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CYLINDER HEAD (Continued)
DIAGNOSIS AND TESTING—CYLINDER HEAD
GASKET
A cylinder head gasket leak can be located between
adjacent cylinders or between a cylinder and the
adjacent water jacket.
Possible indications of the cylinder head gasket
leaking between adjacent cylinders are:
• Loss of engine power
• Engine misfiring
• Poor fuel economy
Possible indications of the cylinder head gasket
leaking between a cylinder and an adjacent water
jacket are:
• Engine overheating
• Loss of coolant
• Excessive steam (white smoke) emitting from
exhaust
• Coolant foaming
CYLINDER-TO-CYLINDER LEAKAGE TEST
To determine if an engine cylinder head gasket is
leaking between adjacent cylinders, follow the proce-
dures in Cylinder Compression Pressure Test (Refer
to 9 - ENGINE - DIAGNOSIS AND TESTING). An
engine cylinder head gasket leaking between adja-
cent cylinders will result in approximately a 50–70%
reduction in compression pressure.
CYLINDER-TO-WATER JACKET LEAKAGE TEST
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING WITH COOLANT PRES-
SURE CAP REMOVED.
VISUAL TEST METHOD
With the engine cool, remove the coolant pressure
cap. Start the engine and allow it to warm up until
thermostat opens.
If a large combustion/compression pressure leak
exists, bubbles will be visible in the coolant.
COOLING SYSTEM TESTER METHOD
WARNING: WITH COOLING SYSTEM TESTER IN
PLACE, PRESSURE WILL BUILD UP FAST. EXCES-
SIVE PRESSURE BUILT UP, BY CONTINUOUS
ENGINE OPERATION, MUST BE RELEASED TO A
SAFE PRESSURE POINT. NEVER PERMIT PRES-
SURE TO EXCEED 138 kPa (20 psi).
Install Cooling System Tester 7700 or equivalent to
pressure cap neck. Start the engine and observe the
tester's pressure gauge. If gauge pulsates with every
power stroke of a cylinder a combustion pressure
leak is evident.
ENGINE 2.7L DOHC
CHEMICAL TEST METHOD
Combustion leaks into the cooling system can also
be checked by using Bloc-Chek Kit C-3685-A or
equivalent. Perform test following the procedures
supplied with the tool kit.
STANDARD PROCEDURE - Cylinder Head Oil
Gallery Cup Plug Service
NOTE: DETERMINE WHICH CUP PLUG IS LEAKING
BEFORE PERFORMING THIS PROCEDURE. IF NEC-
ESSARY, PERFORM AN ENGINE OIL LEAK DYE
TEST.
Each cylinder head on a 2.7L engine has 6 external
oil gallery cup plugs. It is not necessary to remove
the original cup plug to install a new cup plug. The
cup plug bore is deep enough to allow for two plugs.
If it becomes necessary to service an oil gallery cup
plug, perform the Repair Procedure.
NOTE: INSPECT THE CUP PLUG BORE IN QUES-
TION FOR THE PRESENCE OF TWO CUP PLUGS. IF
THE CUP PLUG FLANGE IS JUST INSIDE (1–2 MM)
THE CHAMFERED EDGE OF THE BORE TWO CUP
PLUGS ARE ALREADY IN PLACE AND THE CYLIN-
DER HEAD CANNOT BE REPAIRED.
Repair Procedure
(1) Remove component(s) necessary to gain access
to the oil gallery cup plug requiring service.
NOTE: SOME OF THE OIL GALLERY CUP PLUGS
ARE SERVICEABLE WITH THE HEAD INSTALLED
ON THE ENGINE AND THE ENGINE IN THE VEHI-
CLE, WHILE OTHERS REQUIRE REMOVING THE
AFFECTED CYLINDER HEAD FROM THE ENGINE.
IN EITHER CASE ONLY REPLACE THE CUP PLUG
REQUIRING SERVICE.
(2) Clean the cup plug bore with brake cleaner and
compressed air. It is not necessary to remove the
existing cup plug.
(3) Lightly coat the new cup plug with sealer; p/n
04318083.
(4) Using an appropriate installation tool drive the
new cup plug into the bore until the flanged edge of
the plug is just inside (1-2 mm) the chamfered edge
of the bore (Fig. 16).
(5) Allow the sealant to cure for at least 20 min-
utes.
(6) Assemble any components removed in step # 1
as necessary.
9 - 167
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