DexCool?

My truck ('01 GMC) needs a cooling system flush & fill. I can't tell if the current coolant is DexCool orange or regular green stuff - it's nasty brown. Is there any special procedure to flush the system, to avoid any potential contamination depending on what flavor coolant I put back in? Or, can I just flush it and refill with whatever is on sale?

That mud IS DexCool. I don't know the absolute correct procedure, but get rid of that crap. Green stuff is your new best friend.

I think you need to do a thorough flush to get the dex out, or it will precipitate and inflict badness upon your engine.

Appleseed wrote: That mud IS DexCool. I don't know the absolute correct procedure, but get rid of that crap. Green stuff is your new best friend.

Yup. Deathcool. Scientifically formulated to congeal and cause engine damage in 50k miles or less.

I asked about DexCool when I bought my van 2-years ago, and while I received responses like those above, the majority of people said it's not the devil people make it out to be. Although your's is obviously in bad shape, so yeah I'd be tempted to flush it & fill it with the standard stuff too.

Flush it out, pop all the hoses off and go at it with a garden hose. Refill with "all makes all models" (any brand will do, it's all the same stuff) then drain and fill the radiator annually. Do not use "classic green" silicate coolant, it's old tech and does not play well with literally all other antifreeze on the market.

flush it well and fill it with one of the universal antifreezes. I know most people here use the hose method but on badly gummed up dexcool systems at work we tend to flush them twice so it takes 10 gallons of 50/50 mix

petegossett wrote: I asked about DexCool when I bought my van 2-years ago, and while I received responses like those above, the majority of people said it's not the devil people make it out to be. Although your's is obviously in bad shape, so yeah I'd be tempted to flush it & fill it with the standard stuff too.

It actually kinda is. It is pretty evil.

GM entered into a contract with Havoline (the makers of Dex) and they are required to use subterfuge to make everyone think it is wonderful, but a lot of actual testing has been done. Its evil stuff.

I went through three heater cores under a 3/36 warranty on my 96 Impala SS (and a subsequent warranty carpet replacement).

GM has now sued Havoline a few hundred times.

But, flush well, refill with a good coolant that will be OK with all the newer metals, and it never hurts to use a sacrificial zinc anode somewhere.

Drain the radiator, refill with water and radiator flush (found in parts store), run with heater on for a day. Drain again, fill with water, run for a day. Drain again, refill with 50% distilled water and 50% Yellow antifreeze (Extended Life non-DexCool, Ford/Chrysler G05) or the pet-friendly green (Propylene Glycol). Do NOT use classic green Ethylene Glycol under any circumstances. It's nearly as bad for most modern motors as DeathCool is.

I'll wait until the weekend. The temps get down to the teens/single digits, for the next few nights, and it'll be warmer Fri-Sun. Plus, I'll have more time, to work on it and drive it around - my home/work commute is only 2 miles.

so …. is GM still using DexCool ? (brandy new Sonic) should I drain/flush and refill already ?

Do your best to get it all out of the block. I'm not sure if those engines have provisions to drain the block but try to get as much out as you can since it's already brown.

wbjones wrote: so …. is GM still using DexCool ? (brandy new Sonic) should I drain/flush and refill already ?

Not sure if they're still using it. If you have it, the general consensus is yes, get rid of it.

GM made several decisions while the left hand wasn't consulting the right hand. In the mid 90s, one of their big boo-boos was using clay tablets with dexcool. Clay tablets are added to a cooling system to plug small leaks. It was $0.0004 worth of insurance and if it prevented a leak for 300 miles until a car was out of warranty, it was financially worth the investment. Clay tablets and dexcool were a bad mix. Usually things were fine until air was introduced into the system. In the Impala SS example I gave above, many of us noticed "the waterfall" in the dashboard. As time went by and small amounts of water evaporated out of the system, the surge tank got a little low. On acceleration, the pump drew water out of the tank faster than it returned allowing air to get sucked into the system. First thing down the line was the heater core. When our coolant got low, it sucked in air and sounded like a waterfall in the heater core. This turbulent mix of air and coolant was a deadly sign. What it did (skipping the chemistry part) was cause the silicates from the dissolved clay tablet to become reactant with the coolant and it allowed lower-flow parts of the system to jam up with junk. I lost heat at 8000 miles in my SS. When I pulled the heater hoses and back flushed it, I got a half gallon of orange, gloppy metamucil out of it. GM had already caught on to the problem and most dealers tried to sweep you out the door with excuses. Mine continued to plug up until it finally blocked and it was replaced under warranty. The second one corroded through and dumped coolant everywhere at about 18k. The third one corroded through and I complained loud enough to get carpet too.

You may have also heard about LT1s and how the water pump seals kept failing and dripping coolant on the distributor. The distributor got a bad rap, but it wasn't its fault. The water pumps got a bad rap, but it wasn't its fault. The sandy jello got into the packing around the seals of the pump and ate them up. Then it started dripping on the optispark.

