Expedition 2WD V8-281 4.6L VIN W EFI (1997)
minimum of 30 minutes after the gauge set low pressure gauge indicates 30 in-Hg. This 30 minutes evacuation is necessary to remove any
refrigerant from oil left in the A/C evaporator core. If the refrigerant is not completely removed from the oil, gassing will occur and degrade the
vacuum and appear as a refrigerant leak. After evacuating for 30 minutes, close the gauge set valves and stop the vacuum pump. Observe the low
pressure gauge; it should remain at the 30 in-Hg mark.
NOTE: A vacuum pump, like an automobile, requires maintenance for optimum performance. The condition of the vacuum pump oil is critical to
pump performance and durability. Dirty and/or moisture-laden oil reduces the vacuum pump's ability to draw high vacuum levels that are required
to extract refrigerant from the oil in the A/C evaporator core. As a general rule, vacuum pump manufacturers recommend replacing the oil in the
vacuum pump after every 10 hours of operation. Some manufacturers may recommend even more frequent oil change intervals.
5. If the low pressure gauge reading will not drop to 30 in-Hg when the gauge set valves arc open and the vacuum pump is operating. close the gauge
set valves and observe the low pressure gauge. If the pressure rises rapidly to zero, a large leak is indicated. Recheck the test fitting connections
and gauge set connections before replacing the A/C evaporator.
6. If the low pressure gauge reading rises 10 or more inches of vacuum from the 30 in-Hg mark in ten minutes, a leak is indicated. If a very small
leak is suspected, wait 30 minutes and observe the vacuum gauge. If a small amount of vacuum is lost, operate the vacuum pump with the gauge
valves open for an additional 30 minutes with the heater blower motor on speed 1 to remove any remaining refrigerant from the A/C evaporator
core. Then, recheck for loss of vacuum. If a very small leak is suspected, allow the system to sit overnight with vacuum applied and check for
vacuum loss the next day. Always remember that a leaking fitting, gauge set, or hose connection will appear as a leaking A/C evaporator core.
7. If a vehicle passes the vacuum leak test and is returned within 60 days for loss of cooling due to no refrigerant charge, look elsewhere in the
system for refrigerant leaks, such as the compressor shaft seal or refrigerant line connections.