Motoraid Heater Core replacement.
I had a terrible coolant leak under the wardrobe and rear dinnette(driver's side). I had replaced ALL rubber elbow hoses and even purchased a new "Y" steel pipe. I have the 1999 HD. Still had a bad leak. It was the heater core inside the heater box. I tried many avenues to locate a new core and even spoke with Rialta Heaven. They claimed they had never seen a failed one and were not interested in helping me. Luckily, I found the mfg. and P/N on the side of the heater box. It is an Evans Tempcon product. Winnebago Parts told me they no longer stock those and are not available. Eventually, I called the Evans Tempcon Co. and they seemed amused at all the trouble I had. They said theirs do fail at times but not often. Within 15 minutes my part was paid for and on its way. The core and pipe layout was exactly correct but I had to add some angle brackets to mount it to the existing box the way the old one had been. All works now and the water is hotter than ever and the cooling system works great; now that it holds proper pressure. I was very surprised that in the 6 months of research (coach was out of commission all this time!) that no one could help me......so I am writing this for future help.