Hello,
I noticed my coolant overflow bottle was very dirty looking. I took a sample of the coolant from the radiator and saw it was a brown/green color. After draining/flushing with just water half a dozen times, the water was still coming out with a brownish tint to it. I saved the last bucket of rinse water I drained and let it settle out overnight. There was a handful of brown silt-like substance in the bottom of the bucket. It was VERY fine in texture, like talc except tan/brown in color.
I ran some through a coffee filter and let it dry. It was as described above, like tan/brown talc.
I'm wondering what it was. It has been there since I bought the truck used from the dealer in Dec. 2005. Do you think it is some kind of stop leak? What's your guess?
Thanks

 

This is possible! What you can do is remove your thermostat then replace the housing, remove the upper radiator hose from the radiator and run the end of the water hose at the end of it. Start the engine and turn your heater on high fan with the temp to the highest heat setting. as the engine is running the water pump will circulate the water unrestricted throughout the block, pump, and heater core then back through the radiator. Naturally the water will flow out and you can check it as it does until it is clearer than you had it. If you want you could try disconnecting the lower hose from the radiator as well this way the water could drain out the bottom. When you get it to where you can live with it. let the remaining water drain out. Reinstall the radiator hose(s) and thermostat, then fill the system with the normal coolant mix adding a conditioner. Restart the engine keeping the heater on and leaving the radiator cap off until the system "burps". Once you see the coolant start to rise in the radiator neck then put the cap on and you are done. Make sure your over flow bottle is filled to the correct level. Check for any leaks and make sure the coolant level is correct.

 

its rust

 

tap water residue (minerals). chemical break down of coolant. oxidation of aluminum and steel parts. metal changes properties at high temps submerged in water and coolant for hours on end.

DO NOT SMOKE THE RESIN!!!

 

It seems that bajafun was the closest. I sent this question to Prestone.This was their official reply:

"Thanks very much for your inquiry. The debris that you are describing
may be what the industry refers to as transport deposition. Transport
deposition typically consists of corrosion particles, worn out
inhibitors, core sands (from the manufacturing process) and other
particulate from the cooling system components. These particles tend to
collect in the coolest part of the cooling system, namely radiator and
heater core."