1996 Riviera with regular 3800 Series II -- Dex Cool question

Hi all, I have just acquired an impeccably maintained 1996 Riviera with the normally-aspirated 3800 Series II engine. The car has 51,000 miles.

I notice the car has Dex Cool coolant in it, and, since I don't know how long the current coolant has been in the car, I will replace the coolant to be on the safe side.

I know that there is controversy regarding Dex Cool, but it appears that the key is maintaining the cooling system and replacing the coolant at regular intervals.

Any problems with continuing to use Dex Cool in my Riviera?

I look forward to participating here, and I'll post more information about the car when I've had an opportunity to shoot some photos.

Welcome! People say dexcool rots gaskets. When i pulled off my lower intake manifold gaskets, they were pretty gnarlyl. I flushed out my system and am now running the universal green stuff.

People say DONT MIX DEXCOOL AND THE UNIVERSAL STUFF! I did it before and nothing bad happened.

green stuff is cheaper than dexcool and has never been reported to rot gaskets. Just my two cents!

Sir Psycho, thanks so much for your reply. This is very helpful.

Hi Brian,

DexCool lasts 5 years, compared to 2 years with the green stuff. So if the car has Dex, there's a better chance the coolant is still good. Still, I'd have it flushed and replaced.

Contrary to what you may hear, Dexcool does not "rot gaskets". GM used an improper gasket material; there is a $35 replacement available. It's a gasket problem not a coolant problem.

Don't want to change the gaskets? You can swap to green, but then you'll be flushing every 2 years, and any damage already done to the gasket will not go away. It will probably not get any worse, but you're just buying time really.

Imo, the best solution is to change the gaskets and continue using Dexcool, flush every 5 years. The replacement gasket will last forever, and you can use the superior coolant.

Thanks, AA! I'll take your helpful comments into consideration, and will talk it over with my mechanic.

My understanding is that DexCool becomes more acidic as it ages (more than 5 years). I have taken to draining and refilling my radiator once a year, as opposed to 5 year full system flushes. I like to have an annual routine. I also added a drain plug to my transmission pan for the same purpose. Drain and fill the pan and radiator once a year. While I'm waiting for those things to drain I suck out the PS fluid reservoir and pour in new.

Like AA said - GM used the wrong combination of materials on the intake gaskets. DexCool got a bad rap because nobody changed it at 5 years like they were supposed to. 5 years/100K miles does not mean lifetime!

If you have a non-supercharged 3800 (which you do) the plastic upper intake manifold is subject to exhaust eroding the port around the EGR tube. Aftermarket supplies a metal repair sleeve for that. You may or may not run into that when you pull the UIM (upper intake manifold) off to get to the LIM gaskets (Lower Intake Manifold)

In my opinion, plastic should not be used in any primary engine part subject to fluids, oils, exhaust etc. (small things like timing chain tensioners and PCV valves okay...) Think about the disaster GM used to have with the nylon gears on camshafts - they would strip long before the chain would wear out! How much weight and money did they save, and headaches did they cause by using plastic instead of metal on the LIM gaskets and intake manifold? Wasn't worth it!

Anyway, now you know what to look for.

Derek, thanks for the additional information. Clearly, I've got a lot to learn about these cars!