You didn't mention what year your Journey is, but a clogged radiator sometimes occured on pre-02 Freightliner chassis motorhomes due to the engine blowby tube allowing crankcase blowby (containing oil mist) to be pushed through the radiator by the cooling fan. On '02 and later year units, the blowby tube was exteneded to end underneath the radiator so gas air from it doesn't go through the radiator. On our Journey, the tube ends right behind the hitch cross tube.
If your unit doesn't have the extended tube, you might be able to contact Freightliner to see if they'll extend it for you, or possibly supply the tube to do it yourself.
If your unit already has the extended tube, then just be sure to perform a annual cleaning on your radiator. You'll always have some residue build up on the radiator, and if you think about it, with the radiator in the rear, it doesn't get the "cleaning" the front radiator units get everytime they're driven in the rain.
Joe & Shelly, Justin, Tyler, Alyssa | Butler PA
2008 Tiffin Allegro Bus 43QRP|Cummins 425|Honda CRV