T. Freeland 09/15/2002

Yeah, I know, Corvairs and Volkswagens are air-cooled. Now that that is settled, most other powerplants air liquid cooled.

Fact #1 - Water is a better coolant than antifreeze. It has better heat capacity, and it conducts heat away from your block and heads better than antifreeze, and conducts it out through the radiator better as well.

Fact #2 - Water is the most expensive coolant you will consider using. It promotes corrosion and freezes at higher temperatures and boils at lower temperatures than other substances you would choose as a coolant. Therefore, do not use plain water.

Water has such a good heat capacity, that you are not going to improve upon that attribute, but what can we do with it's other attributes? Antifreeze to the rescue. It inhibits corrosion, raises the boiling point, and lowers the freezing point. These are good things. Most antifreeze is based on ethylene glycol (HOCH2CH2OH for you chemists). It is poisonous, and attracts animals, so don't drain it in the street and protect your kids from it. If swallowed, give 2 glasses of water and induce vomiting, call a physician.

Antifreeze Freeze Protection Table
Total cooling system capacity <------------------------------------------------------------Total Amount of Antifreeze in System----------------------------------->
3 quarts 4 quarts 5 quarts 6 quarts 7 quarts 8 quarts 9 quarts 10 quarts
8 quarts -7 -34 -68 === === === === ===
9 quarts 0 -21 -50 -84 === === === ===
10 quarts 4 -12 -34 -62 -84 === === ===
11 quarts 8 -6 -23 -47 -69 -84 === ===
12 quarts 10 0 -15 -34 -58 -74 === ===
13 quarts 13 3 -9 -25 -45 -66 -84 ===
14 quarts 15 6 -5 -17 -34 -53 -74 -84
15 quarts 16 8 0 -12 -26 -43 -62 -76
16 quarts 17 10 2 -7 -19 -34 -53 -68
17 quarts 18 12 5 -4 -14 -27 -43 -59
18 quarts 19 14 7 0 -10 -21 -34 -51
19 quarts 20 16 9 2 -7 -16 -28 -42


Boiling Point

Boiling Point of Coolant with Varying Percentages of Ethylene Glycol @t Atmospheric Pressure & @ 15 P.S.I.

  Atmospheric 15 PSI (103 kPa)

% E.G.

B.P. C B.P. F B.P. C B.P. F
0 100C 212F 120C 248F
33 104C 219F 125C 257F
44 107C 224F 128C 262F
50 108C 227F 129C 265F
60 111C 232F 132C 270F
70 114C 238F 136C 276F

Do not use a mixture greater that 70% (68% is max. freeze protection) ethylene glycol unless the manufacturer recommends it.

The pressure of the coolant affects the boiling point.

Effect of System Pressure on Boiling Point


0 psi 4 psi 8 psi 12 psi 16 psi  20 psi 24 psi
Water 212F 225F 233F 242F 252F 260F 265F
33% 220F 230F 240F 253F 260F 268F 273F
44% 224F 234F 245F 257F 265F 272F 279F
50% 226F 236F  248F 259F 267F 275F 280F
60% 231F 241F 253F 264F 273F 280F 285F

There are various anti leak preparations that can be mixed into the cooling system to prevent leaks or repair them. Sometimes they are successful, sometimes they are not. Some people wonder if these preparation might not clog the cooling system or impair it's performance. One popular brand is made of aluminum powder and claims to lubricate the water pump. I believe that claim to be a little bizarre, I don't see anyone selling aluminum powder as an oil additive! However, it is fairly effective at stopping leaks most of the time. As far as harm goes, I suspect that most of these additives are relatively harmless, otherwise they would be subjected to many lawsuits and would not remain in business long. I have used pellets made by Barr's Leaks with great success - general motors equips many of it's vehicles with it from the factory.

There is also propylene glycol antifreeze. It's main claim to fame is lower toxicity. There is a variation on this one that deserves looking into, especially for cars with big, powerful engines with radiators to small to provide good cooling, but application is valid in other situations too. This stuff has a very high boiling point, which means that smaller radiators, fans and aerodynamic openings can be used, conserving space, weight, and reducing wind resistance and horsepower loss to fans while boosting fuel economy. Rather than explain it, I'll just link you to a site that does.

Do check out these links, you will learn amazing things if you have a liquid cooled motor. In fact, you will understand things that you probably had no clue to, there's more to the cooling system than you think, and it is an area that just might improve your cars performance.

Lastly, there are the water wetters. These reduce the surface tension of the antifreeze/water mixture, allowing it to conduct heat better. Do they work? In a word, yes. They may not cure all your cooling problems, but the can add a margin of safety to a marginal system. One such product is Red Line, there are other similar products. This add expense to your coolant cost, but you can reduce the percentage of coolant, recovering most of the cost.