Norwood Parade Auto Spares
54 the Parade, Norwood, Adelaide,
South Australia 5067
Ph 08 83634183 or 8332 8011 open 7 days www.derek.com.au
Home Page www.derek.com.au
The cooling system Story
Automotive engines get hot because of the explosions that take place in the combustion chambers and friction from the moving parts.
The cooling system's job is to keep the engine at ideal operating temperature.
If the engine runs too cool it will operate inefficiently, waste fuel, and wear prematurely. If the engine runs too hot, parts may melt or distort, ruining the engine.
The engine has a water jacket that surrounds the combustion chambers and cylinders that is filled with a 50/50 mixture of antifreeze and water known as coolant.
The coolant absorbs the heat created by the engine, then the water pump pumps it to the radiator to be cooled down.
The thermostat controls the flow of coolant from the engine to the radiator. When the engine is too cool, the thermostat blocks the flow to warm the engine up.
If the engine is too warm the thermostat opens to allow flow to cool the engine down. The radiator is two tanks connected by many thin tubes.
The tubes have thin fins soldered to them that help to dissipate heat. Coolant flows from one tank to the other getting cooler as it travels down the tube.
Cool air blowing across the radiator helps it to remove heat from
the coolant. Normally the movement of the car as you are driving provides
the air flow, but when the car slows down there is a cooling fan to provide
air flow across the radiator. There are two primary types of radiator fans:
mechanical and electric. Mechanical fans are bolted directly to the waterpump
pully or more commonly to a thermostatic fan clutch that lets the fan freewheel
when the coolant temperature is low. Electric radiator fans use an electric
fan motor to spin the fan blades. The motor is controlled by a thermostatic
switch that gives the fan motor power once a preset coolant temperature
is reached, then turns the fan off once the coolant temperature drops below
a preset temperature. The cooling system is pressurized to increase the
boiling point of the coolant. The pressure is regulated by the radiator
cap. When the pressure rises above system's rating (usually about 15 PSI)
the radiator cap releases some of the pressure into the overflow tank. The
overflow tank's level increases as the engine warms up and the coolant expands.
When the engine cools down and the coolant contracts, coolant is sucked
from the overflow tank back into the radiator.
How often should I replace my coolant?
Are long life coolants better?
Q: What is electrolysis?
Should I rod out my radiator or just replace it?
Why does my car overheat only in traffic?
Why does my car overheat only on the freeway?
Why do you use OE (original equipment) thermostats?
When should I replace my hoses?
When should I pull over?
Q: How often should I replace my coolant?
A: We believe coolant should be replaced every 2 years or 30,000 miles regardless of whether the coolant is one of the many "long life" varieties. On some Toyota models Toyota recommends the first service at 45,000 miles and then every 30.000 miles thereafter and on some new Honda models, Honda is recommending the first change at 110,000 miles. You, of course, can make up your own mind, but we strongly urge you go with our recommendation and replace the coolant every every 2 years or 30,000 miles anyway. Coolant serves 3 purposes: it increases the boiling point, decreases the freezing point, and it protects the engine from rust and erosion (electrolysis). All three of these properties are diminished as the coolant ages. Even if you don't drive in especially cold or hot climates it's very important to change the coolant regularly because rust and erosion can damage an engine so badly that it can not be rebuilt.
Q: Are long life coolants better?
A: For some cars we recommend using the Genuine coolant for others
we recommend converting to Prestone after the warranty has expired. There
are currently too many different types of coolant, which is a pain for us.
One coolant for older Hondas, one for newer Hondas, one for older Toyotas,
one for newer Toyota, one for older Mazdas, one for newer Mazdas, and yet
another coolant for Subaru. Taking into account the fact that the old versions
of coolants are all the same, there are still 5 different coolants we have
to stock just to cover the limited makes and models we repair. There are
some advantages to some of the Long Life coolants. The Honda coolant comes
premixed, which is nice. We recommend using the Genuine Honda coolant for
all Hondas 1996 or newer. The Toyota red coolant on the other hand seems
to age just as fast as the old style coolant, is impossible to litmus test
(because of the red dye), and seems to generate a lot of radiator clogging
residue. We recommend removing the Toyota coolant and installing Prestone
as soon as the warranty expires. The Mazda orange coolant is reportedly
different from the Greens and Toyota red, so unless we find out it's safe
to do otherwise, we're going to recommend continuing to use the Genuine
coolant in cars with orange coolant.
