Modifying the cooling system won't really improve
gas mileage or horsepower. In theory a hotter car runs more efficiently.
However, engine parts, oil, and gaskets will begin to fail at higher
temperatures. The use of colder thermostats isn't recommended unless
you really know what you're doing with a turbo or high compression
This page is more about the Do's and Don'ts of engine
cooling systems and how it works. The cooling system is there to
keep the engine at a steady operating temperature that is about
210F (99C). Without the cooling system the engine temperature would
continue to rise until the engine breaks apart.
The cooling system is comprised of a heat source (the
engine) that needs to be cooled, a water pump, a thermostat, a radiator,
hoses, an overflow tank, and coolant. The engine creates heat and
transfers that heat to the coolant that flows through passages inside
the engine. The water pump moves coolant from the engine to the
radiator. As the coolant passes through the radiator the ambient
air brings the temperature of the coolant down. The cooled coolant
is then pumped back into the engine to absorb more heat.
The purpose of the thermostat is to open when the
temperature of the coolant reaches the engine's operating temperature.
When the car is cold the thermostat is closed to prevent the coolant
from flowing. This makes the engine retain heat so it can reach
operating temperature quickly.
To test a thermostat put it in a pot of water and
heat the water. Measure the temperature of the water when the thermostat
opens. If it doesn't open at the temperature printed on the thermostat
throw it out.
The hot coolant is pressurized inside the engine.
The radiator cap specifies the pressure of the cooling system. Excess
coolant is bled off into the overflow tank.
Water pumps usually fail at the bearing. The water pump is a dirt
simple device. There is a cast aluminum plate that has a gear cog
on one side and a pump on the other. The bearing lets the pump spin.
Over time the bearing loses the grease packed into it. The grease
can be broken down from heat and displaced from coolant seeping
through the seal in the bearing. When the bearing is not lubricated
it will get really hot, expand, and seize up. The failure is often
sudden and the engine stops.
Change water pumps every time the timing belt or timing
chain is replaced, which is about every 100,000 miles for most cars
Do NOT open the radiator cap when the engine is hot.
The coolant is about 210 F and pressurized! Boiling hot water will
squirt out in all directions and cause severe burns.
Do NOT drive a car that is overheating! If the car
is overheating, pull over to the nearest parking lot and wait two
hours for it to cool down before driving it again.
Adding water to the overflow tank will NOT fix your problem! I've
seen a lot of people do this. Wait two hours for the car to cool
down, and add distilled water to the cooling system via the radiator
Do NOT ever use hose water, or tap water, or drinking
water, or mineral water! Use ONLY distilled water in the cooling
system. Minerals in the cooling system corrode the aluminum in the
engine head and radiator. This causes radiator leaks. The picture
above shows mineral buildup on the water pump and water pump gasket.
Does your car make gurgle noises when you turn it
off? You've got air in the coolant. With that much air, the coolant
can't flow. The car will overheat. Wait till the car cools down
(about two hours) and open the radiator cap. Pour in some distilled
water and antifreeze. Warm the car up till the cooling fans come
on and turn it off. Let the car cool down for two hours and then
fill it again with distilled water and coolant. You may have to
pinch the hoses to remove trapped air bubbles. Repeat the process
until the gurgle noises go away.
Do NOT dump used coolant down the drain! It is a sweet
tasting poison that can kill pets and wildlife.
I recommend changing the coolant every 15,000 miles or so, even
for extended drain interval coolant. As coolant ages it becomes
acidic and can even hold an electrical charge. This charge can change
the voltage of the engine temperature sensor giving a false reading
to the engine computer. Old acidic coolant destroys the aluminum
in the radiator and engine head.
After changing the coolant the cooling fan will run for shorter
periods of time. Go ahead and clock the cooling fan run time before
and after a coolant change. The difference can be measured in minutes.
This is because the new coolant is doing its job more efficiently.
Use the type coolant that the car manufacturer recommends! Chrysler’s
use green stuff, GM uses orange stuff, and some Euro cars use blue
stuff. Don’t ever mix it up!
Zerex is a Valvoline product that I use and recommend. Mix the
antifreeze and distilled water in a ratio that's appropriate for
the season and climate. This should be outlined on the back of the
antifreeze container or the car's service manual.
Not sure how much coolant to put in? Want to mix a 60/40? Pour
in 1 quart of antifreeze and 2/3 quart of distilled water. Repeat
this until its full.
I recommend using Prestone® Super Radiator Anti-Rust additive
and Water Wetter.
I also recommend flushing the coolant system several times with
distilled water to clear all the rust out of the system.
If there are grey globs floating about in the coolant
then that mean that engine oil is leaking into the coolant. This
is usually the result of a head gasket failure. Headgaskets should
be changed with timing belts every 100,000 miles. Some manufacturers
may recommend changing the headgasket at longer intervals, but I
wouldn't risk it.
Conversely, if the grey globs are in the oil, the
same failure is occurring.
Another strange and rare problem is a failure in the
temperature sensor. Old acidic coolant eats through the sensor and
can leak through the wire and to the engine computer causing electrical
shorts. I said it was rare.
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