Vacuum Fill Process
- This procedure is used primarily for vehicles that have hydro-boost brake system and system should be used whenever pump, gear, or hydro-boost is removed, serviced and reinstalled into hydraulic system. To perform this operation, assemble vacuum fill system as shown in illustration. On Saginaw pumps, a modified cap should be constructed as shown. On Ford pumps, the Devac Purging Tool may be used for the filler cap. In place of vacuum pump, intake manifold vacuum source from another vehicle may be used.
- Install system on vehicle and tighten all connections. Close all valves and fill remote reservoir with more fluid than is required to fill system. Open valve no. 1 and allow fluid to drain through filler cap, then close valve. Install cap on filler neck. Open valve no. 2 and 3, start vacuum pump and operate until a gauge reading of 25-30 inches of mercury is obtained. Close valve no. 3 and shut off vacuum pump. If vacuum gauge drops more than 1" in 30 seconds, a leak in system or filler system exists which must be repaired.
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- Restart vacuum pump and open valve no. 3. Operate pump until 25-30" of vacuum is obtained, then close valve no. 2 and shut off vacuum pump. Open valve no. 1 to fill system with fluid. Remote fill reservoir should be higher than steering pump. When fluid stops draining, close valve no. 1 and remove cap from steering pump. Adjust fluid level in pump noting that there will be a slight drop in level when engine is first started and steering cycled. Operate engine at idle for 15 minutes and inspect for leaks. If some air is noted in system, Devac the system.