What about antifreeze that looks green in a bucket but when poured out or in drops takes on a reddish tint? Smells like antifreeze should. This came out of a Cummins NTC 335 engine in our GE 70 tonner. I can't figure out what is making the antifreeze appear red.

The colors of the non-antifreeze water treatment chemicals mentioned earlier were somewhat more consistent than the colors of different types of anti-freeze chemicals. There is unfortunately no 100% certain way to identify anti-freeze by color alone, as different manufacturers have used different dyes. I have seen ethylene glycol in yellow, orange, red, and green over the years, depending on who made it. Mixing different brands in an engine can generate all sorts of colors in between those. That is enough to greatly confuse any attempt to differentiate it from propylene glycol by color. The only way to be certain is to send a sample to a lab that provides analysis of coolants and have them identify it. The other alternative (often less expensive with smaller engines) is to drain the anti-freeze and flush the engine completely several times, until the flushing water comes out completely clean, and then install new anti-freeze so that you know for sure what is in the engine. Then be sure to document it so that in the future others can be certain of what you used.

Although fresh propylene glycol has much lower chronic toxicity than ethylene glycol, all antifreezes become contaminated with metals from exposure to the engine water pump, radiator, and cooling system during use, and any antifreeze, water with water treatment chemicals, or even flushing water, that has been drained from an engine should be considered hazardous and handled accordingly. It is much better to be safe than sorry.

PC

Let me stop you there. That statement is technically accurate, but misleading.

Propylene glycol is food.

Yes, food has a very low chronic toxicity. What is the chronic toxicity of the vegetables you're supposed to eat?

I know that's surprising. How can it be food when it's a glycol, and the other glycol is deadly toxic (and also sweet)? Well, it's the same as ethanol (wine) vs. methanol (deadly poison). Very similar chemicals, with a difference in the most minor of areas, but that's what it takes to go from 'food' to 'poison'. Biochemistry is full of idioms like this.

In industrial application, you may not care about ethanol vs. methanol or ethylene glycol vs. propylene glycol. Well, until you have a spill.

Why do we use one vs. the other today? That is a question which bears serious contemplation. I think you will find an interesting answer.


Well that's true, whatever the engine is made of, plus whatever the additives are made of, will be in the antifreeze. How bad is that?

The trouble is, "safe" gets pretty spendy pretty quick. I'd say it's valuable to first size up the "sorry" side of the equation before deciding how much to spend on "safe".

That's why ethylene glycol should be banned from your facility and you should throw completely over to propylene glycol. The cost is minimal to dispose of a whole lot of "sorry". As in "sorry we killed your beloved family pet", which is a VERY foreseeable outcome of a minor ethylene glycol leak on a locomotive.

Yes propylene glycol is very attractive to some living creatures, particularly bacteria. And an engine with a non pressurized cooling system and a large air exposed surface in the expansion tank can be a great place for bacteria to live. Another reason to handle any coolant that comes out of an engine very carefully.

PC

Well, if you add Ethanol to the propylene glycol........kill the bacteria and provide an energency source of refreshment to the crews?

dave

What kind of environmental threat does ethylene glycol pose other than poisoning small animals? Does it dissipate in the ground? Is it diluted by rain and runoff? With all the millions of autos out there with ethylene glycol, and some of them leaking it, I've not heard of any hazmat warnings about the stuff other than as pet poison.

Leakage of ethylene glycol onto highways gets diluted into the rain and runoff, and it gradually degrades in a complicated chemical process that yields acetate and methanol. Ethylene glycol is poisonous as Robert pointed out earlier, ingestion of 100 mL (and sometimes less) can be fatal to a human.

PC

OK from a guy still firmly entrenched in the Imperial system of measurements, how much is 100 ml?

Not very much at all. A little more than 1/5th of a US pint.

PC

http://www.raypak.com/afreeze.htm
Propylene glycol is marginally better at heat transfer (at same concentration).
Requires slightly more concentration (5% @ 50%) of propylene glycol to achieve the same freeze protection.

Ethylene glycol spills must be reported under SARA Title III. Not propylene glycol.

http://www.imcool.com/articles/antifree ... sposal.php

Are the two coolants compatible with each other? If I switched to PG would I have to completely flush my systems of the EG first?

They are chemically compatible but if you do not flush the engine cooling system you may end up with pockets of Ethylene Glycol left in the oil cooler, water pump housing, block water gallery, and radiator headers that could contaminate the new charge of Propylene Glycol.

PC

Now what is that pink colored antifreeze that GM uses? I've heard nothing but bad news surrounding the use of that fluid. That isn't PG is it?

A little bit of research revealed this:
http://en.wikipedia.org/wiki/Antifreeze

Its turning out that as with all other "safe" alternatives, the safe alternative isn't as good as the original article.

"Propylene glycol oxidizes when exposed to air and heat. When this occurs lactic acid is formed.[2][3] If not properly inhibited, this fluid can be very corrosive.[citation needed] Protodin is added to propylene glycol to act as a buffer, preventing low pH attack on the system metals. It forms a protective skin inside the tank and pipelines which helps to prevent acid attack that cause corrosion.

Besides cooling system breakdown, biological fouling also occurs. Once bacterial slime starts, the corrosion rate of the system increases. In systems where a glycol solution is maintained on a continuous basis, regular monitoring of freeze protection, pH, specific gravity, inhibitor level, color and biological contamination should be checked routinely."

I don't like the sounds of that. I don't need yet another duty to perform, regular checking the status of the antifreeze in our diesel engines is not an effective use of my time. I also don't like that it has the potential to cause internal corrosion.

Here is a good FAQ on antifreeze and a reference chart:
http://www.eetcorp.com/antifreeze/antifreeze-faq.htm#q8
http://www.eetcorp.com/antifreeze/Coolants_matrix.pdf

I think in my case I will stick with the heavy duty ethylene glycol in our diesel engines. The safety benefits of PG do not outweigh the potential risks and increased maintenance. Anyways if the cooling system is tight and filling/draining is done with care very little antifreeze will be exposed to the environment.

And I think in my case I will stick with what the engine manufacturer recommends for use in the engine, since they all have published specifications for coolant. EMD MI 1748 for 567s, 645s and 710s, CAT SEBU8223 for 3500's, etc. etc.

PC