Q: What is electrolysis?
A: Electrolysis is the the erosion of metal in the engine caused by
an electrical current generated by the dissimilar metals in the engine when
the coolant PH drops to 7 or below. It's much the like the science experiment
using zinc plate, copper plate, and lemon many of us did in school. Aluminum
in the engine acts as an anode and is transferred to the steel parts of
the engine through the acidic coolant. When aluminum parts like the cylinder
head erode, the cooling passages get wider and often encroach into the head
gasket sealing area. The headgasket will quickly fail if it is not firmly
sandwiched between the head and the block. When a headgasket fails due to
head or block erosion, replacing the failed gasket will not solve the problem,
the eroded part must be replaced, frequently at prohibitive expense. The
cost of replacing the coolant every 30,000 miles over 100,000 miles of driving
is about $150. The cost of replacing and eroded head or block will certainly
be over $2500. It's another case of an ounce of prevention equaling a pound
Q: Should I rod out my radiator or just replace it?
A: Rodding out a radiator is the process of removing the radiator
tanks and pushing rods through the radiator core to clean it. After the
core is clean the tanks are soldered back on. This can be a good repair
but most of the time it makes more sense to just replace the radiator. New
high quality radiators have become so inexpensive that it's getting hard
to recommend repairing an old one. Most of the time the cost of a replacement
radiator is only 30% more than a repair. A new radiator is almost always
available the same day. A new radiator will usually carry a better warranty.
And you should also consider that the metal on your old radiator is going
to be at least somewhat fatigued from years of service and is probably more
likely to develop leaks. If you are planning to keep your car for a long
time it usually makes more sense to buy a new radiator. If you are planning
to keep your car a short time it rodding out the radiator might be a good
Q: Why does my car overheat only in traffic?
A: A car that overheats when it's moving slowly but cools down at
higher speeds usually has a problem with the radiator fan. When the car
is sitting still or moving slowly there is little or no air flow over the
radiator. Without air to cool it, the radiator does a poor job of dissipating
heat. All modern cars have cooling fans to help push or pull air through
the radiator fins at low speeds. When these fans stop working the car can
overheat. You can check to see if your fan is working by letting the car
idle while watching the temperature gauge. You should hear the cooling fan
come on somewhere between 1/2 and 3/4 of the gauge travel. If it has not
come on by 3/4 gauge, then something is wrong with the fan system. You can
drive the car in to the shop instead of towing but avoid stop and go traffic
and watch the gauge carefully.
Q: Why does my car overheat only on the freeway?
A: A car that overheats at high speeds usually has a problem with
its coolant flow. Flow can be reduced by a partially plugged radiator or
a thermostat that does not open all the way (a thermostat that does not
open at all usually causes the car to overheat all the time). If the radiator
is easy to touch it can be checked for cold spots, which would indicate
lack of flow in the area that is cold. On most of the cars we work on you
can't see the radiator, much less touch it. If the radiator can not be checked
for cold spots, we can remove it and send it out to the radiator shop for
flow testing, or we can replace the thermostat and see if it cures the problem.
It's usually cheaper to replace the thermostat than to test the radiator,
so that's what we usually do.
Q: Why do you use OE (original equipment) thermostats?
A: Because they are far superior in quality to any aftermarket brand
that we know of. If you look at a Honda or Toyota thermostat compared to
a Stant the difference is immediately apparent. The OE part has twice the
metal of the aftermarket part. The OE thermostat will be sturdy and obviously
well constructed whereas the aftermarket thermostat will look flimsy. Some
earlier experiences with aftermarket thermostats proved to us that the difference
is more than just their looks. We've had aftermarket thermostat that were
bad right out of the box. With rebuilt engines costing between $2500 and
$6000 it makes a lot of sense to pay an extra $4.00 for a good thermostat.
Q: When should I replace my hoses?
A: Well if you ask Goodyear (a hose manufacturer), they'll say replace
hoses every 3 years or 36,000 miles. If you ask us, that's a waste of money.
