Engine coolants

[philip]

Coolant is coolant, right?

Mix it 50/50 for all but the most extreme temperature boundaries and you're ok, right?

Somewhere in the background, we've all heard something about dissimilar metals protection and cavitation. Big yawn unless again, you are operating out of the mainstream.

So, I'm posting portions of an article from a Ford PowerStroke offroad site with the more salient parts that also apply to our SD engines.

"There are three basic types of coolant: Ethylene Glycol (EG), or conventional coolant, is typically green; Long Life, or Extended Life, Ethylene Glycol is typically yellow; and Propylene Glycol (PG) is typically red and sometimes referred to as "non-toxic" coolant."

"PG coolant is not recommended for Power Stroke Diesel engines. Because of its chemical makeup, PG coolants can cause damage to aluminum parts, gasket materials and certain kinds of hoses. It also has a lower boiling point than EG coolant, usually 10 F to 15 F lower. While it may not sound like much, in a modern cooling system with a high output engine a few degrees may make all the difference in the world. Coolants that are methyl alcohol or methoxy proponol-based should also never be used."

"Extended Life Coolant

Extended life coolants are available for newer model diesel engines (2002 model year). Extended life coolants provide a longer service interval under normal conditions, because they don't require the addition of supplemental coolant additives (SCA). These new coolants use advanced organic acid technology, which depletes much more slowly than traditional coolant additives, to protect the engine."

"Cavitation Protection and SCAs

SCAs provide cavitation protection for conventional green coolant. Cavitation is erosion that occurs on the outside diameter of the cylinder wall, and can happen if vapor bubbles form in the cooling system and attach to the wall.

Every time the pistons move up and down, they rock in the bore, causing the cylinder wall to vibrate. Vapor bubbles can form on the outside of the cylinder wall as it moves inward, or away from the coolant, creating a low-pressure area. When the cylinder wall moves outward, or into the coolant, the pressure increases on the vapor bubbles. After many cycles, vapor bubbles continue to form and the pressure on the bubbles increases until, finally, a vapor bubble collapses. When this happens, it creates a localized stress area of more than 50,000 psi. The high pressure and heat created by the implosion removes a small amount of cylinder wall material where the vapor bubble was attached. Over time, the cylinder wall can continue to erode, and eventually may form a pinhole in the wall that allows coolant to enter the combustion chamber, leading to possible engine failure.

Unlike diesel engines, gas engines do not need cavitation protection. This is because diesel engines are more likely to be used in heavy-duty applications and operate under higher loads for longer periods of time. By nature, diesel engines often have cylinder pressures greater than twice the cylinder pressure of a gasoline engine. This combination of high load and high combustion pressures creates the violent cylinder wall vibrations that lead to cavitation. Most gasoline engines will not experience enough of this kind of operation in its life to cause a failure. Although rare, there have been occurrences where a gasoline engine did fail from cavitation erosion.

You can protect your diesel engine from cavitation by adding the proper amount of SCA to an EG cooling system. When used properly, SCAs help neutralize acids and provide anti-foam protection as well as prevent cavitation, scale and general corrosion. SCAs work to prevent cavitation by forming a protective coating on the cooling system surfaces. This coating will provide a barrier between the cylinder wall and the vapor bubbles. The vapor bubble implosions erode the SCA protective coating instead of the cylinder wall."

"Maintain a 50/50 mix using distilled water. Water that has minerals in it (or hard water) must not be used. The minerals will lower the boiling point and can increase corrosion in the system.

Under normal driving conditions, the green EG coolant should be changed at 48 months or 50,000 miles for the first time, then every 36 months or 30,000 miles every time after. SCAs must be added and maintained with this coolant."

[asavage]

"There are three basic types of coolant: Ethylene Glycol (EG), or conventional coolant, is typically green; Long Life, or Extended Life, Ethylene Glycol is typically yellow; and Propylene Glycol (PG) is typically red and sometimes referred to as "non-toxic" coolant."