At 28k, I did GM a favor and flushed it all out. It required quite a bit of time cleaning the metamucil out of the block drains before I could even drain it. The throttle body coolant passage was so jammed that I had to rod it out with a coat hanger and a wire bore brush from my gun cleaning kit. I had the radiator pressure flushed, but it was surprisingly clean.

Anyway... now at 136k miles I have had zero relapse of any issues, and I've only flushed twice. Both times the coolant came out green, pretty, and with zero issues.

I never followed the tech much on this specific thing, but remember the Vortec truck engines (96-99) that kept leaking coolant between the manifold and the head? Same junk. When you pull the intake, the rubber seals are coated with orange jello and eaten away.

I worked for about 2 years at a GM dealer. The service bulletins and tech bulletins that came across my desk about dexcool were constant. Almost weekly.

Nick_Comstock wrote: Do your best to get it all out of the block. I'm not sure if those engines have provisions to drain the block but try to get as much out as you can since it's already brown.

That is a very good point... if the coolant is brown, it doesn't matter what it was. You still need to flush the same amount; whether its to get rid of all the dexcool, or to get rid of all the brown stuff that used to be coolant.

I run dexcool and don't have issues. I flush it once a year and have never had it gum up. But I have seen many a car with nasty ass dexcool.

I would consider switching the vette but the block drain plug is not accessible with engine in the car so it would be a whore to get it switched over. I'll just keep running dexcool.

In reply to curtis73:

I spent a very large amount of time getting everything out of my SS when I noticed the "waterfall". My block drains were completely plugged too. I was always nervous that I didn't get it all out but never had any issues after the complete flush switching from the Dexcool.

wbjones wrote: so …. is GM still using DexCool ? (brandy new Sonic) should I drain/flush and refill already ?

Yes, GM still uses DexCool. As a matter of fact, Ford cars now use it, too. (Idiots)

In reply to Javelin:

I thought it was reformulated? Depending on your definitions, most of the coolant out there now is using the same basic chemistry as "dexcool"(organic acid), including all those long life all makes coolants.

It is the devil. If it's old or conaminated, it will turn to mud and block things.

Some fool put it in a Jeep I work on and it took 3 drain/flush/fill before I figured out that I needed help and then 3 drain/fill flush with vinegar in a 50/50 mix to rid it of Dexcool again.

Thanks for the chemistry lesson, Curtis!

Kenny_McCormic wrote: Flush it out, pop all the hoses off and go at it with a garden hose. Refill with "all makes all models" (any brand will do, it's all the same stuff) then drain and fill the radiator annually. Do not use "classic green" silicate coolant, it's old tech and does not play well with literally all other antifreeze on the market.

So are you saying the Prestone most people use is bad too?

The only thing that I have had any luck with for flushing and cleaning out a system that has been gunked up with this stuff is using CLR in it. After flushing the system with water until it runs clear (I like to use hot water from my house by hooking a hose to the washing machine) I Then mix up a strong solution of CLR (using the powdered stuff) and hot water and add a very small amount of Dawn dishwashing soap just to cut the surface tension. Add this to the system and top off with hot water while the motor is running. I run this up to temp and take the car for a drive (50-100 miles) of highway cruzing is the usually what I do. Then drain rinse and fill with water and take for another drive but only go 10-20 miles and drain again and flush in the driveway with more water let idle and or blip the throttle a couple times for 10-15 min and drain and add standard 50/50 mix of your prefer non Dex Cool stuff. I have had very good luck with this method. The CLR seems to get rid of all the crusty nasty Dex Cool gunk as well as hard water deposits and I have not had any issues with it reacting with anything.

However as always use at your own risk.

I had a 88 chevy g30. I put a new engine in it filled with dexcool and didnt touch it for 100,000 miles and when I did flush it, it looked like new. Go figure.

spitfirebill wrote:

Kenny_McCormic wrote: Flush it out, pop all the hoses off and go at it with a garden hose. Refill with "all makes all models" (any brand will do, it's all the same stuff) then drain and fill the radiator annually. Do not use "classic green" silicate coolant, it's old tech and does not play well with literally all other antifreeze on the market.

So are you saying the Prestone most people use is bad too?

Which Prestone? Classic/conventional green? Yeah, that stuff has no place in a modern cooling system.

Javelin wrote:

wbjones wrote: so …. is GM still using DexCool ? (brandy new Sonic) should I drain/flush and refill already ?

Yes, GM still uses DexCool. As a matter of fact, Ford cars now use it, too. (Idiots)

okkkkkk …. this is the first new car I've had in 15 yrs. it's also the first GM I've owned (other than my mid-60's 1/2 ton pu work truck)

with the water pump issues that the Sonic has, I'm betting that if I swapped out to "real" coolant, that I'd void my warranty and berkeleyed over when the water pump has to be replaced