Piper Arrow IV Turbo Maintenance Manual page 468

DISTRIBUTION .
VACUUM SYSTEM SERVICE TIPS.
The following information is intended to acquaint field service personnel with a means to diagnose
vacuum system service symptoms on those components which are serviced by removal and replacement.
These items include hoses, clamps, gyro filters, vacuum regulating valves and vacuum gauges.
1. Hoses and Clamps:
A. These items should be examined periodically and inspected carefully whenever engine
maintenance activities cause hose disconnections to be made at the pump, regulating valve, gyros
and/or vacuum gauge.
B. The ends of the hoses should be examined for rubber separation and slivers of rubber on the inside
diameter of the hoses. These slivers can and do become detached. If this happens, the vacuum
pump suck these loose particles and eventually ingest them. This can cause premature pump
service.
C. Hose clamps and fittings should be replaced when broken, damaged or corroded.
When replacing any of the threaded fittings, DO NOT USE PIPE
DOPE or any other anti-seize tape or compound. The
AIRBORNE fittings are all cadmium plated to avoid the need for
any other anti-seize materials. The reason for this caution is to
protect the pump from ingesting any foreign materials that could
cause premature service.
2. Vacuum Gauges:
A. Vacuum gauges seldom require service and usually are replaced when malfunctions occur.
Vacuum gauge failure in a properly operating vacuum system
does not impair safety of flight.
B. If the vacuum gauge malfunctions in a manner to cause an incorrect reading in normal cruise
conditions, the gauge must be checked by comparing the reading with a gauge of known accuracy.
If the gauge is indicating correct values and the system vacuum level is not in accordance with the
specified vacuum, then and only then should the regulator be reset.
C. Visual examination of the gauge performance should cover the following steps:
(1) With engine stopped and no vacuum applied to the gauge, its pointer should rest against the
internal stop in the 9 o'clock position. Any other displacement from this position suggests
need for replacement.
(2) A slight overshoot during engine startup, not to exceed half an inch (1/2") of mercury, is
normal and is not cause to replace gauge.
(3) With engine operating at normal cruise RPM, the gauge should read from 4.9 inches to 5.1
inches of mercury (vacuum).
(4) At 1200 RPM, the vacuum gauge reading should be more than four inches of mercury.
PIPER AIRCRAFT
PA-28RT-201 / 201T
MAINTENANCE MANUAL
—CAUTION—
—NOTE—
2H21
37-10-01
Page 37-03
December 1, 1978