Husqvarna 2011 TE 630 Workshop Manual page 406

Coolant level check
Coolant takes the heat from the piston-cylinder-and-head assembly and transfers
it to the radiator, where it is released to the atmosphere. Checking coolant level at
regular periods is critical to ensuring proper operation of the cooling system.
Without cooling medium (water), no heat exchange occurs between
cylinder head and radiator. The cylinder and piston assembly will
overheat and seize and in the worst scenario, crankshaft damage
may result.
If the event of engine overheating, check that the radiator is full.
Level in the radiator must be checked from cold (see Section D).
In the event you need to check level when the engine is hot, be sure to discharge
pressure gradually.
The radiator cap (1) has a pressure-relief position to depressurize the system
safely.
Failure to follow the above instructions will create a risk of scalding
for operator and any persons standing nearby.
Because the cooling fan (2) can be activated even when the start
switch is in OFF position, always keep at a safe distance from the
fan blades.
A. Coolant level
B. Breather hose
Part. N. 8000 H2051 (02-2010)
ENGINE COOLING
N.3