Intake Manifold - Six-Cylinder Engine; Hoses; Thermostat; Thermostat Replacement - Jeep J-10 Series 1982 Technical & Service Manual

Inspecting for Inlet Restrictions
With six- and eight-cylinder engines, poorheater per
formance may be caused by a casting restriction in the
water pump heater hose inlet.
NOTE: This procedure does not apply to thefour-cylin
der engine.
(1) Drain sufficient coolant from radiator to permit
removal of heater hose from water pump.
(2) Remove heater hose.
(3) Check inlet for casting flash or other
restrictions.
NOTE: Remove pump from engine before removing re
striction to prevent contamination of coolant with
debris. Refer to WaterPump Removal
INTAKE MANIFOLD-SIX-CYLINDER ENGINE
Coolant Row Test
If restricted coolant flow is suspected, perform the
following test procedure.
NOTE: DO NOT WASTE reusable coolant. If solution
is clean and being drained only to service the cooling
system, drain into a clean containerfor reuse.
WARNING: DO NOT loosen radiator draincock with
system hot and under pressure because serious burns
from coolant can occur.
(1) Drain coolant from radiator to level below in
take manifold and remove coolant hoses from front and
rear fittings on intake manifold.
(2) Install 12-inch (305 mm) length of 5/8-inch (16
mm) inside diameter (ID) heater hose on intake mani
fold front fitting and place funnel in hose. Funnel must
have minimum outlet size of 3/8-inch (9.5 mm) inside
diameter (ID).
(3) Fill clean container with 1/2 gallon (1.9 liter) of
water.
(4) Begin pouring water into funnel and, with time
device in view, time water flow through manifold when
water starts flowing down funnel.
(5) Continue pouring water into funnel until con
tainer is empty and continue timing water flow until
funnel is empty.
(6) If water flows through intake manifold coolant
passage in 25 seconds or less, flow interval is correct and
passage is not restricted.
(7) If water takes longer than 25 seconds to flow
through intake manifold, inspect manifold coolant inlet
and outlet for casting flash or other restrictions, correct
as necessary and proceed to next step.
(8) Check length of each hose fltting extending into
intake manifold coolant passages. Extension must not
COOLING SYSTEMS 1C-9
be so excessive in length that coolant flow is restricted.
Replace fitting(s) if length is excessive.
(9) If intake manifold coolant passages are re
stricted and cannot be cleared, replace intake manifold.
Refer to replacement procedure in Chapter IB.
HOSES
Rubber hoses route coolant to and from the radiator
core and heater core. A heater coolant control valve is
installed in the heater core inlet hose to control coolant
flow to the heater core.
The lower radiator hose on all engines is reinforced
with a wire coil (stiffener) to prevent collapsecaused by
water pump suction.
Hose Inspection
Inspect hoses at regular intervals. Replace hoses that
are cracked, feel brittle when squeezed or swell exces
sively when under pressure.
In areas where specific routing clamps are not pro
vided, ensure hoses are positioned to clear exhaust
manifold and pipe, fan blades and drive belts. Other
wise, improperly positioned hoses will be damaged, re
sulting in coolant loss and engine overheating.
The lower radiator hose on all engines is fitted with an
internal wire coil (stiffener) to prevent hose collapse.
When performing a hose inspection, check for proper
position of the wire coil.
THERMOSTAT
A pellet-type thermostat controls the operating tem
perature of the engine by controlling the amount of
coolant flow to the radiator. On all engines, the thermo
stat is closed below 195°F (90°C). Above this temper
ature, coolant is allowed to flow to the radiator. This
provides quick engine warmup and overall temperature
control. An arrow or the words TO RAD is stamped on
the thermostat to indicate the proper installed position.
The same thermostat is used for winter and summer
seasons. An engine should not be operated without a
thermostat, except for servicing or testing. Operating
without a thermostat causes longer engine warmup
time, unreliable warmup performance and crankcase
condensation that can result in sludge formation.
Thermostat Replacement
NOTE: DO NOT WASTE reusable coolant If solution
is clean and is being drained only to service the cooling
system, drain coolant into a clean containerfor reuse.
WARNING: DO NOT loosen radiator draincock with
system hot and under pressure because serious burns
from coolant can occur.