When should you replace the hoses? Well, if any of the hoses show signs
of deterioration including cracking when squeezed, oil contamination, swelling,
excessive softness, etc., then the hoses should be replaced. If your car
has made it to 10 years old and the hoses have never been replaced, you
may want to consider replacing the hoses even if they seem OK. We've seen
20 year old original hoses that are still holding pressure. We've also seen
5 - 10 year old hoses, that look OK from the outside, begin to leak from
Q: When should I pull over?
A: When the temperature gauge gets to 3/4 you should start to monitor
it frequently. If the gauge climbs into the red zone or suddenly drops to
below half you should pull over as soon as possible. Engines can be damaged
by driving only a short distance while overheating. After pulling over,
either call a tow truck or wait for a half hour or so and check the coolant
level in the overflow container and the radiator. Squeeze the upper radiator
hose first to see if there is still pressure in the system. You can be badly
burned by opening a radiator cap when a car is overheating, so be patient
and wait for it to cool. If the coolant is low, add water, or coolant if
you have it. Once you've checked or added water start driving towards your
repair shop (Art's we hope). Watch the temperature gauge carefully.
The function of the thermostat is to regulate the flow of antifreeze coming from the radiator to the engine.
Regulating the amount of antifreeze keeps the engine at a constant temperature.
Most fuel injected vehicles require a 195 degree Fahrenheit thermostat to operate efficiently.
If the engine temperature is too cold, the computer will richen the fuel mixture (add more fuel) to compensate,
and if the temperature is too high the engine will overheat and shut down.
A thermostat can fail or stick due to rust or calcium build up in the cooling system.
The cooling system in your car has a lot of plumbing. We'll start at the pump and work our way through the system, and in the next sections we'll talk about each part of the system in more detail.
The pump sends the fluid into the engine block, where it makes its way through passages in the engine around the cylinders. Then it returns through the cylinder head of the engine. The thermostat is located where the fluid leaves the engine. The plumbing around the thermostat sends the fluid back to the pump directly if the thermostat is closed. If it is open, the fluid goes through the radiator first and then back to the pump.
There is also a separate circuit for the heating system. This circuit takes fluid from the cylinder head and passes it through a heater core and then back to the pump.
A - Head Cooling
B - Block Cooling
C - Thermostat
D - Water Pump E - Cooling Fan
F - Radiator Cap
G - Overflow Tank
H - Radiator I - Transmission Cooler
J - Heater Valve
K - Heater Cone
L - Heater Fan
On cars with automatic transmissions, there is normally also a separate circuit for cooling the transmission fluid built into the radiator.
The oil from the transmission is pumped by the transmission through a second heat exchanger inside the radiator.
Cars operate in a wide variety of temperatures, from well below freezing to well over 38 degrees C (100 degrees F). So whatever fluid is used to cool the engine has to have a very low freezing point, a high boiling point, and it has to have the capacity to hold a lot of heat.
Water is one of the most effective fluids for holding heat, but water freezes at too high a temperature to be used in car engines. The fluid that most cars use is a mixture of water and ethylene glycol (C2H6O2), also known as antifreeze.
Pure Water 50 - 50
(C2H6O2) - Water 70 - 30
(C2H6O2) - Water
Freezing Point 0 C (32 F) -37 C (-35 F) -55 C (-67 F)
Boiling Point 100 C (212 F) 106 C (223 F) 113 C (235 F)
By adding ethylene glycol to water, the boiling and freezing points are improved significantly. The temperature of the coolant can sometimes reach 121 to 135 degrees C (250 to 275 degrees F) .
Even with ethylene glycol added, these temperatures would boil the coolant, so something additional must be done to raise its boiling point.
The cooling system uses pressure to further raise the boiling point of the coolant. Just as the boiling temperature of water is higher in a pressure cooker, the boiling temperature of coolant is higher if you pressurize the system. Most cars have a 14 to 15 pounds per square inch (psi) pressure limit, which raises the boiling point another 25 degrees C (45 degrees F), so the coolant can withstand the high temperatures.
Antifreeze also contains additives to resist corrosion.
