JLG G12-55A Service Manual - Manual (Page 106)

Engine
7-8 G10-55A, G12-55A
7.4 ENGINE COOLING SYSTEM
7.4.1 Radiator Pressure Cap
John Deere/Perkins: For a 210° F (99° C) system, use a
13 psi (90 kPa) radiator cap. An incorrect or
malfunctioning cap can result in the loss of coolant and a
hot-running engine.
Cummins: For a 210° F (99° C) system, use a 16 psi
(110 kPa) radiator cap. An incorrect or malfunctioning
cap can result in the loss of coolant and a hot-running
engine.
7.4.2 Thermostat Replacement
Before considering thermostat replacement, check the
coolant level, fan belt tension and instrument cluster
temperature indicator.
• If the engine seems to take a long time to warm
up, the thermostat may be stuck in the open
position and requires replacement.
• If the engine runs hot, check the temperature of
the upper radiator hose.
• If the hose is not hot, the thermostat may be
stuck in the closed position.
• If the engine has overheated, performance may
suffer, indicating other damage including a leak-
ing cylinder head gasket, cracked cylinder head
or block, and/or other internal engine damage.
a. Thermostat Removal
1. Park the machine on a firm, level surface, level the
machine, fully retract the boom, lower the boom,
place the travel select lever in the (N) NEUTRAL
position, engage the parking brake, and shut the
engine OFF.
2. Place a Do Not Operate Tag on both the ignition key
switch and steering wheel, stating that the machine
should not be operated.
3. Open the engine cover. Allow the system fluids to
cool.
4. Properly disconnect the battery.
5. Slowly turn the radiator cap to the first stop and allow
any pressure to escape. Remove the radiator cap.
6. Place a funnel at the base of the radiator to channel
the drained coolant into the container. Loosen the
drain plug and slowly remove to allow the coolant to
drain. Transfer the coolant into a properly labeled
container. Dispose of properly if coolant needs to be
replaced. Replace the radiator drain plug.
7. Disconnect the engine water temperature sender (1)
if connected to the thermostat housing.
8. Remove the two capscrews (2) securing the
thermostat housing (3) to the engine.
9. Remove the thermostat housing, old gasket and
thermostat. Clean all gasket surfaces. DO NOT let
any debris into the thermostat opening.
Note: ALWAYS use the correct thermostat and install a
new gasket. NEVER operate the engine without a
thermostat, or engine damage will result.
MY4520
2
1
TYPICAL
THERMOSTAT
2
3