2001 Chevy Blazer 4.3L Vortec. About 106k miles.
Previous owner used plain tap water and Dexcool for god knows how many years in the cooling system, so my cooling system was heavily rusted when I bought it two years ago. I used to have overheating problems because of this. So, I flushed the cooling system with prestone radiator cleaner and distilled water literally more than 10 times about a year ago. Went through 12 gallons of distilled water. The coolant was pretty clean afterwards, so I thought I was good!
Then a year went by. The car drove great, and never had any overheating issues. I opened the radiator cap last week, just to check it out, and my coolant was looking like muddy water again. No sludge or chunks in it this time, it just looked like “brown coolant”, so I decided to remove ALL the rust in the cooling system. By the way, I have done pressure tests and coolant combustion gas tests etc to verify I don’t have any head gasket issues.
I flushed the cooling system with 8 gallons of distilled water, then poured Evaporust in the cooling system with some distilled water. Drove it with Evaporust for 3 days, then I drained the coolant yesterday. The Evaporust drain was nasty, the water was completely black.
After draining the Evaporust, I flushed the system with 10 gallons of distilled water, until clean water started coming out. I also removed all the hoses, and flushed the block, the heater core, and all the hoses with distilled water. Not even a little bit of tap water will ever go in my cooling system.
Then I filled the system with Prestone Max coolant. The coolant is still kind of dark looking, but it is green now.
So here’s the plan! I will from now on just drain the radiator and put in fresh coolant about every 4 months. The coolant should always stay clean if I do this. Rust is never a good thing, because rust particles will wear out water pumps and rubber seals overtime.
I want to keep the cooling system clean, because I absolutely do not want the heater core or the radiator to rust through and start leaking, and I plan on keeping the truck for a long time, because it’s got low miles for a 2001.