This is the exact combo that I used a couple of weeks ago. I kept it simple. I drained and refilled. I didn't do any flushing. The coolant that came out was still bright yellow and clear. I replaced the thermostat as well and there was no signs of any corrosion there.

Enslow,

Thanks for the good information on PH. I have been using PH test strips for many years to evaluate the health of the coolant and when it needs to be changed. My thinking is that the long-life coolants of today are much better than they were when they were introduced. As long as the PH is above 8.0, I am thinking that the Ford long-life coolant is good up to the initial 6yr./105,000mi. and subsequent 3yr./45,000mi. scheduled change intervals. Your thoughts?

One question, Did you use coolant system cleaner after flushing the old coolant out?

No I did not use coolant system cleaner, because I was afraid of causing more problems. I have now flushed the coolant once more with a 1 gallon of concentrate and 1 gallon of distilled water...

Understanding pH in Coolants

Overview

The ideal pH (or pH at which a coolant is still effective) can depend on the type of coolant. Each type of coolant has a different inhibitor and buffer package which will affect the useful pH. A buffer controls the pH by using a balance of an acid and base. The acid pH = 0-7, the base pH is 7-12. (Actually, 7 is neutral, neither acidic nor basic.) As coolants break down, they produce a little acid which tries to make the pH drop below 7. The base part of the buffer takes the acid away protecting the cooling system from the acids. Once all the buffer is used up, there is no more buffer to control the pH, so the pH will rapidly drop below 7.

Buffer Packages in Two Common Coolants: Dexcool and G-05

In particular, Dexcool controls the pH using at least two different buffers: 2-ethylhexanoic acid/2-ethylhexanoate and sebacic acid/sebacate. The ideal pH for Dexcool is between 8.3-8.6 for a 30-50% mixture. (reference: http://www.acdelco.nichost.ru/files/antifreezedexcool.pdf ) A bottle of pH test strips may have a pH guide, but you cannot go by that guide because every inhibitor/buffer package has a different ideal pH. A bottle may say the coolant is good between pH 9-11. That information for Dexcool is misleading because Dexcool is designed to work at pH 8.5. In fact, if the buffer of Dexcool were to be used up, the pH would drop to below 7. Many coolants use 2-ethylhexanoic acid and are not called Dexcool. Most Prestone coolants have at least some 2-ethylhexanoic acid as the buffer.

Another coolant, G-05, uses a very different buffer system based on borate/boric acid. The borate buffers can maintain the pH anywhere from pH 7.4 to 9.2. Different makes of G-05 may use different proportions of borate buffer, but on average the ideal pH of a G-05 coolant is 8.0. (reference: http://msds.ashland.com/msds-ext/msdsDow...archHC&id=4 , http://www.valvoline.com/pdf/zerex_g05.pdf ).

Why Control pH?

In the times of the iron block, many eons ago, pH was kept quite basic using silicate buffers (the old green coolant). With the switch to aluminum intake manifolds, and even aluminum blocks, there was a need to control the pH around 8.0 or so (not so strongly basic). In fact, as long as your coolant doesn't go below 7, the metals in the cooling system are fairly safe. In many high schools, the chemistry teacher would add some acid to magnesium or calcium metal. You should have seen the metal turn into a white powder and bubbles of hydrogen escape from the experiment. Aluminum and iron, while not nearly so reactive, still react with acids (pH 0-7). The reason they set the target range of 8.0 for modern coolants is the pH is like a slippery slope. The basic portions of the buffers maintain the pH around 8.0 - 9.0 or so. Once the buffer gets used up as the coolant ages, the pH drops rapidly below 8.0 and goes acidic very quickly. If you measure a pH higher than 7.0, it will almost probably be 8.0 and above. You probably won't even measure any pH 7.0 because it will have already dropped below 7.0.

The buffers protect the metals from acids. The acids come from the reaction of glycols and oxygen to produce various acids. This cannot be prevented. ( https://dow-answer.custhelp.com/app/answers/detail/a_id/5280/~/lttf---thermal-degradation-products-of-eg-and-pg ). The basic part of the buffer system will react with the acids, effectively removing the acids from the cooling system. The chemicals are still there, but not in acid form.

Cooling System Washes

If you chose to use a cooling system flush, they often use an acid to clean up old oxides in the cooling system. Metal oxides in the cooling system can be stuck to the metal surfaces (rust). The acid wash will turn the oxides into a salt which will not stick to the metal surfaces.

If you do not flush out the acid wash properly, you will have two problems. The first is that you will have metallic salts in your coolant which could be potentially abrasive if not removed. Secondly, some of the acids wash will remain in the cooling system and consume the buffer of your new coolant right away. Removing the flushing chemicals is quite difficult and time consuming. I tried the CAT cooling system flush and my coolant really did come out BLACK! Draining and refilling only clears out about 50% of the water in the system. Each fill and drain will simply dilute the flushing chemicals 50% each time: 1st flush is 50%; 2nd is 25%; 3rd is 12.5%; 4th is 6.13%; 5th is 3.06%; 7th is 1.5%; 8th is 0.75%; 9th is 0.38%; 10th is 0.19%. Most buffers make up less than 10% of the pure coolant, so by the time you get your 50:50 mix in the system, your buffer less than 5%. Even after 7 flushes, you still have 1.5% of the old coolant in the system which can significantly reduce the life of your new coolant. In fact, it may be useful to use some pH test strips to ensure the pH of the flushing water is close to 7. After the CAT wash, it took about 8 fill/flush cycles before the flushings were nearly colourless.

NOTE: this method of fill/flush requires that the engine be run for about 1 minute between each fill/flush. This is the ONLY way you will get the lower block flushed out. If the engine is not run between fill/flushes, when you add your coolant in the end, it will turn muddy almost immediately.

Every fill/flush requires the addition of about 2 gallons. 10 fill/flushes would then require at least 20 gallons of fresh water to get the old flushings down to an insignificant percent. So, Stalag was not joking when he said it requires over 20 gallons of distilled water to flush. [i][/i]

This step is not optional and must be done. If you choose to ignore this simple diagnostic step, you will be like me and replace your heater core a second time. Buy a digital volt meter from harbor freight or wherever. Place the red lead into the coolant, and the black lead on the negative battery term. Set meter to DC volts. Make sure the range is et to show 0.000 and not just 0.0

If you reading is higher then 0.300 volts DC then flushing is required and not optional. Use motorcraft VC-1 flush. You will need to drive 100 miles for it to clean. Todays flush chemicals are weak for safety and environmental concerns.

If your reading is very high like in 0.500 thru 0.700 you will need to use 2 bottles of flush at the same time for 100 ~ 200 miles, and replace EVERY hose. You cannot clean the rubber hoses at all. No chemical, no brushed, no nothing. They have to be replaced.