The coolant res is a Ford Chassis part. Likely the same one for all 2007 and older Ford chassis. If you want a new one any Ford large truck dealer parts department can look it up and get it for you from the Chassis VIN. Or, you likely can find a used one at a salvage place that has pre 2008 Ford Chassis RVs.
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Randy - Manhattan, Kansas
2015 Vista 27N
2020 Ford Escape Hybrid