Chrysler PT Cruiser, Руководство по обслуживанию и ремонту, Страница: 283 / 2078

OPERATION
The pressure cap allows the cooling system to oper-
ate at higher than atmospheric pressure. The higher
pressure raises the coolant boiling point, allowing
increased radiator cooling capacity. The pressure cap
will release cooling system pressure in a range of
97–124 kPa (14–18 psi).
A vent valve located in the center of the cap allows
a coolant flow to and from the coolant recovery sys-
tem bottle. This valve is spring loaded in the closed
position. However, it must be free to open during sys-
tem cool-down. If the valve is stuck shut, the
radiator
hoses will collapse on cool-down.
Clean the vent valve (Fig. 15) to ensure proper
sealing function.
A gasket in the pressure cap seals the top of the
filler neck so that vacuum is maintained to draw
coolant back into the system from the coolant recov-
ery system bottle.
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - COOLING SYSTEM
PRESSURE CAP TESTING
Dip the pressure cap in water. Clean any deposits
off the vent valve or its seat and apply cap to end of
the Pressure Cap Test Adaptor that is included with
the Cooling System Tester 7700 (Fig. 16). Working
the plunger, bring the pressure to 104 kPa (15 psi) on
the gauge. If the pressure cap fails to hold pressure
of at least 97 kPa (14 psi), replace the pressure cap.
CAUTION: The Cooling System Tester Tool is very
sensitive to small air leaks that will not cause cool-
ing system problems. A pressure cap that does not
have a history of coolant loss should not be
replaced just because it leaks slowly when tested
with this tool. Add water to the tool. Turn tool
upside down and recheck pressure cap to confirm
that cap is bad.
If the pressure cap tests properly while positioned
on Cooling System Tester (Fig. 16), but will not hold
pressure or vacuum when positioned on the filler
neck. Inspect the filler neck and cap top gasket for
irregularities that may prevent the cap from sealing
properly.
DIAGNOSIS AND TESTING - COOLING SYSTEM
PRESSURE RELIEF TESTING
WARNING: THE WARNING WORDS “DO NOT OPEN
HOT” ON THE PRESSURE CAP IS A SAFETY PRE-
CAUTION. WHEN HOT, THE COOLING SYSTEM
BUILDS UP PRESSURE. TO PREVENT SCALDING
OR OTHER INJURY, THE PRESSURE CAP SHOULD
NOT BE REMOVED WHILE THE SYSTEM IS HOT
AND/OR UNDER PRESSURE.
The pressure cap upper gasket to filler neck seal
can be checked by removing the overflow hose at the
filler neck overflow nipple (Fig. 17). Attach the radi-
ator pressure tester to the filler neck overflow
nipple, and pump air into the system. The pressure
cap upper gasket should relieve pressure at 69-124
kPa (10-18 psi), and hold pressure at 55 kPa (8 psi)
minimum.
There is no need to remove the pressure cap at any
time except for the following purposes:
•
Check and adjust coolant freeze point
•
Refill system with new coolant
•
Conducting service procedures
•
Checking for leaks
Fig. 16 Testing Cooling System Pressure Cap
1 - PRESSURE CAP
2 - PRESSURE TESTER
Fig. 17 Cooling System Pressure Cap to Filler Neck
1 - OVERFLOW NIPPLE
2 - MAIN SPRING
3 - GASKET RETAINER
4 - STAINLESS-STEEL SWIVEL TOP
5 - RUBBER SEALS
6 - VENT VALVE
7 - THERMOSTAT HOUSING/ENGINE OUTLET CONNECTOR
8 - FILLER NECK
PT
ENGINE - 2.0/2.4L DOHC 7 - 47
COOLING SYSTEM PRESSURE CAP (Continued)