RayTek AUTOPRO Manual De Instrucciones página 16

Cooling System (Cont.)
yet for some reason the vehicle may be running
hot, have a fluctuating temperature or possibly
overheating. The task is to be able to trouble shoot
and repair the cooling system before the vehicle
overheats and to prevent damage to engine.
Note: Before trouble shooting
cooling system, ensure coolant
leaks DO NOT exist and cooling
fans operate properly.
Radiator Trouble Shooting
Radiators are hard to trouble shoot visually. The
radiator will either leak or not leak. You may be
able to pull the radiator cap off and look inside
at the ends of the passages. The cap may look
new and the seal good. Unless there is excessive
damage or corrosion, the radiator may not be
considered suspect.
Internally there are many passages that can be
blocked or restricted, causing cool spots that
decrease the radiators flow and effectiveness at
lowering the temperature of the coolant to the
engine.
CAUTION: On vehicles with
mechanical fans, use care not to
place tools or hands into mov-
ing blades to prevent injury. On
vehicles with electric fans, be
cautious when working near
because the fan may turn on at
any time.
To trouble shoot for radiator blockage, start engine
and run until normal operating temperature of 85-
105°C (190-220°F) is reached and temperature
stabilizes. For vehicles equipped with electric
cooling fans, ensure fans cycle on and off three
times prior to checking temperatures.
Using the IR thermometer, measure radiator
surface temperature. On vehicles equipped with
a cross flow radiator, measure temperature from
inlet side (hose from thermostat) to outlet side
(hose from water pump inlet). Temperature should

decrease evenly from inlet side to outlet side. On
vehicles equipped with a down flow radiator, mea-
sure temperature from top to bottom. Temperature
should decrease evenly from top to bottom. Also
measure temperature at various points across
radiator fins. If there is a drop in temperature at
one section, this indicates a blockage or restricted
flow. Also check for bent fins restricting airflow.
Thermostat Opening
Temperature
As an engine reaches normal operating tempera-
ture, approximately 85-105°C (190-220°F) on
most vehicles, the thermostat should open and al-
low coolant to flow through the radiator. Using the
IR thermometer, measure the temperature of the
upper radiator hose near the thermostat housing
as engine reaches operating temperature. When
the thermostat opens at the specified temperature,
the temperature of the upper radiator hose should
quickly increase. If temperature at upper radiator
hose near the thermostat housing does not
increase, check for the following:
n Stuck closed thermostat causing coolant not to
flow (engine temperature will be high).
n Stuck open thermostat, causing coolant to flow
constantly and not increase in temperature.
n Air in cooling system (possibly from not being
properly bled).
If temperature remains low and does not reach
normal operating temperature, check for the
following:
n Stuck open thermostat, causing coolant to flow
constantly and not increase in temperature.
n Missing thermostat.
n Thermostat with opening temperature too low
for vehicle.
If temperature of upper radiator hose fluctuates up
and down, check for the following:
n Weak thermostat spring.
n Air in cooling system (possibly from not being
properly bled).
A fluctuating temperature gauge may accompany
fluctuating temperature at upper radiator hose.