Taking the Hype out of Anti-Freeze Fears

By Brian Klaubert

As seen in the December 2004 edition of the Neighborhood News

A recent television consumer report has raised considerable concern locally about GM’s DexCool anti-freeze. We have received a surprising number of inquiries from people who are concerned about their cars. I would like to share our experience with it to allow you to make an informed decision.

In 1995 GM introduced an anti-freeze that was intended to last 100,000 miles before it needed to be changed. It was a well-intended attempt to reduce maintenance costs for GM vehicle owners. The anti-freeze was called DexCool, and was introduced with an orange color instead of the traditional green color.

All automotive anti-freeze is based upon ethylene glycol, whether it is green, orange, red, or blue. Traditional green anti-freeze has borate, phosphate, and silicate. Any other colored anti-freeze is “free” of those chemicals. There are debatable environmental benefits and technical benefits to not having those chemicals in anti-freeze. But at this point many auto manufacturers have also switched to the same coolant formulation as DexCool. This includes Toyota/Lexus, Honda/Acura, Volkswagen, Volvo, and many models of Ford and Chrysler.

If your radiator cap, or owner’s manual, says use “Extended Life” or “Long Life” coolant, your vehicle is using the same chemistry coolant as the GM DexCool coolant.

So what has caused the fuss? Many GM vehicles develop a problem with clogged radiators, heaters that only blow cold air, and generally gummed up coolant systems. Concurrently, most 90’s era GM vehicles with V6 or V8 engines eventually wind up with a leaking intake manifold gasket. So which came first, the chicken or the egg?

The initial assessment of the repair community was that DexCool caused the GM gasket problem and radiator/heater core problems. It has become more apparent that poor intake gasket design has caused a DexCool problem. Many vehicle makes use the same coolant, but only GM vehicles develop the problem.

The GM intake manifold gasket is made mostly of a brittle plastic. Over the course of 40,000 to 70,000 miles, this plastic cracks at the points of greatest pressure. A slow weeping leak of coolant begins and progresses over the course of many months to being a steady leak of coolant. When coolant leaks out, air leaks in. Unfortunately, the extended life coolant, or DexCool, begins to form gel “globs” when it is exposed to air. It also forms hard crystals. The gel globs and hard crystals accumulate throughout the cooling system, including in the radiator, heater core and water pump.

The following GM engines are prone to the intake manifold gasket problem: the 3.1 liter and 3.4 liter V6 engines, and the 5.0 liter and 5.7 liter V8 engines. The new generation GM engines (2.8, 3.5, 4.8, 5.3, and 6.0) are not prone to this problem, nor was the old 3.8 liter V6.

On all vehicles using extended life anti-freeze, GM or import, it is in your own best interests to follow the following coolant flush sequence. You can wait until 50,000 miles for the first flush and then every 30,000 miles thereafter. On all vehicles, but especially 1996-2002 GM vehicles, check your coolant level regularly and do not let the coolant level get low.

I would not rush out and replace my orange coolant with green. If I had a leaking intake manifold gasket I would have it repaired promptly. You can replace your DexCool coolant with green coolant. It won’t do any harm. It is just generally better to stay with the fluids that the manufacturer recommended.

Brian Klaubert owns Christian Brothers Automotive – Hamilton Mill on Braselton Hwy in Dacula. They are the 2004 winner of Gwinnett’s Choice for Best Auto Mechanic.