From thermostats and water pumps to
plugs, hoses and even the radiator, cooling system troubles can spell a
number of sales opportunities.
With hot summer weather just
around the corner, it’s time to start thinking about selling
replacement cooling system parts. For a cooling system that’s in great
working condition, hot weather poses no challenge. It’s the cooling
systems that are marginal or in need of maintenance or repair that will
run into trouble when the dog days of summer arrive.
most troublesome component in any cooling system is the thermostat.
thermostat’s job is relatively simple: it speeds engine warm-up
following a cold start, and it regulates the engine’s operating
temperature while the engine is running. Accurate temperature control
is critical in today’s engines because emissions control, fuel economy
and performance can all be affected by coolant temperature. The
engine’s powertrain control module (PCM) monitors coolant temperature
via one or more coolant temperature sensors. When the coolant is cold,
the PCM adjusts the fuel mixture, spark timing and other emission
control functions (such as exhaust gas recirculation) accordingly.
Likewise, when the engine reaches its normal operating temperature
(typically 180 to 195 degrees), it readjusts spark timing and fuel
mixture, and allows EGR and other emission functions (such as purging
the EVAP emissions canister) to occur.
Thermostats are fairly
reliable, but may fail after years of service or as a result of engine
overheating. The first sign of trouble is usually a temperature warning
light or a high temperature reading on the temperature gauge. When a
thermostat fails, it usually fails to open. This blocks the flow of
coolant and prevents the cooling system from carrying away the engine’s
waste heat (which is about a third of the heat energy produced by
combustion!). Heat builds up in the engine, and sooner or later the
coolant starts to boil over.
The danger with overheating is that it
can also cause engine damage. Severe overheating, or continuing to
drive while the radiator is boiling over risks damaging the head
gasket(s) and/or scuffing the pistons either of which can be very
expensive to fix.
If an engine is overheating due to a bad
thermostat, the old thermostat should be replaced without delay. It’s a
relatively inexpensive component that usually costs less than $10, and
is fairly easy to replace on most vehicles.
A thermostat also may
jam and fail to close. This can increase the time it takes for a cold
engine to reach normal operating temperature. It also may prevent the
PCM from going into “closed loop” operation where it used input from
the oxygen sensor(s) to adjust the fuel mixture. This can increase fuel
consumption and emissions significantly.
The thermostat is usually
located in a small housing where the upper radiator hose connects to
the engine block. On some cars, though, it may be located where the
lower radiator hose connects to the engine. The most difficult part of
replacing it is draining and refilling the cooling system. Getting all
of the air out of the cooling system can be tricky on many late model
vehicles. Trapped air can prevent the system from being refilled
completely with coolant, which can cause the engine to overheat again.
Some cars have one or more bleeder valves in the cooling system to vent
air when the radiator is being refilled with coolant.
thermostat must have the same temperature rating as the original
thermostat to maintain the proper engine operating temperature.
Remember, the PCM is calibrated for a certain engine temperature, so
changing the temperature can screw things up.
thermostats have a small air vent with a jiggle pin. This type of
design is found on many import applications, and is used to make
refilling the cooling system easier. The jiggle pin valve prevents air
from being trapped under the thermostat.
thermostats also have a special “fail-safe” feature that prevents them
from sticking shut should the unit ever fail. This can provide extra
insurance against overheating.
If a customer’s engine has overheated
because of a coolant leak, and he is buying coolant, hoses, a water
pump or other parts, you should also recommend replacing the
thermostat, too. Why? Because excessive engine temperatures can damage
a thermostat. The little temperature-sensing element that opens the
valve contains wax. If it gets too hot, the wax can be forced out of
its housing. This leaves less wax inside the thermostat to push open
the valve against spring pressure, increasing the chance that it may
not open fully the next time the vehicle is driven.
that may be needed include a new gasket or O-ring for the thermostat
housing, and possibly a new housing if the old one is badly corroded.
WATER PUMP WOES
next most troublesome component in the cooling system is the water
pump. Most original equipment water pumps should last upward of 100,000
miles, but they won’t last forever and some may start to leak or make
noise long before the odometer hits six figures. Most OEM water pumps
have a hard ceramic seal that prevents coolant from leaking out around
the pump shaft. Over time, the seal can wear and start to leak. Coolant
neglect and the formation of sediment in the coolant due to corrosion
can accelerate seal wear and cause premature pump failure.
bearing that supports the pump shaft and impeller can also wear as the
miles add up. Any wobble that occurs in the shaft will also accelerate
seal wear and lead to leaks.
Cooling system sealer products that
work great for plugging small radiator and even head gasket leaks
cannot seal a leaky water pump. The only fix is to replace the pump if
it is leaking coolant.
Another problem that can affect some water
pumps is impeller wear. Some late model water pumps have plastic
impellers instead of stamped steel impellers. Plastic is lighter and
allows a more refined impeller design to reduce drag and improve
pumping efficiency. But plastic also is a soft material that can be
easily eroded by sediment in the coolant. It also is vulnerable to
cavitation erosion. This occurs when the rotating pump forms small
bubbles in the coolant. When the bubbles pop, they create shock waves
that slowly chip away at the plastic impeller. Over time, the impeller
blades can wear down to almost nothing which causes the engine to run
hot and overheat because the pump is not circulating much coolant.
Impellers are not available separately as a repair item, so the pump
must be replaced as an assembly.
Related items that may be needed
when replacing a water pump include a new V-belt or serpentine belt if
the old belt is cracked, glazed or making noise. Your customer also may
need thread sealer for water pump bolts that thread into open holes
that extend into the engine’s cooling jacket.
