power piston to move forward left which applies the brakes through the output rod See Figure 1. Pedal Released. Once the brakes are released, the spool valve return spring pushes the spool valve back to its rest position. This vents the pressure in the power chamber to the power steering pump reservoir through the return line. The power piston and lever assembly are returned to their rest position by return springs which in turn brings the brake pedal back to an unapplied position. Back Up. Similar to the vacuum booster, the hydro boost is equipped with a backup or reserve in case the source of pressurized fluid is lost. A failure in the power steering system, such as a broken hose, broken power steering pump drive belt, or failed pump, would result in a loss of pressure to both the hydro boost and steering gear. The hydro boost uses a high pressure accumulator to store power steering fluid under pressure in the event of a failure. There are two types of accumulators used, some hydro boost units use an external accumulator, while others incorporate the accumulator in the power piston. The accumulator could be either of the spring loaded variety or nitrogen gas type. In the event of a loss of pressurized fluid, the accumulator will provide two to three power assisted stops. Upon the first application of the brakes after an engine stall or loss of power steering, you would find approximately 6. If you were to release and apply the brakes again, you would find approximately 3. Once you have depleted all of the stored pressure, the brakes will no longer have power assist and will be manual in their operations. During normal operation, the accumulator is charged by pump pressure though a check valve assembly See Figure 1. The check valve allows fluid into the accumulator, but prevents it from escaping. When the pressure in the power chamber is lost due to a failure, the input rod linkage will override the power piston linkage and cause the check valve to be opened. The open check valve will release the stored fluid in the accumulator into the power chamber which will provide the power assist. Pedal Feel. The hydro boost generates a different pedal feel than a vacuum booster. Basic function can be checked by pumping the brake pedal until hard with the engine off and then starting the engine while maintaining slight pedal pressure. Proper operation should result in the brake pedal sinking down and then pushing back up against your foot. The sinking of the pedal when the engine was started is a result of the power chamber being pressurized. Once the power steering system is at full pressure, it results in the pedal pushing back against your foot pressure. Diagnosis. The hydro boost requires a constant source of pressurized power steering fluid for proper operation. Problems in the power steering system will be reflected in the operation of the hydro boost. Accurate diagnosis of a hydro boost power assist device depends on combining an understanding of their function with a logical diagnostic approach. Hydro boost problems usually break down into the following categories. Noise problems Slow or incomplete pedal return Over sensitive braking and Self applying brakes Note Each of these is covered in the following sections. Noisy Booster. 1.