[rickj]

Hmmmmmm.   Not blaming anyone just asking  questions. Corrosion at bottom could mean a corrosive liquid is pooling at the bottom. Are you cleaning the radiator with anything like simple green? Are you using commercial truck washes to clean the coach? Have you driven on any salted roads?

Again not blaming anyone just trying to understand causal factors.

thank you for your response. good questions; do not use commercial truck car washes, do not drive in cold areas and salted roads, just gently power wash radiator occasionally. I believe you are correct that corrosive liquid is pooling at bottom, or that the coolant is suspect. however I check my pH and it is right at 8.0 and I change the coolant filter once a year. I also suspect the manufacturer, Atlas, as a possible manufacturing defect. Have to solve the problem as cannot keep replacing radiator every 24 to 30 months.