Lucky, you made me wonder if they did in deed change the service manual after '99.

The '03 sservice manual actually calls for deionized water. That was a shock!

Draining and Filling Cooling System

Caution

With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the surge tank cap, while the cooling system is hot and under high pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders, and the person removing the cap. Serious bodily injury may result.

Important

If the procedure below is not followed a low or high coolant level condition and/or vehicle damage could result.

1. Park the vehicle on a level surface.
2. Remove the surge tank cap:
3. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
4. Place a drain pan under the drain ****.
5. Open the radiator drain ****.
6. Allow the cooling system to drain completely.
7. Inspect the engine coolant for the following:
* Discolored -- follow the flush procedure below.
* Normal in appearance -- continue with the next step.

Notice

When adding coolant, use DEX-COOL® coolant. If silicated coolant is added to the system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolant will require change sooner-at 50 000 km (30,000 mi) or 24 months.

Notice

Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
8. Close the radiator drain ****.
Tighten

Tighten the radiator drain **** to 2 N·m (18 lb in).
9. Fill the cooling system through the surge tank.
10. Fill the cooling system with a 50/50 mixture of DEX-COOL® coolant and deionized water.
11. Start the engine.
12. Allow the engine to idle for 1 minute.
13. Install surge tank cap.
14. Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant temperature reaches 99°C (210°F).
15. Shut off the engine.
16. Remove the surge tank cap.
17. Start the engine.
18. Allow the engine to Idle for 1 minute. Fill the surge tank to 12.7 mm (0.5 in) above the COLD FULL mark on the surge tank.
19. Install the surge tank cap.
20. Cycle the engine RPMs from idle to 3000 in 30 second intervals until the coolant reaches 99°C (210°F).
21. Shut off the engine.
22. Remove the surge tank cap.
23. Top off the coolant as necessary, 12.7 mm (0.5 in) above FULL COLD mark on the surge tank.
24. Rinse away any excess coolant from the engine and the engine compartment.
25. Inspect the concentration of the engine coolant.
26. Install the surge tank cap.

Sorry, guys, I know this doesn't make this controversy any clearer, I am just stating the facts!

 

UH.......Dude, if you use 50/50 you are already diluting your antifreeze by 50%. So are you saying you delute it even more with more water?

 

That's a good example of what goes on at GM and then wonder why the service techs don't know anything.

 

This is from that same No-Rosion question and answer article, but farther down the page. Even more confusion fodder.

Q. What type of water is best to use as coolant?

A. Many people have “heard” distilled/deionized water is best to use in a cooling system. This is WRONG. While it certainly is true that distilled water’s purity prevents electrolysis and scale/deposit formation, it unfortunately comes with a potentially very damaging side effect. During the distillation/deionization process, water is vaporized into it’s gaseous phase, so all impurities are left behind. These impurities include a number of minerals, including calcium and magnesium – the two components of “hardness.” The water is then condensed back into it’s liquid phase, so the resulting liquid is pure water – in fact, some of the purest water on earth. The problem is that when water is distilled, or “stripped” of impurities, the resulting solution is composed of chemically imbalanced “ions.” This leaves distilled water “electrochemically hungry,” so it will actually strip electrons from the metals in a cooling system as it attempts to chemically re-balance itself. As it chemically removes electrons from the cooling system metals, it does damage that will eventually lead to leaks and system failure. Using distilled/deionized water in combination with 50% antifreeze is fine, as the distilled/deionized water will seek and find electrochemical balance from the various chemical ingredients in the antifreeze mixture. However, distilled/deionized water should NEVER be used as straight coolant, no matter what additive is used. And rain water is NOT advised, as environmental pollutants can cause rainwater to be acidic in pH (i.e. "acid rain"), which will cause corrosion and various problems.

The best type of water to use as coolant is softened water – especially if you run straight water coolant, without antifreeze. During the water softening process, the same impurities and minerals are removed from water as the distillation process – but with one very important distinction. Rather than STRIPPING the impurities from water, softening EXCHANGES the impurities with a sodium ion. The resulting solution is electrochemically stable and ionically balanced, making softened water very stable, pure, and non-threatening to cooling system metals. It should be added, there seems to be a perceptual issue with regard to usage of softened water. Many mistakenly believe that because SALT is added to water softeners, softened water must contain salt, a substance known to be very corrosive. Nothing could be further from the truth. The salt that’s added to a water softener is NaCl, or sodium chloride. During the softening process, only the sodium ion is exchanged into the water, whereas chloride ions are removed when the softener is regenerated. Therefore, softened water does NOT contain corrosive salt.

So where can I buy me some "SOFT WATER"????? In Texas, when I lived there I could get that straight out of my house because I had a "Soft Water" system, I don't have that here in MD, so where can you buy Soft Water, or can you?

 

Have your house water tested by a lab...you might have "soft" water and not even know it.

 

Adding the antifreeze does not raise the boiling point of water. The radiator cap allowing the system to become pressurized is what increases the boiling point (higher pressure than atmospheric = higher boiling point). When you add any chemical to water (salt, sugar, etc.) it lowers the freezing point. The "bad thing" (at least for a cooling system) is that the boiling point is also lowered.

 

Wow! I could have sworn that my service manual for my 99 says tap water. I gotta check it again.

Thanks DIXZ

 

fixed it fer ya

 

The 2003 owners manual (see GMPARTSHOUSE for other year manuals) says a "50-50 mixture of clean, drinkable water and DEXCOOL".*
*found at 5-23 (252 of 370) on the pdf file.

 

Okay, so I'm not crazy. That's exactly what my service manual states as well.

 

Not sure where you are getting your info on this. I had to dig up my old college lab books on this one, and sure enough, we had tested the boiling/freezing point of water after antifreeze was added. The results:
The boiling point of water was increased 32.9 degrees F for every 76 grams of antifreeze added to 1000 grams of water, while the freezing point of water was decreased 35.3 degrees F for every 76 grams of antifreeze added to 1000 grams of water.

With regards to water under pressure...you are correct. Pressurizing water does increase the boiling point. For example: a closed system at 15 psi : water will not boil until it reaches ~248 degrees F.

 

[QUOTE=IrishJoker;1562553118]This is from that same No-Rosion question and answer article, but farther down the page. Even more confusion fodder.

Q. What type of water is best to use as coolant?


The best type of water to use as coolant is [B]softened water [/B

we have been using softened water for years, also using a reverse osmosis system for our drinking/cooking water. another plus is, that we don't get water spots on the car when we wash it. hard ( tap ) water will leave all those little spots.

 

From a chemical engineer and corvette nut: Deionized water in very,very pure form is very corrosive, but the addition of DexCool contaminates it enough to make the combination very stable. Since water is a better heat transfer agent than DexCool, I use a mixture of 40% DexCool and 60% Deionized water. This provides a more than adequate temperature range with improved heat transfer between the engine and the radiator.

 

Yikes, I've been running distilled/Water Wetter in my old Firebird with a Be-Cool aluminum radiator for a few years. Looks like it's time for a flush. Where do I buy soft water though??