Dear Ole Mechanic;

I had my 2001 Jeep in for service the other day, and my mechanic asked if I had ever had my cooling system serviced. I had not, but I am the second owner and had no idea if the first owner had it serviced. The mechanic got a meter of some sort, stuck one wire down into the coolant and put the other wire on a metal part of the engine. He said there was “1 and Volts” and that I should have my cooling system serviced--which RadiatorI scheduled. What did he do and why is 1 and Volts bad? I thought myJeep had a 12 Volt battery. Can you explain what he did please?

Keeping It Nice

Dear Ms Nice;

Yes, your Jeep has a 12 Volt battery, but that was not what your mechanic was checking. First, a brief lesson about batteries. A battery has electrolyte that surrounds two sets of plates made of different metals. The reaction between the electrolyte and the metals causes an electrical difference called voltage. Producing that voltage causes the metals to change, and in some cases, erode the metals. A battery is made to be recharged so the erosion is reduced.

When antifreeze is new, it has inhibitors in it to keep it from being an electrolyte. As the antifreeze gets older the inhibitors wear out, and it can become an electrolyte. Due to the different metals that antifreeze comes in contact with in a cooling system--usually iron and aluminum--it can erode the metals. It also produces voltage as it does. Your mechanic was using a voltmeter to see if your antifreeze had become an electrolyte. It had. He put one voltmeter lead in your antifreeze and the other on some metal that the coolant comes in contact with. That could be either the engine or a metal part of the radiator. The rule is: If there is less than one volt, things are OK. If there is one volt or more, then the cooling system should be drained, flushed out and refilled with a 50-50 mix of water and new antifreeze.

Your mechanic did the right thing, as most manufactures now call for cooling system service every five years or 50,000 miles. Your Jeep is now almost seven years old. Since there was no way to tell if it had been serviced, the voltmeter was the easy way to test it. By the way, the hoses and fan belt are probably almost seven years old too. Don’t be surprised if your mechanic suggests that they be replaced along with the antifreeze mix. Better to be safe than stranded in the middle of NoWhere, Texas.

Herr Professor Nuzanbolts