Mityvac 06820 Diesel Compression Test Adapters - Manual (Page 17)

Page Number - 17
Form 822378
3) If full vacuum flows through the valve
when heated, it is okay. If there is no
vacuum flow or there is vacuum flow
when the coolant is cold, replace the
valve.
Follow this procedure to test the three-
port vacuum-switching valve:
1) Apply 10” Hg of vacuum with your
vacuum pump to the middle port of the
valve with a vacuum gauge at each
of the other two ports.
2) Refer to the same color-coded valves
and same temperature specifications
as for the two-port valve above. If the
vacuum switches at the specified
temperature, the valve is okay. If there
is no vacuum to the lower port above
the specified temperature, replace the
valve.
The four-port valve must be tested two
times, once at the top two ports and once
at the bottom two ports as shown in the
accompanying illustration (FIGURE 14).
1) Apply 10” Hg of vacuum with your
vacuum pump to one of the top two
ports. The valve should hold vacuum
when above the specified operating
temperature.
2) If flow occurs when the valve is
warm, replace it.
3) For the lower two ports, vacuum must
pass through the valve only when the
engine is warm; otherwise, replace the
valve.
BRAKE BLEEDING
Many brake systems today feature Anti-
Lock functions and electronic controls.
Many of these systems use a high pres-
sure electric pump to keep the system
pressurized. When bleeding or servicing,
these systems require special proce-
dures and cautions.
Always observe the following precau-
tions when servicing Anti-Lock brake
system:
•
ALWAYS wear safety goggles when
servicing high pressure brake
systems.
• ALWAYS depressurize the ABS
system prior to adding fluid or
attempting service or repair.
• Unless instructed to by the manufac-
turer’s procedure, NEVER open a
bleeder valve or loosen a hydraulic
line while the ABS system is pressur-
ized.
• ONLY use recommended brake fluids.
DO NOT use silicone brake fluid in
ABS equipped vehicles.
• Always refer to an appropriate repair
manual for additional information an
Anti-Lock brake systems.
DEPRESSURIZING ANTI-
LOCK BRAKE
SYSTEMS
Always refer to the vehicle owner’s
manual or appropriate service manual for
additional information on depressurizing
procedure. The procedure will work on
most Anti-Lock brake systems. Ensure
ignition switch is in the OFF position or
disconnect the negative battery cable.