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Coolant 411


2grimjim

Just added an Athena 300 kit on my 2016 Yamaha YZ250X, and after draining the stock blue colored coolant, what drained out wasn't nearly enough to refill with the 300 top end. So.... this is what lead to my quest about coolant color coding, types, and compatibility.

 

When I worked as a Yamaha/Suzuki/Polaris service tech, It never really crossed my mind. The coolant that Yamaha and Suzuki were sometimes blue, sometimes pink, and sometimes yellow. Polaris was (is) always looked like the same green stuff sold at auto parts stores. But, the service replacement coolant sold by Yamaha and Suzuki were always Green. When I asked our Yamaha and Suzuki Service Representatives what the difference was between the OEM and the replacement green coolants, the both had the same reply: "Coolant should be replaced every 2 years. If the coolant is low, advise your customers to drain and flush the cooling system and replace the coolant with what you stock on your shelf."

 

Hmmm.... Ok. Still didn't answer my question, but I'll just do what the man says.

 

Turns out there are significant differences between coolant types. Most of the changes have been made in the last 20 years but prior to that, you had one choice. The green stuff.

 

Now, as of today, you have 3 general classes of coolant (excluding running straight water or waterless coolant).

 

They are as follows:
Inorganic Acid Technology (IAT)
Organic Acid Technology (OAT)
Hybrid Organic Acid Technology (HOAT)

 

Inorganic Acid Technology

 

IAT is what we all know as the classic green coolant that has been around for ages. It is a mixture of either Ethylene Glycol (toxic) or Propylene Glycol (non-toxic, the same stuff in your Mio), and corrosion inhibitors containing phosphate and silicate acids.

 

Now, before I go any further, I'm going to clarify what exactly "Silicates" are. Silicates are not the same as Silica. I've read a ton of nonsense about coolants containing Silica and it being used to "scrub the insides" of your engine. This is a bunch of B.S. Coolants have never contained Silica.
Silicon is an element (like Oxygen, Nitrogen, and Carbon). In its pure form, it's used to make chips for electronic circuits.
Silica is Silicon Oxide (SiO2). It's the mineral Quartz and the largest component of beach sand. Silica is not soluble in water.
Silicone is a synthetic rubber that replaces Carbon with Silicon.
Silicate(s) are an anionic Silicon compound. Various types of Silicates are water soluble compounds that are acidic, hence their use as a corrosion inhibitor in coolants.

 

There is endless (incorrect) writings about how Japanese manufacturers don't use coolants with Silicates because the Silicates will grind up water pump seals. Nonsense. Japanese manufacturers don't use Silicates because they believe that Silicate compounds are too chemically aggressive and given the right conditions, will cause excessive pitting in the areas of highest heat (near the exhaust ports).

 

Phosphate and Silicate corrosion inhibitors in green coolant are considered 'fast acting'. They provide a nearly instantaneous barrier to the bare metal internal surfaces but are consumed quickly in this process. IAT coolants must be replaced every 2 years. After 2 years, the coolant my still have it's boil-over and freeze protection, but it's ability to prevent corrosion is gone.

 

IAT coolants are NOT sold as 'long life' coolants. In order to be considered 'long life', the coolant needs to have a corrosion inhibitor package good for 5 years.

 

There are 'low Silicate' and 'Silicate free' brands of coolants available the appease the Japanese manufacturers. Just as there are 'Phosphate free' brands for European brands (Zerex G05 is a Phosphate free HOAT coolant). Low Silicate types are usually sold as 'universal coolants' and advertised that they can be mixed with any type coolant (but they reduce the lifespan of any long life coolant to 2 years)

 

Zerex makes an "Asian Formula", coolant that contains Phosphates but no Silicates. It is available in Red and Blue. The formulation is the same for both, there's just a choice of colors for the anal compulsive.

 


Organic Acid Technology

 

OAT coolants started life with GM's Dexcool in 1996. They are usually orange. As fo 2013, both GM and Ford use Dexcool. OAT coolants do not use Silicates, Phosphates, Borates, Nitrates, Nitrites, or any other type of fast acting, agressive corrosion inhibitor. The ingredients are proprietary. The advantage with OAT coolants is they offer protection against corrosion for 5 years. However there is a problem with Dexcool and GM was sued over it. The brilliant engineers at GM did not test the Dexcool additives for compatibility with the Nylon 66 used in for the intake manifold gaskets used in most everything they built. Given the right conditions, the Dexcool would soften the Nylon and create a coolant leak into the intake ports.

 

OAT (Dexcool) coolants should NEVER be used where the manufacturer didn't use it from the factory. GM allegedly changed the specification for Dexcool after they were sued, but the potential still exists for incompatibility with certain elastomers used in gaskets, seals and o-rings.

