Lets talk about your cars cooling system, basically it works just like the air conditioner in it transfers the heat from one place to another. The heart of the system is two parts, the THERMOSTAT whose job is to keep water in the RADIATOR as long as possible so the fans can remove the heat from the water and the WATER PUMP whose job is to keep the water moving. One overlooked part of the system is the RADIATOR CAP; its job is to keep the water under pressure, which raises its boiling point. As most of you know water boils at 102 degrees and the average operating temperature is 200 to 230 degrees. To keep the water from boiling we add ANTIFREEZE to further raise the boiling point well above what will ever be needed, usually a 50/50 mix of water and antifreeze. Most of the vehicles in production today use what is called "Closed Coolant Recovery" systems, which use a expansion tank or overflow bottle and allows the for the cooling system to vent when the pressure builds up past the radiator caps pressure limit. As the car cools down the coolant lost during the venting is sucked back in from the recovery bottle to keep the cooling system at the proper level and no or very little air in it. The other function of keeping the engine cool is for lower emissions and better performance

There are a few enemies to the cooling system that are very destructive over time and can cause severe engine damage.

SCALE: Forms from chemicals and particles in the water sticking to the brass and aluminum components.

AIR: In the cooling system air is nothing but steam which is 2 to 3 times hotter than the coolant and keeps the coolant from deteriorating and causing internal corrosion.

ELECTROLYSIS: Electrical current generated by submerged metals in coolant, which transfers particles of metal from one surface to another which causes corrosion and eventual leakage.

CHEAP REPLACEMENT PARTS: Inferior designs due to cost cutting procedures cause cavitation or foaming in the cooling system which severely limits the heat transfer process and flow of coolant.

Problems with the radiator usually occur from scale and sediment buildup blocking up the tubes or rows, which means that those rows are not dissipating heat cutting down efficiency. Also missing or damaged fan shrouds which are used to direct the airflow through the radiator and not around it. Aftermarket body kits and lowering vehicles which are all the rage also contribute to low airflow problems because they cutout some of the original design characteristics that helped force airflow through the radiator and into the engine compartment.

Below are some pictures of what happens when you neglect the cooling system.



Corrosion on the header panel of the radiator is rarely repairable.


This corrosion is caused by Extended life antifreeze being exposed to the air.



The picture on the right shows the thermostat installed backwards, this vehicle came in overheating and had blown the head gasket. If the thermostat is installed backwards, the hot coolant in the block will not heat up the thermostat because the sensing bulb is on the colder, radiator side.

I want to clear up a huge miss-information about thermostats, the higher the temperature rating on the T-Stat is, the cooler the engine is going to run. If you change a T-Stat from a 195-degree to a 160 or 180 degree you have shortened the amount of time the coolant will stay in the radiator and dump off the heat.


Antifreeze, so many colors, so many choices. The rainbow of different coolants that are now found in today’s vehicles has created a great deal of confusion among motorists, technicians and retailers alike. With so many different types and product choices, how do you pick the "right" antifreeze for a particular application?

The easiest answer to this question is to use a product that meets the OEM specifications for the vehicle or a product that is compatible with the type of antifreeze already in the cooling system.

Though colors and chemistries differ a great deal these days, most coolants contain ethylene glycol (EG) as their main ingredient. EG has long been used to prevent freezing and boilovers in automotive cooling systems. When mixed in equal parts with water (a 50/50 mix) EG protects against freezing down to -34 degrees and boilover up to 263 degrees with a 14-PSI radiator cap.

So if the main ingredient in most antifreeze is essentially the same, why is there so much disagreement and confusion over which product to use? The problem is that corrosion inhibitors used in antifreeze have changed in recent years, and different vehicle manufacturers have chosen different additive specifications for their vehicles.

Engineers can argue the merits of one type of additive package versus another, but the fact remains that the North American, European and Asian vehicle manufacturers have all opted to use very different coolants in their vehicles.

Up until 1996, Ford, GM and Chrysler all used standard "green" formula antifreeze that contained phosphate and silicate corrosion inhibitors. This kind of additive package provides good protection for cast iron and aluminum engine parts, as well as copper/brass and aluminum radiators. But the reactive nature of these additives means they usually wear out after two to three years or 30,000 miles of service. Consequently, the coolant has to be changed on a regular basis to minimize the risk of corrosion damaging the cooling system.

In 1996, General Motors began using a new extended-life antifreeze called Dex-Cool. The coolant contains a totally different kind of additive package called Organic Acid Technology or "OAT for short. The new additive package extended the life of the coolant to five years or 100,000 miles, (which was later extended to 150,000 miles). The new coolant was also dyed orange to distinguish it from ordinary green coolant. As time went on, other vehicle manufacturers began using extended-life coolants of their own. OAT-based coolants were soon being used by Ford, Chrysler and the European and Japanese carmakers. GM’s OAT-based coolant contains no silicates (GM’s engineers didn’t feel it was necessary), but Ford and Chrysler’s versions both contain silicates, making them "hybrid" coolants (HOAT). Ford’s HOAT coolant is dyed orange while Chrysler’s is dyed yellow. Mercedes also uses a HOAT formula, which meets the European "G-05" specification for a hybrid extended-life coolant. Late-model Audi and Volkswagen also use a HOAT or G-05 coolant, but their version is dyed pink. "Phosphate HOAT" coolants, on the other hand, are favored by the Asian carmakers. Honda’s HOAT coolant is dyed dark green.

Now you know why there is so much confusion over coolants. Similar products may or may not have the same color, so you can’t match coolants by color alone. You have to go by the additive formula in the coolant.

That brings us to "universal" coolants, a somewhat controversial class of products that are marketed as being suitable for all makes and models of vehicles, regardless of the color of the original coolant or its chemistry. These products are said to have a service life of five years or 150,000 miles, the same as other OAT and HOAT coolants in late-model vehicles. But there is an exception: If a universal coolant is used to top off an older vehicle’s cooling system that contains standard formula green coolant, the service life of the universal product is reduced to that of the original green coolant (2-3 years or 30,000 miles).

The appeal of a universal coolant is obvious because it simplifies the selection process and reduces the number of different antifreeze products stores have to stock. But opinions differ as to whether or not this approach really meets all OEM coolant requirements. Ford has recently stated that it cannot recommend any coolant other than those approved by Ford for use in its vehicles. Ford says universal coolants generally do not contain silicates and nitrites, both of which are required to meet Ford’s coolant specifications. Because of this, several major antifreeze suppliers do not offer a universal product and continue to sell three basic types of coolant, a standard green formula for older cars, an orange OAT formula for GM and a yellow HOAT/G-05 formula for Ford, Chrysler and the import manufacturers.

Another trend taking place is the growing popularly of premixed antifreeze. Motorists like it because it’s more convenient to use and costs less than full-strength antifreeze. There’s no mixing with water and no risk of contaminating the cooling system with minerals or salts found in ordinary tap water. Premix is also available in half-gallon and quart sizes for topping off cooling systems.


When do I change my oil

Freon changeover

Why did I fail my emission test

Wiring Diagrams 

• TSB's and Recalls



Timing Belts_ 1970-1997 Domestic & Imported Cars

Brake Squeals


Just For Laughs

Oxygen Sensors

Please feel free to contact me at the following address:

 E-mail: stberry@netzero.net


Last Updated on 4/20/2006
by Scott Throneberry