Dear Ole Mechanic;

I got a couple of antifreeze questions.  I did like you been talkin’ about an read my owners manual an it says to change the coolant every 24,000 miles or 2 years.  I haven’t changed it since the radiator hose blew.  When it blew the weather was warm enough that I put water in it an it worked fine.  When winter came I put most of a gallon of antifreeze in it an it never froze up.  Why should I put a half antifreeze  an half water mix in it?  That antifreeze stuff is a lot more expensive than water!

Cheap an Not Froze


Dear Not Froze;Antifreeze

I will tell you right up front that other than some expensive special chemicals that the racing folks use, water is the best heat-transfer liquid available. 

The problem is that antifreeze contains a lot more than just antifreeze.  If you do decide to use water or less than the 50-50 mix recommended, then do not forget to put a water pump lubricant and a corrosion inhibiter in also.  You see the water pump has a special seal in it that prevents coolant from running into or out through the water pump shaft bearing and ruining the bearing.  The seal is what needs lubricant, as the seal is between the stationary pump housing and rotating pump shaft.  By the way, the fan is usually attached to the water pump shaft on most pickups and rear wheel drive cars.  Should the seal let go, the bearing fail and the fan come loose, the fan may damage the radiator, cut radiator hoses, break automatic transmission cooler lines, punch a hole in the battery, put dents in the hood or all of the above.  I know because I have had to repair a mess like that in a customers truck while I was in my wrench swinging days, and it was not cheap.

Now, the corrosion inhibitor is needed because water tends to corrode metal, especially if it gets hot, then cold, then hot like an engine does in a car or truck.  I have not used the word rust, because aluminum does not rust--it corrodes--and there is more and more aluminum being used in engines.  Of course, iron is still used and when it corrodes, it is called rust.  The problem is that rust and aluminum corrosion do not transfer heat as well as the original metal did.  Too much corrosion and some parts of the engine will run hot, but it will not show on the temperature gauge because the excess heat does not transfer to the coolant.  So don’t forget to add an iron and aluminum corrosion inhibiter to water or a weaker than normal antifreeze mix.  Of course, all of this stuff in the right amounts is already in antifreeze.

Speaking of heat, there is another unusual benefit to antifreeze.  When the ethylene or propylene glycol base in most antifreeze is mixed with water, the solution has both a lower freezing temperature and a higher boiling temperature as well.  In other words, a 50-50 mix of antifreeze and water helps keep the engine from freezing and cracking, helps keep it from boiling over, lubricates the water pump seal and keeps corrosion down.  I suspect that antifreeze is starting to sound pretty inexpensive at this point.

One other thing that I have got to mention is the radiator pressure cap.  If you put a liquid like coolant under pressure, the boiling point goes up about 3 degrees F (Fahrenheit) for each pound of pressure.  A thirteen-pound radiator cap will up the boiling point of water to about 250 degrees and a antifreeze water mix to over 260 degrees.  That helps you to keep the radiator from boiling dry in summer heat when you want to turn the air conditioner on.

I have not mentioned the new orangeish-red colored extended service antifreeze because it does not apply to you.  I can tell by the two-year or 24,000 mile service interval you mentioned.  The change period for the new coolant is five years or 50,000 miles UNLESS it gets mixed with the older glycol-based antifreeze.  If you add the old style stuff to the new orangeish red antifreeze, then the change period should be two years or 24,000 miles.  Also, you cannot flush the older stuff out of an engine, as traces of glycol that you cannot get out will contaminate the new stuff.  Oh, and if you think the old antifreeze is expensive, try pricing the new stuff.  I believe it is sold under the trademark name Dexcool .

Why change coolant?  Because the water pump lube and corrosion inhibitors wear out.  Whatever you do, DO NOT run 100 percent antifreeze, as it does not transfer heat very well at all--at least not until it is mixed 50-50 with water.

Can you run water?  Sure just don't forget the additives or to drain it out of the engine block at night before a hard freeze.  By the way, the additives will cost you almost as much if not more than what antifreeze costs.

Herr Professor Nuzanbolts