 


Hybrid Organic Acid Technology

 

HOAT coolants were a response by manufacturers other than GM that wanted the long life coolant but were concerned about protecting against corrosion while using a less aggressive OAT component. The HOAT coolants used by manufacturers used organic acid inhibitors that were less susceptible to attacking plastics and rubbers but were not as effective at providing initial corrosion protection. All HOAT coolants add some inorganic acid compounds to make up the difference. Ford switched to a HOAT specification between 2003 and 2004 model years without any changes to cooling system components, gaskets or seals. Zerex G05 is a HOAT coolant that contains some Silicates. HOAT specifications for most Asian manufacturers will contain Phosphates but not Silicates, HOAT spec for most European manufacturers will have Silicates but no Phosphates. European manufacturers do not like to use Phosphates because of hard water issues in Europe. The Phosphate corrosion inhibitors will react with hard water and cause precipitates (coolant sludge).

 

Many Industrial, commercial, and heavy duty diesel manufacturers specify HOAT with Borates, Molybdates, Nitrates, or Nitrites to combat cylinder liner cavitation pitting.

 

All coolants advertised as 'Long Life' will be either OAT or HOAT formulations.

 

 

Now, what does all this business mean with my dirt bike?

 

The color, unless it's orange or green, color is pretty meaningless. Japanese no-Silicate coolant can be pink, blue, or red.

 

There are several universal coolants (Prestone makes one) on the market that will work with any coolant type if you are worried about topping off your OEM factory fill.

 

Japanese manufacturers in general specify a coolant type with little or no Silicates.

 

European Manufacturers in general specify a coolant type containing no Phosphates.

 

No European or Japanese manufacturer recommends the use of Dexcool or a straight OAT type coolant. And Honda and Toyota specifically prohibits Dexcool in any of their vehicles.

 

As far as Polaris, and Arctic Cat (I know, not motorcycles), you are probably safe with any green coolant. But knowing how most ATV's and UTV's are used, a universal long life would probably be a better choice. Universal long life coolants are usually a HOAT type.

 

 

So, how do I know if my coolant corrosion inhibitors are depleted?

 

If you replace your coolant every 2 years, you don't need to worry about it. But, if you must know, there are 2 tests you can do to check if the corrosion inhibitors are still working. The 1st test is to use a voltmeter. Remove the radiator cap, place the ground probe on the frame (or battery ground cable if you have one), and the positive lead inside the radiator immersed in coolant but not touching the radiator, and observe the voltage. It should be less than 0.3V (300mV). I'm not 100% convinced that this test is an accurate indication. My preference is to use wide range pH test strips. Old school coolant can range between 10.5 and 14. Newer long-life coolants will be between 8 and 10.5. In all cases, if the pH is anywhere near 7 (or below), the corrosion inhibitors are dead.

 

What about Redline Water Wetter, Maxima Coolinol and Cool-Aid, Engine Ice, and Evans waterless?

 

A water-only option without any corrosion inhibitors is just plain stupid. Even distilled water will cause corrosion in a short period of time. Hard water will cause corrosion damage very quickly. Even running straight water with a corrosion inhibitor additive (Redline Water Wetter, Maxima Cool-Aid) won't do much in the way of keeping your engine cooler. How cool the engine runs is determined by the heat rejection rate of the radiator as well as the coolant type. Pure water may have a higher capacity to carry heat, but the radiator can only get rid of that extra heat load at a certain rate. That rate is determined by the radiant area, the difference in temperature between the ambient air passing through the radiator and the coolant inside, and how fast the coolant is traveling through the radiator. Running straight water will require the water flow slower through radiator to allow for the extra BTU energy to be rejected, but slowing the rate through the radiator is going to mean the rate will be slower through the engine. And this will raise the temperature of the water even higher. A run away is then in effect. Most stock cooling systems have enough reserve cooling capacity that this isn't a big problem or even noticeable, but it lowers the threshold where boil-over occurs.

 

Waterless coolants have the same heat rejection issue but for a different reason. Pure ethylene glycol doesn't have the heat capacity of water and since the rate of heat transfer is slower to the coolant, the engine temperature raises. And because the waterless coolant rejects less heat to the radiator, it doesn't cool as much. Operating temps 20+ above what most dirt bikes are designed for is going to cause issues with detonation, oil cook-off, seal life, clutch life, and who knows what else.

 

There is one scary aspect of waterless coolant: it doesn't boil until 385 degrees F. You will pretty much destroy your engine if you manage to bring the temp up to 385 degrees. Having a water based cooling system on a dirt bike is like having a temperature gauge. When the coolant boils and clouds of steam start rolling out the overflow, its telling you to shut the bike down. No warning like that with Evans. Just a seized motor.

 

Manufacturers do a pretty good job of sizing the cooling systems on modern dirt bikes so any playing around with straight water or waterless coolant is going to push things out of balance. 50/50 water/ethylene glycol is what they are designed for and that's what I use.

 

One last note. I've stopped using all of the motorsports industry brand coolants. I think all of them are OK if you change the coolant several times a year, but I'm pretty sure they are all lacking to varying degrees on the amount and quality of corrosion inhibitors blended in them. I've been pretty disappointed on the lack of corrosion control with all of them.

 

Oh, and I settled Zerex Asian Formula (Silicates free) coolant on my Yamaha. With a 21psi cap, not a hint of overheating on a 90 degree day crawling up slow, steep rocky trails.


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