So far, so good. Except the colors generalization. For example, Prestone's Gold fits-all formulation is yellowish, and it's not particularly long-life or extended life. And Ford has been running a yellowish phosphate-free coolant for several years that is a hybrid coolant, also non-EL.

"PG coolant is not recommended for Power Stroke Diesel engines. Because of its chemical makeup, PG coolants can cause damage to aluminum parts, gasket materials and certain kinds of hoses.

This has the ring of untruth about it. While I am not a fan of propylene glycol, AFAIK (and I have spent some time researching coolants) none of that last sentence is true. Conversely, it's been the OAT coolants (Dex-Cool, specifically) that have been accused of softening some rubber parts (like intake manifold seals). It may even be true.

"Maintain a 50/50 mix using distilled water. Water that has minerals in it (or hard water) must not be used.

Entirely agree. If you've ever distilled you own water (I have an old Sears distiller unit), you know how much crap is in water. Crap that is good for drinking, not good at all for batteries and cooling systems.

The minerals will lower the boiling point and can increase corrosion in the system.

Minerals increase corrosion? AHAHAHAHA! I suppose large enough minerals (like rocks) could accelerate impeller wear.

Under normal driving conditions, the green EG coolant should be changed at 48 months or 50,000 miles for the first time, then every 36 months or 30,000 miles every time after. SCAs must be added and maintained with this coolant."

The generic, industry advice is 36 mos. to the first coolant change, 24 mos. after that. Maybe Ford has extended this period for the late PS engines. But if'n it was mine, I wouldn't wait four years for the first change. I've drained and flushed too many cooling systems. And a PS is too expensive to R&R the heads on.

Also see a previous post of mine on coolants.

What do I use? Distilled water & Chevron Dex-Cool compatible: and Extended-Life coolant that does not have to be flushed every two years on our old engines.

[Knucklehead]

You can protect your diesel engine from cavitation by adding the proper amount of SCA to an EG cooling system.

While the above information from the offroad site is correct, it is incomplete in relation to SCAs (supplimental coolant additive). If anyone is adding them they need to be careful. It's not something that you just pour in, and more is definitely not better.

I'm not a cooling system tech, but having used SCAs in class 8 diesel tractors for a few years I've learned some things expensively. From the perspective of an SCA user, there are three kinds of antifreeze:

Regular automotive stuff
Low silicate (hard to find)
Fully formulated (or extended life as the previous article calls it)

Regular automotive AF (anti-freeze) has something in it called silicates, which inhibit corrosion wonderfully, protecting aluminum particularly well. But silicates fall out of solution kind of easy and SCAs make things worse by adding silicates beyond the saturation point, which can lead to a lot of junk in your radiator, so they make a low silicate AF for use with SCAs. If you use fully formulated AF it already has an SCA.

Whether you use fully formulated or mix your own, it has to be checked every..., hell I don't know, I do it every oil change (monthly) but every six months would probably be ok, or if you add anything to your cooling system. You do this by using test strips. You'll need at least a couple; I bought a bottle of 50. The SCA ratio is about 3%. If you use too much it can ruin your radiator by damaging the solder and brass among other things. A radiator in my big truck is $1000, and that doesn't include the price of lots of labor required to change it. I have learned to watch my SCA level closely.

Here is a picture of a big Cummins liner with some cavitation. It has over a million miles on it so that's not bad.



Also, unrelated to the use or nonuse of SCAs, here is a picture of scale build up in the SD oil cooler. Maintain your cooling system!



It is debatable whether the SD22 needs an SCA. I would imagine it is considered a light duty application, especially being naturally aspirated, and I don't think car diesel engines require them, but I am open to be corrected on that (I'd like to hear one way or the other). It certainly won't hurt, but if you're going to add an SCA, it must be used correctly.

It should be noted that SCAs come in two types mainly; I have always used the same one so I don't know the details of the other, but they are both good and best if not mixed. Pick one and stay with it, and don't use cheap imitations.

