The spool valve vents the power chamber to the return line of the power steering pump reservoir. 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. When the brakes are unapplied the spool valve is positioned as shown in Figure 8. The spool valve’s position is determined by the lever assembly which is connected to the input rod.
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 valve fits into a precisely machined bore that is part of the hydro-boost housing as shown in Figure 7. The housing is fitted with three ports as identified in Figure 6. These include the housing, power chamber, input rod assembly, a lever assembly, a power piston, spool valve assembly and an output rod. The spool valve in a hydro-boost works in a similar fashion.įigure 5 shows a cutaway of a hydro-boost with all the major components labeled. The fluid flow is now from port 1 to port 3 with port 2 being blocked by land #2. Figure 4 shows the spool valve moved to the left which changes the fluid flow. 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. The path of the pressurized fluid from port 1 is determined by the position of the spool valve. The raised portions of the cylinder are called lands while the indentations are called annular grooves.įigure 3 shows a simplified spool valve positioned in a bore with three ports. The surface of the spool valve is highly polished to form a sealing surface. A spool valve is basically a hollow cylinder with a number of rings machined into it (see Figure 2). Spool valves are used in a variety of hydraulic components, such as the valve body of an automatic transmission. The power steering pump supplies pressurized fluid for both the power steering gear and hydro-boost.įluid flow in and out of the hydro-boost is controlled by what is known as a spool valve. The hydro-boost is plumbed in line with the steering gear. A typical hydro-boost is shown in Figure 1. Proper diagnosis of hydro-boost related problems requires an understanding of how the system works.
#2001 gmc safari parts series#
* Ford Super Duty series trucks equipped with Diesel and * Dodge Ram equipped with Cummins turbo diesel * 1996 and newer Cobras and all V8 Mustang Hydro-boost has been used on a variety of vehicles since its introduction and OEM applications presently include:
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