lower intake manifold gaskets, dexcool

Here is an email I received back from a very knowledgeable mechanic that I emailed about , dex-cool, the green stuff and lower intake manifolds

Hi Bill:

Ahh the eternal orange / green controversy. There is absolutely nothing wrong with Dex Cool but there is a lot wrong with the people who own the cars that it's in! When GM or any of the other manufacturers who use OAT coolants (that's nearly every make and model on the road these days) say the product should last five years or one hundred and fifty thousand miles that is not a guarantee that it will.

Apparently many people have lost the ability to open their hoods (lucky for me bad for them). Coolant in all modern cars should be checked monthly and I don't mean checked in the coolant recovery bottle but in the radiator. True, some cars do not have radiator caps but they also don't have a coolant recovery bottle --- they have a pressurized expansion tank. At least once every month with a truly cold engine the radiator cap should be removed and the quantity and quality of the coolant checked.

The coolant must touch the bottom of the radiator cap. If the coolant is low there is air in the system and that air must be purged and replaced with a fifty / fifty mix of coolant and distilled water. OAT coolants (under any brand name) do not get along well with air in a cooling system. Due to the very low natural pH of OAT products (that's what makes them work so well) they become highly corrosive when mixed with air. Air in the systems of cars with OAT coolants has been credited with about 98% of all cooling system corrosion damage.

So, can you use green stuff in place of an OAT product? Sure but you loose the long-life capability and you loose the added protection that comes from their low pH. Additionally OAT products typically do not have silicates or phosphates and the green stuff does.

There is a very specific reason for this. As it was discovered by the Europeans and later the Asian manufacturers silicates and phosphates damage soft metal and plastic parts. This happens because silicates and phosphates are abrasive not corrosive. These chemicals act like sandpaper as the coolant passes through the engine passages and ever so slowly abrade the soft metals and plastic. They are also spun out of solution by the high-speed shaft of the water pump often leading to early pump seal failure.

The real answer to the problem is to check the coolant monthly, check the pH every six months, and replace the radiator cap every two years or sooner if needed. The object is to make sure the pH doesn't drop below allowable limits (without regard to the time it has been in the system), there is never air in the system, and the coolant is NEVER allowed to remain in the system until it changes color.

We have several thousand cars we maintain here in the shop. And given proper preventive maintenance we see slightly fewer cooling system failures in OAT equipped cars than ethylene glycol systems. Actually when properly maintained we hardly ever find a failed GM intake manifold or intake manifold gasket. What we usually find on the problem cars is coolant that has been ignored for years. Today we had one that required cutting the radiator cap off due to corrosion --- that car also needs a ton of cooling system work.