I personally use Fleetguard SCA, Redline WaterWetter, and the lowest percentage of antifreeze necessary for my climate, which in Phoenix is about 10%. At such low percentages I can use regular AF without worrying about the silicates. The SCA provides all the other protection necessary.

[philip]

SNIP- Whether you use fully formulated or mix your own, it has to be checked every..., hell I don't know, I do it every oil change (monthly) but every six months would probably be ok, or if you add anything to your cooling system. SNIP

Galen, being as you live in Phoenix, an area KNOWN for highly mineralized tap water, you did not mention using distilled water when flushing and when mixing up a new batch of coolant.

I also noticed a mention of Redline's "Water Wetter" product.

[asavage]

The SD is a dry-liner engine. I don't think cavitation is an issue. But plain old corrosion is.

Silicates coat, and they wear out, so must be replenished, either by changing the coolant that carries them or by adding more silicates. I prefer to flush the system and change the coolant, because under normal conditions a lot of crap gets into the coolant anyway: minor head gasket leakage is considered normal and lowers the pH of the coolant, casting crap does come off an get carried around, helping to plug steam holes and encourage impeller wear, some oxidation occurs even with corrosion inhibitors, etc.

Extended use (long life, OAT, HOAT, etc.) coolants don't depend upon silicates/phosphates/boron etc as their primary corrosion inhibition. A back-channel source in the industry tells me very good things about some long-life coolants and heavy diesel engines, so I'm not afeared to run SCA-less in my diesels.

[Knucklehead]

The water here is so bad I have to wash it off if it gets on something. If I don't want it on the outside of the truck, I sure don't want it on the inside. Sorry, I take using distilled for granted.

[asavage]

I lived in Phoenix from Jun-80 to Feb-81 (actually, Tempe & later Mesa, but I commuted into Phoenix). Baseline was the only place that had things that vaguely looked like "trees" to me, coming from the Pacific Northwest

As a young pup, I worked at a motorcycle shop (not in AZ), and rode them everywhere. Phoenix was where I got run over by a drunk driver, an incident which profoundly changed the course of my life, as you might imagine. I didn't ride nearly so much afterward. Hell, for a long while I could barely walk. Couldn't break out of a shuffle for a year.

Yeah, I know about the water. Does the phrase, "Salt River Project" have meaning for you? I recall the water coming out of the tap and foaming in the sink back then.

And, quoting statistics I learned while I was there, that area has four times the national average of dust particulates in the air.

(Phil adds) "Desert Lung" is a form of irreversible emphysema caused by an accumulation of air born silica (sand) in the lungs.

[ecomike]

Regular automotive AF (anti-freeze) has something in it called silicates, which inhibit corrosion wonderfully, protecting aluminum particularly well. But silicates fall out of solution kind of easy ..... (snip) which can lead to a lot of junk in your radiator .... (snip) I personally use Fleetguard SCA, Redline WaterWetter, and the lowest percentage of antifreeze necessary for my climate, which in Phoenix is about 10%. At such low percentages I can use regular AF without worrying about the silicates. The SCA provides all the other protection necessary.

A couple comments and corrections, one is that propylene glycol (or polypropylene glycol) actually has a higher boiling point that Ethylene glycol. The ford article had several errors, but Al nailed most of them already.

I am finding it difficult, recently to find the old style antifreeze! I was based mostly on sodium silicate ( SS) and ethylene glycol (EG). The SS was a multipurpose additive, an excellent corrosion inhibitor, and leak sealant, and an acid neutralizer all in one chemical compound. The EG raised and lowered the boiling point. Most of the problems with crud in the cooling systems was caused by acidic exhaust gases leaking into the cooling system and by hard water added to the overflow bottles by ignorant car owners.

The silicates do not fall out of solution easily, they do fall out by reacting with hard water salts like calcium and magnesium from tap water to form concrete boiler scale, or by reacting with acid to form solid silica which also precipitates, but only precipitates when the coolant mix hits a critcal pH! The more sodium silcate you have (up to the solubility limit) the more acid it can neutralize before that critical pH is reached!