TRIDON THERMOSTATS ARE UPDATED ON THE WEBSITE BELOW VERY GOOD SITE
THIS PDF TELLS ALL ABOUT THE COOLING SYSTEM AND THE DESCRIPTION OF THE THERMOSTATS
4WD COVERS AH GO GAH HORN AIR FILTERS AIR HORNS ARMREST ASHTRAYS AUTO ACCESSORIES AUTO DRY WASH CLOTHS BABY BOLTS BACK SUPPORTS BADGES BATTERY CHARGERS BATTERY ISOLATOR SWITCH BLIND SPOT MIRRORS BOAT POLISH BOAT WASH BOAT WAX BODY FILLERS BOG BRAKE LIGHT REPAIR KIT BRAKE SHOES BUG SCREENS BULBS BUMPER SPRAY CABLE TIES CAR BATTERIES CAR COVER CAR MATS CAR STANDS CARAVAN COVERS CENTRE CONSOLES CHARGE AND MAINTAIN CHEMICALS CHEMIWELD COMPRESSION TESTER COOLANTS COOLING FANS CUT AND SHAPE MIRROR D SHACKLES DEGREASERS DISC PADS DISC PADS DOOR EDGE PROTECTORS DRI-LUBE DRIVE BELTS DRIVE SHAFTS DRIVING LIGHTS ELECTRIC WATER PUMPS ELECTRICAL TAPE ELECTRONIC IGNITION ENGINE PUMPS EXHAUST CLAMPS FAN BELTS FIBERGLASS FISHING ROD HOLDERS FOOT PUMPS FUEL CANS FUEL FILTERS FUEL HOSE GASKETS GLOSS BLACK GOGGLES H4 LIGHTS H7 LAMPS HAND PUMPS HEATER HOSES HELLA LAMPS HOSE CLAMPS HOUSINGS HYDRAULIC JACKS IGNITION COILS IGNITION LEADS INDUSTRIAL BELTS JACKS JOCKEY WHEELS JUMPER LEADS KEY FOBS L PLATES LEAD REPLACEMENT ADDATIVE LED HEADLAMPS LED LIGHTS LED TORCHES LENS REPAIR KITS LENS TINT LITTER BINS MAG WHEEL CLEANERS MASKING TAPE MASKS MATT BLACK MICRO CHAMOIS MICRO FIBRE CLOTHS MIRRORS MOTHER'S WAX ATTACK POLISHER MOTHERS WAX ATTACK POLISHER MOTOR BIKE STRAPS MUSICAL AIR HORN NAVIGATION LIGHTS NECK SUPPORTS NOLTEC SOFTRIDE URETHANE BUSHES OCCY STRAPS OIL CAPS OIL FILTERS P PLATES PAINT PAINT PETROL CAPS PHILLIPS LAMPS PLASTIC CHAMOIS PLASTIC DYE PLUGS POLISHES POLSHING CLOTHS PROJECTA RACK ENDS RADIATOR CAPS RADIATOR HOSES RECOVERY STRAPS RED BACK SPIDER GEAR KNOBS ROK STRAPS ROOF BARS ROOF BASKETS ROOF RACKS SEAT BELTS SEAT COVERS SLICK50 SLICK 50 SNATCH STRAPS SOLAR PANELS SPANNERS SPARE WHEEL COVERS STAINLESS STEEL BOLTS STEERING WHEEL COVERS SURGE GUARDS SWITCHES SYNTHETIC CHAMOIS SYNTHETIC OILS THERMOSTATS THINNERS TIE ROD ENDS TIMING BELTS TIMING LIGHTS TOOLS TOOLS TOP COAT CLEAR TOW HOOKS TOW ROPES TRAILER CABLE TRAILER LAMPS TRIPLE AIR HORNS TROLLEY JACKS TRUCK HOSES TRUCK WASH TUBE PATCHES TUBELESS TYRE REPAIR KITS TRUCK JUMPER LEADS TWIN AIR HORNS TYRE SPRAY TYRE VALVES UNIVERSAL JOINTS UTE HOOKS VACUMN TESTER WALL PROTECTORS WASHER MOTORS WATER HOSE WATER PUMPS WATERPROOF TRAILER LAMPS WHEEL BRACES WHEEL CHOCKS WHEEL CYLINDERS WINDOW SHADES WINDOW SOX WINDSCREEN WIPERS WIPER ARMS WIPER BLADES WIPER JETS WIPER MOTORS WIPER REFILLS