If the application is
rear-wheel drive vehicle with a mechanical cooling fan, your customer
may also need a new fan clutch. The silicone fluid inside a fan clutch
that allows it to slip suffers sheer breakdown over time. This slows
the speed of the fan, which may lead to engine overheating when moving
in slow traffic with the A/C on during hot weather. Any wobble in the
fan clutch, or any sign of fluid leakage, or excessive slippage would
call for a new fan clutch.
Hoses are another cooling
system component that often have to be replaced. The synthetic rubbers
that are used in late model radiator and heater hoses are much longer
lived than the natural rubbers and synthetic rubbers which where
commonly used a couple of decades ago. Most late model OEM hoses are
capable of lasting 10 years or more, and 100,000-plus miles. Even so,
older vehicles and high-mileage vehicles may need new hoses to replace
old ones that have become hard, or are cracked or are leaking.
hoses are used on most late model vehicles, so some trimming may be
required to make a replacement hose fit correctly. The old clamps also
should be replaced with new ones as old clamps may be weak or corroded.
one hose has failed, and a customer is buying a replacement, you should
warn him that the other hoses on his vehicle also may be on the verge
of failure. Replacing all of the hoses now can prevent a breakdown
later. This includes the upper and lower radiator hoses, and the heater
Also called freeze plugs, these little
plugs seal the casting holes in the engine block. They are usually
stamped steel and pressed into place. Over time, the plugs may corrode
from the inside out, especially if the coolant has never been changed
which is common problem with today’s long life coolants (they last five
years, but not forever). If a plug is leaking, it needs to be pried out
and replaced with a new one. Some replacement plugs have a rubber
expansion grommet that makes installation easier. A related item that
will be needed with a press fit plug is sealer.
RADIATOR & HEATER CORE
and heater cores are usually trouble-free, but on some vehicles (many
Chrysler cars) repeat heater core failures have been blamed on
electrolysis corrosion. The problem may be due to coolant neglect or
improper grounding of the heater core to the chassis.
late model vehicles have aluminum radiators. With proper cooling system
maintenance, the radiator should last the life of the vehicle. But
radiators can fail as a result of internal corrosion (coolant neglect),
vibration damage that causes cracks and leaks or physical damage
(frontal collision or stone damage). On radiators that have plastic end
tanks, the seal between the radiator core and end tank may develop a
leak. The plastic tank also can be damaged by internal erosion caused
by sediment in the coolant, or by extreme overheating.
radiators can be tricky to fix, though small leaks may be successfully
sealed with cooling system sealer or externally applied
high-temperature epoxy. A radiator with multiple leaks, physical damage
or leaky end tanks usually has to be replaced.
The main points to
keep in mind about selling a replacement radiator is that it must have
the same width, height and thickness as the original radiator to fit
properly. Also, it must have the same hose connection locations and
fittings. Many radiators have an internal loop of pipe that serves as a
cooler for the automatic transmission fluid. So if the vehicle has an
automatic transmission with a radiator ATF cooler, the replacement
radiator must also have one.
Also recommended is a new radiator cap
(unless the cap is on the coolant reservoir tank). Many radiator caps
are spring-loaded to maintain a certain pressure in the cooling system.
Over time, the spring may weaken causing a loss of pressure. This can
lead to coolant loss and overheating. A bad seal on the underside of
the cap can cause the same kind of problems. A replacement cap should
have the same pressure rating as the original.
cooling system parts almost always requires draining and refilling the
cooling system. Today’s long-life coolants are supposed to be good for
five years or 150,000 miles. Unfortunately, many people think that
means forever. It doesn’t. After five or more years of service, the
corrosion inhibitors are usually worn out and the coolant needs to be
replaced. If the coolant is not replaced for preventive maintenance,
corrosion can start to eat away at the inside of the cooling system,
attacking the radiator, heater core, water pump, engine, even rubber
Any customer who is buying cooling system parts, therefore,
should also be encouraged to buy some fresh antifreeze. Premixed
coolant is easier to install and reduces the risk of coolant
contamination by dissolved minerals or salt in tap water.
owner should use the same type of coolant that was the factory-fill in
his cooling system. It doesn’t have to be the same brand, but it should
be a long-life organic acid technology (OAT) type of coolant that meets
the OEM requirements or is a “universal” (all makes/all models) type of
product. The less expensive and shorter-lived “green” coolant, which is
okay for older cars, should not be used in late model cooling systems
that specify a long-life or hybrid coolant.
cooling system related parts that may be needed include a new automatic
tensioner for a serpentine belt if the old tensioner is not maintaining
proper tension or is making noise.
A coolant sensor may have to be
replaced if it is defective, not reading accurately or is leaking. A
bad coolant sensor can prevent the PCM from going into closed loop,
upsetting the engine’s fuel and emissions calibrations. A quick way to
check a coolant sensor is to use a scan tool to compare the coolant
temperature reading against the ambient air temperature sensor reading
when the engine is cold. Both should show the same temperature. If not,
one of the sensors is off.
A bad fan relay or a burned out fan motor
can prevent the radiator fan from coming on when extra cooling is
needed. On most vehicles, the fan(s) should come on when the A/C is
turned on. If the fan circuit is not working, the engine may overheat
when the A/C is on, or when the vehicle is creeping slowly in traffic.
The relay for the fan circuit is usually located in the engine
compartment, and is relatively inexpensive and simple to replace once
you find it.