The engines cooling system is designed to keep the engine from overheating while in
operation. When this system fails due to a leak or an engine mechanical or
cooling system failure it will enable the engine to overheat which will produce internal damage and
cause the engine to stop running. There are several
over heating symptoms that will let you know if the engine is having a
problem such as the temperature warning light coming on and noticing the temperature gauge
is in the red or close to it. This condition may also be accompanied by a
burning coolant smell or reduced engine power. In any case if you think your
car's engine is overheating you should safety pull to the side of the road and
shut the engine off to avoid internal engine damage.
What Goes Wrong?
Your car's engine produces heat due to the
combustion process. The cooling system is used to maintain operational
temperatures which have a number of components that can fail or leak coolant due to
the constant heat and vibration of the engine. When internal temperatures go
beyond their designed capabilities internal damage can occur such as a cracked cylinder
head or engine block. One of the most common major failures is a blown head gasket
which is used to seal the cylinder head to the engine block and allow coolant to
enter either the combustion chamber or the engine oiling system. Further damage
can include seized pitons and collapsed piston rings, both will cause low
compression and can contribute to the
engine not starting after an overheating event.
Let's Get Started!
Always use caution when checking out an engine overheating problem because
the cooling system has up to 18 pounds of pressure and is filled with
hot coolant which can cause burns. Always allow the engine to cool before
testing or inspection.
1. Low Coolant
The cooling system must maintain pressure
and a proper coolant level or the engine will overheat. Wait until the engine as
cooled off and locate and slowly remove the coolant reservoir or radiator cap
and check the coolant level. A small amount of pressure
should be released which is normal if the radiator cap is good. Over time the
coolant level can be a little low which is normal. If the system is continuously low or almost
completely out the
system or engine has coolant leak which needs to be fixed to keep the engine
from overheating. If the system is absent of pressure (you can tell this by
squeezing the upper radiator hose and feel pressure) and the system
seems to be full of coolant then the radiator or coolant reservoir cap needs to
Watch the Video!
Some car designs hold pressure in their coolant reservoir. In these cases the
cap will unscrew from the container.
2. Bad Cooling Fan
Cooling fans can be either mechanical which are belt driven by the engine, or
electric mounted on the radiator.
are located directly behind the radiator and are used to move
air through the radiator core which helps remove heat from the coolant at low speeds. If this
fan stops operating the engine will overheat or run hot. To check an electric motor cooling fan,
remove the key from the ignition switch and away from the car. Then reach in and
spin the fan blade by hand, it should "freewheel" and spin easily. If it sounds
rough or is difficult to turn it has gone bad and needs replacement. There is an
easy way to check the electrical portion of the cooling fan system if the
has air conditioning. Start the engine and turn the air conditioner
to the coldest setting. Within one minute of the car air conditioner operating
the cooling fan(s) should activate. If the fan does not come on first
fuse and then the
relay. If both of these items check out then the
fan motor has most likely burned out and needs replacement.
Watch The Video!
If your car is not designed with an electric fan it will have a
clutch which is attached to the water pump and driven by the engine. This device
engages and disengages the fan blade via a temperature sensor at the center of
the clutch. When a
fan clutch goes bad it fails to "lock up" which diminishes
the fan blade performance causing the engine to overheat by allowing the blade to freewheel
and not pull air through the radiator. When the engine is hot this clutch should
engage which is followed by a roaring sound as the fan starts to work. If the engine is hot and you can see the blade freewheeling
while the engine is running
the clutch fan has gone bad and needs replacement.
Watch the Video!
3. Stuck Thermostat
engine thermostat will not allow the coolant to flow into the
radiator when the engine is cold. When the thermostat goes bad it can do so by sticking closed. This means the
coolant never gets a chance to be circulated to the radiator. When this
failure occurs the engine will overheat rapidly usually within the first fifteen
minutes of driving and can be accompanied by a thumping sound as the hot coolant
is trying to mix with the cold coolant in the radiator. Do not open the radiator
to check the coolant level. Allow the
engine to cool
before replacing the thermostat.
Watch the Video!
