Rick's Free Auto Repair Advice

Is DexCool bad

DexCool problems

Mechanics say they hate DexCool and blame it for all kinds of problems. Most aren’t the fault of DexCool.

Here’s the REAL scoop on Dex-Cool and coolants in general.


First some history

Most of the older green coolants were silicate based. Their primary job was to prevent freezing. But they also had additives to prevent corrosion. In the case of the green coolants, the silicates deposit on metal surfaces to “PASSIVATE” them. In other words, the silicate coats the metal parts to prevent electrolysis. The problem with silicate is that it’s abrasive, so it’s tough on water pump seals. Plus, green coolant doesn’t have a long life—-max 2-years or 24,000 miles. When car makers switched to aluminum engines and radiators and away from cast iron components, they also switched to long-life coolants. The old rule was that you could add the newer coolants to the old green stuff and all you did was reduce the life of the long-life coolant to that of the old green stuff. Well, history has proven that theory wrong. You CANNOT mix coolants at all (More on that later>

The Dex-Cool Lawsuit

So GM switch to organic acid technology (OAT) and named that orange coolant Dex-Cool. And, they gave it a 5-year, 100,000 mile lifespan. At the same time, GM also started using plastic intake manifold gaskets with a silicone bead around the ports. For some reason (and NO ONE agrees on why this happens) the gasket material and Dex-Cool interact with one another, causing leaks. The problem was so extensive that it affects just about every 3.1 and 3.4-liter made in the late ‘90’1 and early 2000’s. The repair involves pulling the intake manifold and replacing the gaskets with a re-designed style. At the time, many shop re-used the old intake manifold bolts with the new gaskets and then re-installed DexCool, only to see the gaskets fail again. So they blamed DexCool. Wrong!
The problem with these gaskets is that they’re fairly low torque (because they’re plastic). So if you don’t use new bolts and follow the torque directions TO THE LETTER, you’re going to get another leak.
Bottom line is that owners sued GM in a class action and won a settlement to reimburse them for the gasket failures.

So it’s true that DexCool caused gasket leaks, but the real problem was incompatibility between the plastic and the coolant. Everyone assumes the problem was Dex-Cool, when in fact, the problem was the type of gasket material combined with the use of Dex-Cool. GM has redesigned the gaskets that the problem has now been fixed. GM still uses Dex-Cool coolant and there is no longer a problem with gasket coolant interaction. So contrary to the ranting, DexCool IS the recommended coolant for GM engine.

Other DexCool problems

Shops reported other problems with DexCool engines besides the 3.1 and 3.4-liter engine. Specifically, shops reported sludge buildup, especially in cast iron engines. But after a thorough investigation, it turns out that the only time sludge builds up is if the engine is low on coolant. When engines run low on coolant, the organic acid technologies oxidize and cause iron oxide deposits. The “rusting” usually NOT affect newer aluminum engines. But, running ANY engine when it’s low on organic acid type coolant cause form sludge.


Enter the new coolants

After GM came out with Dex-Cool, ALL the car makers jumped onto the reformulation bandwagon. Honda came out with a blue low-silicate formula. Others adopted a Hybrid Organic Acid Technology (HOAT). And each company formulated their coolants to work with the types of metals, gaskets, and seals used in each particular engine. The current situation is that you cannot even use a single coolant for an entire manufacturer’s lineup. Ford has several different coolants and you must use the correct coolant in each engine, simply because every engine has a different combination of seals and plastic materials.


Universal coolant? Ba-humbug

The big name coolant manufacturers felt left out of this game and somebody had to make a coolant that could be sold at retail auto parts stores. So the big name brands came out with “universal coolants.” Yeah, guess what? There’s no such thing. I’m not aware of a single car maker that condones the use of a universal coolant in all of their models and engines.

Mixing coolants becomes a HUGE no-no

Remember I talked about the old theory that it was ok to mix coolants? Well, time has proven that theory wrong. Mixing different coolant formulas is a prescription for big time trouble. In fact, Gates (the belt and water pump manufacturer) recently issued a service bulletin warning auto repair shops that their water pump warranties are null and void if the shop uses the wrong coolant or mixes coolants. Gates has seen water pump failures in as short as 7 days, although most other failures won’t show up for a long time. But if you mix coolants, or use the wrong coolant an get a leak or clogged heater core down the road, who’s going to suspect it’s the fault of the coolant.

Bottom line

If someone tells you to use a coolant OTHER than the one recommended by the car maker, DON’T listen. If you have an extended warranty, you will void it. Even if you don’t, you risk major damage. Most engines take less than 2-gallons. Dealer coolant will cost an extra $10/gallon. Why risk engine, radiator, heater core, gasket, water pump, heater tubing, and seal failure to save a lousy $20?

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Learn how to check your coolant here

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat



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