Dex Cool


I have a 1998 Lumina LTZ with the 3.8 V6 engine. I just had to replace intake/exhaust manifold gaskets and numous other parts. The culprit and cause of these problems was Dex Cool. I had the same problem in a previous Lumina with 3.1 V6. I have read about past class action suits and other internet complaints about Dex Cool. I just wondered what the Car Talk Nation thought and whether this problem was real or urban legend.


This is very real.

DexCool can turn acidic if air gets entrained in the cooling system for a long period of time. Everyone I know who owns a GM vehicle with DexCool in the cooling system has it changed over to either the green coolant or to one of the universal coolants as soon as the vehicle goes out of warranty.



for those of us not familiar with DexCool, from the internet:

Some cars are coming equipped from the factory with so called “extended-life” coolants. One of the more popular extended life coolants is Dex-cool.

The “recommended” service intervals of Dex-cool coolant is 5 years 100K miles and in some cases 150K miles. These extended service intervals have not proven to be any thing but trouble for the consumer. In some cars, the coolant tends to turn to a thick, gooey, sticky, muddy, gritty, orange corrosive gel that fouls the radiator, heater, plugs coolant passages in the intake manifold and heads, and many times starves the water pump, resulting in overheating, and leaking. Mounting evidence suggests that Dex-cool reacts with plastic sealing surfaces, allowing leakage at the intake manifold gaskets. The best thing to do without voiding any warranty, is to change your coolant every two years with the recommended coolant.


If DexCool is recommended (or “required” as it is in my owner’s manual) isn’t it best to continue to use it, but flush/change it every 1 or 2 years (like the excerpt posted by Bill recommends)?


How did Dexcool make exhaust manifold gaskets fail ?


I find that url quite humorous as it comes from a radiator shop. How coincidental.

Faulty rad caps causes the coolant to turn milky brown. Yeah, right.

As some of the regular posters here know I don’t (and never have) work for GM or the makers of Dexcool.

However, I know all about the problem that GM created themselves resulting in a North American (for the most part) major automotive headache that GM refused to pay for.

GM used a plastic type intake manifold gasket in most of the V8 and all V6 engines from 1996 to 2003.

In Feb/03 they finally released a revised gasket kit (with new bolts and Loc-Tite and new torque specs.

The original gasket bolts flattened out causing air leaks at the corners as the manifold started to move due to the slack in the bolts.

Now, as most know, air and Dexcool make for a very corrosive mix when joined with engine oil.

The internet is loaded with complaints from this, but it turned out we paid for the repairs as it was proven to be a hell of a job getting GM to pay SOME of the cost never mind all of it.

The IMG leaked in my 2000 Olds Silhouette 3.4L V6 too and had it replaced with the new gasket in '04 (one year after I bought it used).

Since that time, there has never been a leak or other problem concerning Dexcool.

As insurance, I replace the Dexcool every three years instead of the 5 GM calls for.


Yeah, Dexcool sucks. My 01 Impala had it’s intake manifold replaced, and the coolant was replaced with the normal green coolant.


That was a typo.


I have a 1997 Regal GS with the 3.8. Have 155,000 miles on it. Still use Dex Cool. Have had the system flushed twice. GM mechanic once told me not to worry about the stuff unless it started changing color. If it started looking different, change it ASAP. A good way to tell if the lower intake manifld gasket is leaking is to watch for coolant pooling around the injectors.


GM has very quietly changed the formula for Dexcool, about time.