A while ago, I wrote about brake fluid and how neglected it is. Coolant is a close second for abuse, and probably even more misunderstood.

How many times have you wondered what exactly was the difference between red, green, orange, or yellow coolant? Those are the common ones we see in the forklift industry, although Asian and European engines may also have blues and purples for factory fills. Unfortunately, there’s more going on here than “pretty colours” to complement underhood decor. To complicate it further, terms are used interchangeably: “long-life” coolant is not all the same, and they are not all compatible. So, what do we need to know to work with these systems?

One of these things is not like the other….

To start with, let’s take a quick look at the basics. What is antifreeze? It is composed of a base fluid (ethylene glycol or propylene glycol) plus an additive package: corrosion inhibitors, ph buffers, and sometimes extra lubricants to increase water pump longevity. The glycol base never wears out, but the additives have a limited lifespan. Coolant also gets dirty from corrosion and bacterial growth. When the additives are used up, acidic compounds form which attack metals and gaskets. A common cause of head gasket failure is acidic coolant.

So why the different colors? The dyes are added to help us avoid mixing incompatible additives.
The old green coolant we are familiar with had silicates added to prevent corrosion by coating the metals with a thin layer. While this worked ok, two issue arise: it isn’t as efficient at heat transfer, and the silicate lifespan is relatively short.
The red and orange coolants use a family of anti-corrosives known as organic acids. These are salts formed from neutralized acids. They are very effective at controlling corrosion, more efficient at heat transfer, and have a longer lifespan. However, when the additives reach the end of their lifespan, they rapidly turn acidic and cause problems in the engine. Early versions of these long life coolants led to lawsuits when consumers felt they damaged gaskets, but it was usually traced to improper maintenance.

Does it matter what type I use in my forklift?
Absolutely. Why? First, the coolants can’t be mixed because they do not work well together, and they can form sludge that clogs radiators. Also, the long life types are not all compatible with brass and copper radiators- they were designed with aluminum in mind. Some modern aftermarket suppliers have developed coolants that are supposed to be compatible with all other types, but it really does make sense to use the OEM’s recommended fluid. When you find mixed coolant colors the system needs a full flush and fill with the appropriate fluid. Also, don’t forget to check the ph level to ensure the coolant isn’t acidic. A quick smell can also let you know if it has bacterial growth. If it stinks, it goes. Be aware that tap water has contaminants, and you should be using distilled water if dilution is required.

One last note: specialized additives. Many larger diesel units will require a special anti-cavitation additive to prevent cylinder liner erosion. It can be measured with test strips and must be maintained within a specific range of concentration.

Don’t be slow to sell coolant servicing- it is critical to the long term health of any engine. If you need additional parts like thermostats, radiators, hoses, etc, check out this post first.

Share questions and thoughts in the comment section below.

Can we ask you for a favour? If you could think of just two friends who would like this content, please forward it to them. Or repost, tweet, or reblog it. Thanks. We really appreciate it.