Back in the 60"s I was going to drive our 2 or 3 year old Plymouth Valiant to Seattle one hot Summer day. I noticed that the temp gauge was kind of high while going across the flat area West of Moses Lake. But then my Mom and I crossed the Columbia River and climbed the approximately 10 mile Vantage Hill. The temp REALLY went up, and I decided we needed to run the heater to try to get some more cooling. So we roasted in the non-air conditioned car until we reached the rest area at the top. The Valiant was not boiling, and we did not lose any coolant. I had thought that the problem might be bugs in the radiator fins, but I found that there were only a few. So I decided there must be something else wrong. I knew enough not to open a hot radiator, so I poured some water over the radiator and then let it cool down for about an hour. When I finally opened the radiator, I found that the coolant was very orange and was about as thick as whole milk from a Jersey cow. I didn"t have any tools or anything along to try to fix the problem and was more than 150 miles from home. My Mom and I decided that we would continue on our trip to Seattle and would carefully monitor the temp. If it got too hot, we would run the heater full blast.
We climbed Snoqualmie Pass and the air got cooler, so we didn"t have any more real trouble and we arrived at my Sister"s apartment in Seattle.
The next morning I decided to try flushing out the crud in the radiator. I got a garden hose and opened the radiator drain valve. The "coolant" flowed slowly out of the valve and onto the parking lot. I started pouring water into the radiator and after a few minutes, the flow out the drain was nearly clear. I then filled it up and closed the valve. I started the engine and let it warm up to operating temperature. Then I let it cool down a bit and opened the drain valve again. The flow was still quite orange, but it was not nearly as viscous or thick. After I drained the radiator again and refilled it, I decided that I had done what I could and hoped the car would run OK.
One thing I had not thought about was the rust stain the procedure left on that apartment parking lot. I ended up scrubbing it with a brush and the garden hose, but some of that rusty trail remained. The manager was not pleased with the mess I made, but nothing really happened about the stain. I felt bad about it.
Our trip back to Spokane was uneventful and the temperature never got hotter than normal. My band-aid repair of flushing the system out and adding plain water worked! At home, I installed a drain valve in the block of the Slant 6 to replace the steel plug and a flushing tee in the heater hose and did a proper job of flushing the whole system. With new Prestone and an extra can of anti-rust, the car was ready for the coming Winter.
I would assume that the rusty, contaminated coolant I discovered at the Vantage rest area was the original coolant that came in the car when we bought it new. Obviously the antirust ingredients in the coolant had worn out or at least were not working any more and had not been for some time. I don"t remember ever opening the radiator before, as I was a pretty new driver at that time and didn"t know better. My Dad probably never checked the coolant either. At any rate, the system had rusted very badly, probably from the engine block. The situation didn"t seem to damage anything. We had that car for several years after that and never had a bit of trouble with it. I did check the coolant several times a year after that and do so on all of my machines. If I see any brown tint to coolant, I replace it right away.
I wish I had saved a sample of that thick, rusty coolant. It would have been interesting to have tested it to see what the PH was and also to see if it was still effective as an anti freeze. It also would have been nice to have been able to show my Dad how really bad the coolant had been.
I would drain out the brown coolant, flush the system and replace it with new, quality antifreeze. But from my experience, I would suggest being careful with the brown liquid, as it might stain whatever you pour it on. Good luck!