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Thoughts on going back to Dex-Cool? (99 C3500)

GM Guy

GM Guy

Manual Trans. 2WD Enthusiast
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Hey all,

I have my 99 C3500 chassis cab 6.5L 5spd 2wd tore down right now for a good radiator fin straightening, and a water pump replacement, so I figured now would be a great time to convert to another coolant.

The previous owner put green antifreeze in place of the original dex cool. Relatively clean, so I think he flushed it.

We are pretty disciplined about using distilled water with the Dex, and have had decent luck with it in the gassers, so I was wondering everyones thoughts on using it.

Basically I want to convert to an extended life antifreeze that is readily available in most places, since this truck will be towing all over the west. So IMO that narrows it down to Dex-Cool, Fleet Charge, or maybe Cat Extended Life.

Price is also a factor, and my local GM dealer is the cheapest at 14.xx for genuine Dex-Cool (IIRC my discount is 15 percent for being a high volume customer)

Any input on the matter is appreciated,
Thanks!
 
I have no problems with it myself, you just have to be EXTRA careful about flushing the system out when switching. ANY traces of green mixed with DEX can be VERY bad.
 
Look at the Prestone Extended Life as well I just switched Patch over to that with Water Wetter Diesel due to a blown heater core. (3 years old.) The Green stuff just doesn't perform well enough with marginal replacement part quality. Your system is used to the green stuff down to the water pump seal. You are replacing that, but, every surface is coated with the green stuff additive. Patch doesn't have the closed cooling system DexSludge requires so it's off the table. The 'Compatible with everything' was the selling point with Prestone Extended Life. This is also with distilled water use.

Fixed or not I have seen enough engines fail from GM's gaskets with DexSludge to use it as a last resort only.
 
So its best to use dex-cool with systems that utilize a surge tank, rather than a traditional cap and overflow setup?

Prestone is a no-go around here, silicate dropout seems worse with it (jello in the t-stat housing)

What would be a recommended flush procedure? tap water till it runs clear, then use shop air to get as much tap water out (blow out the heater core, air nozzle down the t-stat housing, etc), then top off with distilled water, run it a while, then drop it, and then re-fill with Dex-cool?
 
I actually used dishwasher soap in the last one that was nasty I had to flush out. It worked surprisingly well to get teh sludge out from where they put green in with dexcool. I have yet to see dexcool turn to sludge if cared for properly. You MUST use distilled water with it, or deionized filtered water. DO NOT mix it with other anti-freezes, even the universal stuff, that seems to make it turn to sludge quicker than anything else. And yes, it works best in a closed cooling system that utilizes a degas bottle where it's contact with atmosphere is minimized. I have seen cars from 96 with the factory dexcool in it that still did not look that bad, but I have seen cars with it less than 2 years old where the cooling system was caked. It is not a bad coolant, but it does require some extra maintence to keep it good. Once green has been run though, I would probably stay away from dexcool. You could go to G-05 easily enough, and it is also an ELC.
 
GM Guy said:
So its best to use dex-cool with systems that utilize a surge tank, rather than a traditional cap and overflow setup?

Prestone is a no-go around here, silicate dropout seems worse with it (jello in the t-stat housing)

What would be a recommended flush procedure? tap water till it runs clear, then use shop air to get as much tap water out (blow out the heater core, air nozzle down the t-stat housing, etc), then top off with distilled water, run it a while, then drop it, and then re-fill with Dex-cool?
Click to expand...

Great now you tell me! :facepalm:
 
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I don't know. I have never really done much maintenance on the cooling systems just flush and fill when I am there doing other things.

The old green systems there were flush products to help remove deposits, scale, and corrosion??? Deposits, scale, and stuff might want to cling or hold on to traces of green coolant??? The flush products might also help break down and clean out old green coolant too ??? Then flush with plain water a couple of times.

Are there flush products for dex cool coolants ????

I run a salt terminator product through my raw water boat cooling system even for fresh water to clean out any sediment and corrosion build up. Its suppose to help the cast iron develop a bit of corrosion resistance. I wonder if that would help clean out old coolant OR if would leave trace amounts of stuff not compatible with dex cool?
 
Ferman works on saltwater boats frequently. Be interesting to see what he thinks. Here there are people I know that run a detergent like Simple Green mix through to flush at season end or at pull out.
 
GM Guy said:
So its best to use dex-cool with systems that utilize a surge tank, rather than a traditional cap and overflow setup?
Click to expand...

I THINK this.... I don't know but figure Oxygen and Sun light are about the most destructive things and deteriorate most things the worst. Stuff can't Oxidize without Oxygen can it (most corrosion is a form of Oxidation isn't it)? In my mind a sealed system with minimal air exchange is better.
 
im a little old school on this. Flushing with the 1 gallon of flush designed to do it, rinse with water fron the garden hose and run green antifreeze. In having to use testing on semis that break a million miles it made sense to go for 100,000 mile coolant. In a truck that takes forever to get to 100,000 miles it not worth it imo. We had pickups inour fleet that would hit 100,000 in 1 year. Still wasnt worth it. We tested the green vs the long life, and it didnt even last twice as long.

