Ok,
Now that we've got the terminology straightened out, just exactly WHAT metal coolant hose/tube are you speaking of? We have an '04 Itasca Horizon 36GD with the CAT C-7 330HP and, I just changed out 99% of the heater and radiator hoses but, there were no METAL ones. The only metal involved in the coolant operation are my two "Motor Aid" elbows that are used in routing coolant to the water heater heat exchanger. Those were rusted when we purchased the coach, 7 years ago. So, I replaced them with Copper ones since I couldn't find the identical steel bent ones. But, which metal ones are you speaking of?
Scott
Scott and Karla SDFD RETIRED2004 Itasca Horizon, 36GD Slate Blue 330 CAT
2011 GMC Sierra 1500 Ext Cab 4x4 Toad
2008 Caliente Red LVL II GL 1800 Goldwing KI60ND