Welcome to the club, Leah. Our Monterey was only 6 months old when the same thing happened to our overflow coolant hose. The Harrisburg tech said the hose looked like it was off a much older coach, and it had several cracks in it. Luckily we were on I-5 already headed to Harrisburg for other issues when we lost coolant, and only had to be towed 10 miles or so; unluckily for the tow truck driver, it was a miserable rainy day. The Monaco tech thought somewhere along the line someone had scavenged our new hose to repair another rig, than replaced ours with one off an older coach somewhere. He said it not only looked old, but wasn't the best material for the use, and he replaced it with a custom fit higher quality hose he ordered locally; then he retrofit some of the other hoses because he didn't like where they were rubbing on things.
Joel