Curbside Clueless: Additives: Snake Oil or Magic Elixir? Part 2 – Cooling System Additives

In part one we started our discussion of additives with those for the fuel system. Considering Paul’s recent post on his Subaru passing the 150K mark and comments about the tendency of head gasket issues, I figured cooling system additives would be a good place to go next.

Cooling system additives also come in a number of basic flavors.

Flush: These are intended to be used before installing new antifreeze. Most of the products on the shelf in this category, at least in the US, are pretty mild and won’t have much affect on a really dirty system. It you live somewhere that you can still get flushing products that come in two bottles the flush and the neutralizer they are usually the strongest and might clean up that system that hasn’t been changed in say 15 years. However if there really is that much corrosion in the system that might be the only thing holding stuff together so just like power flushing consider the risk before you go with the more vigorous chemicals or methods.

Or you can try some household products to clean your cooling system.

Anti-rust and water pump lube: These are often times sold as a combo product. The anti-rust is either something that will neutralize existing rust or just some sort of oil that the tout as lubricating the water pump. The thing is that the bearings in a water pump or sealed from the liquid side of the pump, so at most they could lubricate the seal. The problem with the products containing oil is that cooling system hoses are not designed for use with oils.

I personally use a product on one of my wife’s cars. The cooling system was pretty neglected when we bought it so after flushing, replacing the thermostat and hoses I added some anti-rust/water pump lube. Within a few weeks I was replacing those hoses again as they were now very soft from the oil in that product. On some late model cars that have a rubber seal in the valve of the thermostat could experience problems. So I shy away from these products completely now.

Water wetter/super coolant: These products claim to make your car run up to xx degrees cooler. They work on the principle that if you reduce the surface tension of the coolant it can transfer heat better. However many of those products say they recommend using it with pure to no less than 60% water. The dirty little secret is that ethylene glycol is not that good at transferring heat, water is actually better. For example I have seen in Ford owner’s manuals where they state that while 50/50 is the normal recommended ratio for exceptionally cold climates 40% water 60% antifreeze can be used and in particularly hot weather or high load situations to use 60% water and 40% antifreeze. For the most part these additives are more band-aids than anything else. If you need one of these products your cooling system is not up to snuff. The system may be partially plugged due to neglect, you are exceeding the designed rating of the vehicle or you’ve upped the power level of the engine without a corresponding increase in cooling capacity.

Stop leak/sealer/coolant “conditioner: Often times you’ll hear people state that these will plug up your radiator or heater core. Some of them seem to be more prone to that than others. Many times it is the overall neglect of the system that resulted in the leaks is also the likely reason the blockage started. I also believe the different types of sealers are more or less prone to cause problems. Ones that seem to work on the same principle as  adding black pepper to the system, particles that are large enough to act as the finger in the dyke will often do the trick on small leaks in gaskets, radiators, and heater cores. They aren’t very effective in sealing water pump and leaks to the combustion chamber. Often times these come as a powder, tablet or a liquid with a fine powder floating in it.

GM recommends their “coolant conditioner” tablets be added at each coolant change for many of the Cadillac and some other engines. Subaru recommends their “conditioner” with each coolant change for a number of their engines. The one in Paul’s is an example. Some of the Subaru head gasket failures are external leaks. In my research I came across this info on the Scooby Enthusiast forum that the the active ingredient in the Genuine Subaru conditioner is linseed meal. That’s the chunks on the paper towel. In addition there are some of the same corrosion preventives as used in regular antifreeze. So it is likely that Paul’s Subaru received a dose with fresh coolant when its water pump was replaced.

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