The following steps will help when performing this operation:
1. Remove access panel at rear of cabin to gain access to Schrader service valves.
—CAUTION—
Ensure that all system pressure is released before attempting
evacuation. (Refer to Special Servicing Procedures.)
2. Close high and low manifold hand valves. (Refer to figures 21-4 and 21-5.)
3. Connect manifold gauge set to airplane service valves. (Refer to Service Valves.)
4. Connect center manifold hose to inlet of vacuum pump.
—NOTE—
Make sure exhaust port on vacuum pump is open to avoid
damage to vacuum pump.
5. Start vacuum pump and open low side manifold hand valve. Observe compound slight vacuum on low
pressure gauge needle.
6. Continue to operate vacuum pump until 26 to 28 inches of vacuum is observed on low pressure gauge.
Then, extend operation for another 25 minutes.
7. If system cannot maintain 26 to 28 inches of vacuum, close both manifold hand valves and observe
compound gauge.
8. If compound gauge show a loss of vacuum, there is a system leak which must be repaired before
continuing evacuation.
9. If no leaks are evident, reopen both manifold hand valves and continue evacuation for another 30
minutes.
10. Close both manifold hand valves, stop vacuum pump, and disconnect center manifold hose from
vacuum pump.
11. Proceed to charge system in accordance with Charging the System.
—NOTE—
The system should be charged as soon as it has been evacuated.
CHARGING THE SYSTEM
When the system is completely evacuated, use either of the following procedures to charge system.
21 - 52 - 00
Page - 21 - 21
Reissued: August 1, 1986
1G11
PIPER AIRCRAFT
PA-28-236
MAINTENANCE MANUAL
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