4. Plugged Radiator
is responsible for dropping the temperature of the engine coolant and can fail
in a three different ways the first is external blockage. Because your
car hugs the road it is constantly being bombarded with debris such as dirt,
hair, leaves, trash and bugs to name a few. Because of this cooling fins can
become plugged stopping air flow through the radiator core causing the engine to overheat. This
condition can be hard to detect because the air conditioner condenser sits in
front of the radiator in some cases. Use a flashlight to help check for blockage
and then use a garden hose to pressure wash the radiator from the backside (facing forward) to
help clean and unplug the radiator.
The second way a radiator can fail is to become plugged internally. To check
for this condition, remove the radiator cap when the engine is cold look inside
using a flashlight. You may need to drain some of the coolant out to see the
ends of the radiator core tubes. In the example below the tubes appear clear
with no corrosion around the end which is what you want.
When a radiator plugs internally these tubes become clogged due to lack of
flush) calcium will then stop the coolant flow which inhibits the radiator's cooling ability. This condition generally occurs
gradually over time and will be more noticeable when climbing a grade or in warmer
weather. The third way a radiator can fail is to leak. This will cause the
system to lose coolant and cause overheating. In either case the
radiator must be replaced.
Watch the Video!
5. Bad Water Pump
The water or coolant pump is a mechanical pump which is responsible for circulating
coolant throughout the radiator and into the engine which is driven by the
engine serpentine, timing belt or timing chain. On most hybrid engines this pump is powered by an electric motor.
When a water pump fails it can
do so in one of two ways. First, it can cause a leak which is what happens when
its shaft seal fails or when the shaft bearings fail destroying the seal. This
can sometimes be accompanied by squeaking, squealing, grinding or a rattling
sound. In some instances the impeller of the pump will become dislodged stopping
the pumping action. In either case the
water is pump
bad and replacement is required.
Watch the Video!
6. Blown Head Gasket
A head gasket is used to seal the combustion process within the engine block
and cylinder head. This gasket is prone to failure due to natural engine block and cylinder head
expansion and contraction as the engine heats up and then cools down. Corrosion
due to lack of cooling system maintenance can also play a factor in the gasket's
failure. If the block is cast iron and the cylinder head is made of aluminum a process called
electrolysis can take place caused by dissimilar metals. This can cause coolant to enter the engine's
oiling system and exhaust gasses to be forced into the cooling system which displaces the coolant from the system.
This problem is becoming more popular as engine components such as engine blocks
and cylinders heads become more lightweight. Fortunately to
test for a blown head gasket is a simple process. When this gasket fails
it can also cause a
rough running engine at start up.
Watch the Video!
7. Leaking Transmission Cooler
Most automatic transmission vehicles utilize a fluid cooler inside the radiator to
help remove heat from the transmission fluid. When this cooler fails it will
allow transmission fluid to contaminate the coolant inside of the cooling system which
inhibits the heat transfer of the coolant. This problem is easy to check for by simply opening
the radiator or reservoir cap when the engine is cold and look for a pink milky
substance. If found the system will need to be drained and flushed along with a
new radiator installed. As a side note if this condition exists the
fluid may need to be flushed and changed as well. This is because the
radiator maintains its pressure for a short time when the engine is shut off.
Also when the engine is shut off, the transmission fluid pressure dropping to zero immediately which allows coolant to be pushed into the transmission
fluid lines and into the transmission.
8. Leaking Engine Oil cooler
Some engines are designed with engine oil coolers to reduce heat by way of the engine oil. This is achieved by running
radiator coolant through the cooling fins of the oil cooler to reduce heat. When
this cooler fails it can cause engine oil to be released into the cooling system
in much the same way as when a transmission cooler fails. This can be checked in
the same fashion as the transmission cooler failure but instead of pink milky goo it will be tan or brown in the
reservoir or radiator. If found the engine oil and radiator coolant should be changed along with
the engine oil cooler.
9. Plugged Catalytic Converter
As a catalytic converter starts to fail it can partially plug up which causes
the engine to have less power. To compensate for this low power the driver will
increase the throttle which creates excessive heat inside the engine while overloading the cooling system.
This condition is always be accompanied by
low engine power. To
test the cat converter use an infrared temperature tester to monitor the
ingoing and outgoing temperatures.
Watch the Video!
Got Any Questions?
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