A few years ago my 1992 Ford Ranger's thermostat had a leak and prior to this I found that running my air conditioner was causing the engine temp to climb sitting in traffic. I went and bought the thermostat to put in the coming weekend as now I knew where I was loosing coolant from on the 4.0 engine. Arriving at work on Friday morning I checked my coolant level to find it was low so instead of checking the over flow bottle I took off the radiator cap at first break after it cooled down. Inside the radiator could be seen that thick mucky sludge mess that clogs up the cooling tubes. I needed a clean jug so I could add water to the system to get home forty miles away but all we had was an almost empty Jug of simple green. It had about a cup left in it so I filled it up with water and poured it in the radiator.
I drove home the forty miles and parked. Next morning I went to work on the truck, drained the coolant removed thermostat housing expecting the thermostat, housing and inside block there to be filthy. It wasn't and looked like brand new. I checked the thermostat and it was bad so I replaced it. When I took off the radiator cap and looked down inside the radiator was clean as well, no scale or mucky sludge. It too looked like a brand new unit inside.
Road testing with air conditioner running full blast in stop and go traffic the temperature gauge needle barely nudged up from the cold mark. It had not run this cool in years. I now had full cooling again after cleaning the radiator out with the Simple Green. That Ranger was sixteen years old when I sold it and had the original radiator in it with not one leak or repair ever.
After hearing me tell of my accidental discovery a co-worker ran some Simple Green in his radiator for the same amount of miles as I had. He was happy to tell me that it cleaned out his radiator gunk also. Others have asked me how I knew to do this and I tell them all the same, "It was pure accident, I needed some water and a clean jug, all we had was one of the Simple Green jugs with about a cup left in it."