Test strip the green, and if need at about 75,000 miles drain 1 gallon and replace it only and your numbers come out fine. Too many details and reoccurring problems with elc. Add the cost of distilled water to your elc, and the higher price, it does not save you any money. It is more expensive.

My 2c, not wanting to stir the pot.
 
So the G-05 chemistry is similar to regular green, so they mix relatively well? The dex chemistry is completely different then?
 
The high mileage AF's are Organic Acid in technology and will have behave in manner the same as Dexcool, sludging when mixing with green etc.

In the marine field I steer clear of the Organic Acid's they are corrosive to coppers, brasses and solders etc and hence shorten heat exchanger lifespans. For our vehicles though with Aluminium Rads not a concern. However over the years and before the Organic Acids came out the large coolant volume field was well used to adding additives to regular green to keep it up known as SCA's (supplementary coolant additives) the system works well though some would say that the whole test stripping etc is a chore. I now use Cummins DCA4 additive a chemically well developed additive and it can outlast high mileage which you still have to change out at some point. So you could just go Green and after a couple of years get a test strip or 2 and a bottle of DCA4 and treat accordingly.

Cheers
Nobby
 
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G-05 is Hybrid it's a mix of Inorganic and Organic technology. Personally I have never tried mixing it with green and really have no desire to find out.
 
nobby said:
G-05 is Hybrid it's a mix of Inorganic and Organic technology. Personally I have never tried mixing it with green and really have no desire to find out.
Click to expand...
G-05 is what FORD and CHRYSLER opted for. CHRYSLER went with it because it could blend with green without the issues that DEX was having. The downside to G-05 is it doesn't cool as well. I ran G-05 in a car with a new radiator, water pump, hoses, boiledo ut block and heads, new intake, ALL of it was like new. But it would overheat at idle in traffic(64 VETTE with a 11:1 comp, headers, cam all of that). Switched back to ZEREX green and it woudl get hot, but not overheating hot.
 
nobby said:
The high mileage AF's are Organic Acid in technology and will have behave in manner the same as Dexcool, sludging when mixing with green etc.

In the marine field I steer clear of the Organic Acid's they are corrosive to coppers, brasses and solders etc and hence shorten heat exchanger lifespans. For our vehicles though with Aluminium Rads not a concern. However over the years and before the Organic Acids came out the large coolant volume field was well used to adding additives to regular green to keep it up known as SCA's (supplementary coolant additives) the system works well though some would say that the whole test stripping etc is a chore. I now use Cummins DCA4 additive a chemically well developed additive and it can outlast high mileage which you still have to change out at some point. So you could just go Green and after a couple of years get a test strip or 2 and a bottle of DCA4 and treat accordingly.

Cheers
Nobby
Click to expand...

So the old school copper/brass/solder radiators should stick to the green?
 
http://content.valvoline.com/pdf/Zerex_DEX-COOL_AFC_Technical_Bulletin.pdf

Page 2 shows the corrosion test. Its near perfect for Aluminum and Iron and beats the spec for Copper, Solder, and Brass.

I have not had a problem with my dex cool system except the quick connect that deteriorated. I don't think it was because of dex cool.

I THINK the original release of Dex Cool did have some issues in some cars that gave it a bad reputation. I am not sure if it was some electrolysis, oxidation, or compound issue with some gaskets that was blamed on dex cool. Rumor or ? seems the original formulation was changed or some other change was incorporated????? but by '99 it was as good or better than green for protection IMO.

Having said that the green is not bad coolant it actually has a higher specific heat. Either will work in a '99 IMO and its really your preference.

I emailed CRC to ask if Salt Terminator would be a good flush for a closed system too and they did not recommend it for a closed system. I don't think they really understood what I was asking if it help clean out a closed system and help protect it for refill (not as an alternative to antifreeze coolant). Not sure if Enginkool is compatiable with dex cool.

Response...

"Salt Terminator is designed to be used in open coolant systems for boats and water recreational vehicles like Jet Skis to remove salt deposits. Salt Terminator is not an anti-freeze additive and would not be beneficial to a closed coolant system. It can be used to rinse off road salt residue from the under carriage and wheel wells. We would suggest a radiator flush for removing deposits from closed coolant systems in vehicles. There are additives like our Enginkool , part number 05348, that are designed for use with anti-freeze that assist in improving heat transfer in vehicle "
 
Seems like a good coolant for you with all the various equipment.

Says its compatible with most major brands of long life ethylene glycol but I would try my best to top off with same exact type AND brand on coolant these days.

I would print off a couple of copies of the tech paper while you have a link and put in glove box and service records of all equipment you use it in. Then if on the road you should be able to find a compatible top off at most large truck stops if the jug says top off is equivalent to the list on page 2 or the first paragraph "Cummins 14603, DDC, Terex, CatEC-1"
 
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