I offer the following procedure I just developed as it seemed to work quite well. If someone else has more experience and knowledge, please chime in if your information can be beneficial to us all.
First of all, when you drain the C5's radiator, like most other cars I've owned, you only get out about half the coolant system's capacity according to the owner's manual. The rest must be in the engine, heater core, hoses etc., and it really makes sense to get all the old coolant out so you don't end up with a 50-50 mixture of new coolant and old. Having used the old Prestone Tee on other cars, it seemed to do its job of flushing out all the old coolant with the only drawback of being a little ugly. Looking at the C5's cooling system, there is already a Tee at the bottom outlet of the coolant recovery tank, which is pressurized. This will allow flushing the system through the coolant tank. To use this with pressure, I made a very simple and inexpensive adapter to connet to the top port of the tank. Simply buy 6" of 2" dia. radiator hose, 2-
2 1/2" dia. hose clamps, and some PVC fittings to adapt to a garden water hose. The O.D. of a PVC end cap for 1 3/4" pvc pipe fits nicely inside the 2"
radiator hose. The hardest part is fitting an adapter to this cap, which was drilled to except a pvc 3/4" adapter for threads. A little pvc cement holds it together. For some reason the male thread for 3/4" pvc will screw into the female thread of a garden hose, but the hose male end wont go into the female 3/4" pvc threads. Pvc male and female work OK. So I simply finished my adapter with a male thread and used a washing machine hose, which is female on both ends to connect with the garden hose.
This adapter is easily slipped onto the male threads of the coolant tank and held there with the hose clamp. After the petcock is opened and the radiator drained, the hose is turned on until the fluid comming out the drain becomes clear. Not knowing what the internal flow of the cooling system is, I closed the petcock and idled the engine until temperature exceeded the thermostat's opening point. With the engine still running, the petcock was reopened and the hose turned on until the drain water turned cool.
Now, I should have the coolant system filled with city water. To remove this, I removed the pvc fittings from the top of the adapter and poured 4 gallons of distilled water through the system, hoping it would push out the city water.
(At the very least, it should dilute it some.) Once the petcock finishes draining,
half the coolant system should contain fresh, distilled water. Close the petcock and pour 13.6/2 quarts (approx. 7 quarts) of Dexcool into the resevoir, most of which will go into the radiator. Tighten the cap and run the engine; after a few short trips, the water and Dexcool should mix giving the desired 50-50% mixture. You can see the coolant level in the tank, so if gets low, you need to add a 50-50 mixture now to bring it up to the proper level.
Whatdoyathink? :cheers:

 

I think you need to come perfect your system (with pics) on my car. :D



[Modified by Umrswimr, 1:27 PM 6/4/2003]

 

At first blush, my only concern would be if you didn't get all of the "city water" out of the system. Of what impact might that be? I know years ago no one thought twice about this, but maybe with today's engines, perhaps it is different?

 

Are there any block plugs to remove on the engine?

 

Wouldnt it be better to use distilled water??????????

 

If you carefully read his post, he added distilled water after he used the "city water" to flush the old coolant from the cooling system. The only question is whether this flushed all the "city water".

 

Regarding the quality of city water in your engine block, especially with an aluminum block, the only way to know for sure would be from experience. If such a person has this knowledge and experience, he probably works in the automotive industry and has test results along with visual observations from disecting engines and radiators. IMO, chlorine found in various concentrations in water from different cities could be the major culprit in causing internal coolant passage corrosion. Unfortunately, I am not a chemist so I dare not offer any further opinions other than the concentration level of chlorine or any other element in would most likely have an bearing on whether significant corrosion occurs. So, if you can't be sure you've purged all the city water, you've still benefitted by by diluting it. I just look at this situation as being, "If a little effort now can possibly prevent a major problem later on, then do it." Since my "distilled" water is actually condensed water from an airconditioneer or dehumidifier, it really doesn't cost anything. I do visually inspect the H2O for dust particles and either throw away the jug or filter the water. On the other hand, maybe the new Dexcool has additives that neutralize all the harmfull elements that are commonly found in city water. I wonder where the water in the orignal Bowling Green factory coolant mix comes from? :cheers:

 

DO IT THE EASY WAY FOLKS...
Replace what drains from the radiator every year or 15K miles. Use 50/50 with distilled water. 'Old' coolant is still pretty fresh, and negates the need for a complicated (and questionable) flush. You can adjust the time/mileage above to fit your personal mileage and desires. Bottom line is it costs around $5, takes little time to do, and you don't compromise your system with 'city' water.
I do the same thing on the transmission, so I don't have to flush the converter.

Take care.

JC

 

Having a reverse osmosis filtration system, I would not recommend using distilled water on your engine. R-O water is just a step down from the purity of distilled water, and you need to use PVC and stainless steel piping for it, as it will dissolve the metal from the pipes otherwise. Tap water is generally pretty balanced with things such as calcium, so it is not so harsh on metals.

Disclaimer: I am not an expert on this by any stretch of the imagination, but if the manufacturer demanded extreme purity of the water used in the coolant, one would think they would have put "distilled water" rather than "clean tap water" on the mixing instructions. Just my two cents, y'all! :cheers:

imp.

 

Interesting. But why would Reverse Osmosis water eat up aluminum...or any metal for that matter?? :confused: :confused: :confused:

 

I'm not entirely sure of the chemical reason for it, but water likes to have things dissolved in it (like calcium, iron, copper, etc)... probably why it is called the universal solvent I guess. Reverse osmosis and distilled water have almost all of the impurities removed from it, and so it tries extra hard to dissolve things back into it. When I had the R-O system installed, I asked about the plastic piping and stainless steel tap they were putting in, and the installer just said that if he used anything other than stainless he would be back in a year to replace the pipes because the water would dissolve them away.

imp.