The trick is to avoid reaching that critical pH, not limiting the amount of silicate or antifreeze you start with. My brother ran >80% antifreeze in his 79 Ford Torino for about 15 years, just topped it off with straight antifreeze, never lost a water pump or radiator in over 150,000 miles and 15 years with that Torino. I usually replace my rubber coolant hoses about every 4 years, and I replace the coolant that drains out at the same time with the fresh, old EG/SS formula antifreeze at a 50/50 mix with DI water, but I have not flushed a radiator or block in over 20 years now, and I only replaced radiators on used cars that I bought where the PO had already killed them.

The new, long life coolants seem to have eliminated the silicates, so I only buy antifreeze now that lists the silicates on the ingredients label as I am not prepared to trust mixing the old with the new, just too much different new formula stuff running around right now and I have heard warnings about some of them, like Dexcool having problems.

Lastly, silicates are totally environmentally friendly.

[asavage]

Mike, the evidence of silicate precipitation in OTR trucks is too numerous to ignore. Adding too much SCA will cause solids to form, regardless of pH.

Glycol concentrations > 50% level recommended causes the boiling point to lower -- significantly. Go find a chart, it's a large drop when you reach above 70%, IIRC.

Lastly, the ability of silicates to "coat" and protect surfaces degrades with time, which is why everyone who recommended them back in the day also recommended flushing the old out and replacing the coolant. The typical service interval was 30k, but some as low as 24k and some as high as four years.

The glycol doesn't degrade in the cooling system, and the freeze/boil point will not change over time until the silicates die off, corrosion forms, and the added oxides in solution depress the freeze point further -- yes, "bad" coolant actually protects to a lower temperature! Meanwhile, scale forms, electrolysis eats up things and the heater core's efficiency drops off due to low-flow crap settling in it.

I like extended life coolants, and I run DexCool (OAT) coolant in everything I own. It does not degrade even as much as the mfgrs state. I have yet to see coolant leakage on my rigs -- a small sample, granted. If the problem you are referring to WRT DexCool is with GM vehicles (esp. intake manifold seals), there is evidence that the problem is not coolant related -- though we had changed dozens of intake seals leaking DexCool, this is kind of "GM at its finest" engineering. Materials compatibility is one thing, sloppy mfg tolerances is another.

Finally, again: all cooling systems have less corrosion if air can be kept out of them. Even small amounts of air can greatly increase the rate of corrosion.

[ecomike]

I have never used SCA, so I can't really comment on it. The point I was trying to make is that I have never used SCA, just 50/50 old style silicate based antifreeze plus DI water with no flushes, just partial replacement when I replace aging hoses on about 4 year intervals. Hoses don't last long down here in this hot Houston weather. Never lost or needed to service a heater core in my life. Then again freezing weather here is about +40 F, LOL. The other point I was I trying to make is that too little silicate, like just 10% antifreeze, can lead early pH drop, pH failure and thus precipitation of the silicates in the radiator and heater core tubes.

The maximum boiling point is at 70% antifreeze, 276 F. At 50% it is 265 F. What you are recalling is that the antifreeze does not have the high rapid thermal conductivity of water, so there is trade off between the concentration and thermal properties of the two. The more water, the more rapidly heat is conducting from the liquid coolant to the metal radiator, but raising the boiling point also increases the rate of thermal transfer, another trade off. I have never done all the thermo calcs on it, but IIRC they recommend 50/50 blends as the optimal, most efficient thermal formulation for maximum heat transfer.

The real reason for the frequent drain interval was to avoid the sudden drop out of silicates caused by reaching that critical pH which is caused by the silicates neutralizing acids. The glycols do actually slowly break down over time at high temperature when exposed to metal catalysts and oxygen, forming weak carboxylic acids which are then neutralized by the alkaline silicates. CO2 forms carbonic acid which reacts with the silicates reducing the pH too.

Very interesting feedback on the DexCool, I will keep that in mind for sure. What is OTA?

Agreed, air is bad for coolant, but good for us and good for external cooling!