I know why it is discouraged to mix types of coolant. I can't think of any other explanation. I did a comlplete flush and cleaning 14 months ago. 1 month ago had to top off from some other repairs, yesterday upper hose split and temp guage was pegged, taped up hose to get home and wait for parts to come in. Expansion tank was filling but never returning to lower level. the hose from bottom of tank to rear of engine where there are a mixture of soft hoses and hard pipes. That larger hose was packed full of an oatmeal looking solid. I removed hose and even a hose on full blast wouldnt clear debris. Picked it out with screwdriver, flushed from all openings both directions. The most difficult part was threading the new lower radiator hose in the required maze to get ends to reach and be turned in right direction. I am sure it is easier by removing battery/tray air box but I did it without. Anyway, I wanted to give all of you a pat on the back while I was feeling good about my success, due in large part to the wealth of information supplied by this forum. Thank you.