Let me say,
We knowfrom test conducted by Prestone, conventional coolant (yes the old green stuff) has a life of 13 + years(at that mark they stopped the test) and it's contaminants that kill thecoolant and damage components. With thatsaid, IMHO,
1. Nothing substitutes a periodic flush of the radiator
2. When I drain the coolant, I place a doubled up paper towel over the funnelwhich filters to less than 3 microns (much better then any of the inlinefilters)- in terms of contaminants, the coolant is now as clean as when it cameout of the original bottle. Provided it meets all the other test I do, it isreinstalled in the vehicle.
3. I have installed a magnesium anode in all overflows (same electrolysisprotection used per code for all underground tanks)- Zinc anodes are availableas well (JC Whitney, etc.) specifically for automotive applications and sellfor about $12, they attract all the nasty stuff that destroys radiators, pumps,hoses etc and they become the sacrificial lamb- and keeps the ph of the fluidneutral. The inside of my cooling system and related components is spotless-literally!
4. I check the ph (using a swimming pool kit) - and check the alcohol contentusing a conventional coolant bulb type test device ($10 at any parts store)
the results.....
1. Contaminant production is eliminated by 90%+ as a result of the neutral phmaintenance
2. Contaminants that are produced are contained outside of the system flow, inthe overflow at the anode. At this point I have less contaminant in my systemthan if I used an inline filter because we have eliminated 90% of theproduction and contained the residual.
3. With the paper towel, I can actually see the residual system contaminants(which you can typically count) and by most accounts visually know if apotential problem exist by the type and color of the products. The coolant isas clean as if I had opened a fresh container.
4. The system is clean and performance level known.
My personal results...
My father (an ol salt flats racer & aerospace engineer) starting this inthe 1950's and typically the conventional coolant lasts 10-20 years in thevehicle before requiring replacement.
I cannot remember repairing a radiator or heat exchanger or water pump duringmy 50+ years on this earth on any of my family's vehicles- (I take that back, Ireplaced 2 water pumps on my 1990 F150 when due to a pulley tension/alignmentproblem it ate two bearings/seals, my fault as I didn't check it the 1st time,but at 80,000 miles I was not too surprised to see a leak from the water pumpbearing)...........I did replace the radiator on my wifes 1997 Cougar sport at the 17 year mark....the aluminum core was fine and spotless but, the plastic shell started to crack and was seeping....the coolant in my 65 mustang is approaching 20 years old........the system is spotless....the waterpump, new when I rebuilt the car 30 years ago!
We typically keep our vehicles for 10+ years. Our list of vehicles includes...
1959 221 CID V8 Ranchero (1965 to 1971)
1932 Flathead V8 Ford Coupe (1960 to present)
1965 Mustang (1965 to present)
1969 F100 (1972 to 1984)
1984 F150 (1984 to 2006) (400K+ miles w2 rebuilds)
1979 Honda (1982 to 1990)
1987 Toyota Celica GT (1987 to 1997)
1990 F150 (1990 to 2006)
1997 Cougar Sport (1990 to present)
2006 Mark LT (2006 to present)
2006 F150 4x4 (2006 to present)
IMHO, basic chemistry makesit real simple to keep things in good shape......and there is a very convenient drain located on the radiator precluding the need to "pull the hose"...although it's best to purchase a short section of 3/8" diameter hose (IIRR) to connect to the drain port so you can direct it into a bucket/pan/etc.
IMHO, drain it, flush it, filter it, test it, install an anode, and re-install the existing coolant.