Since I have an liquid to air intercooler and the engine and transmission oil coolers are watercooled also, I needed an large cooler in front of the van and I thought that instead of mounting it in front of the radiator and adding more heat to the engine radiator, I could mount it in the luggage rack on top of the roof.
I never carry anything up there anyway and it is out of the way, so I cut two luggage racks up so that I could extend it about six inches and create a air scoop. (just like the early vans have)
I ran two 3/4" lines from the intercooler and oil coolers up though the tray and out through the roof to a VW Jetta radiator, an electric waterpump circulates the cooling fluid and pumps when the diesel engine runs.
A screen keeps the crows out and the over hang also keeps the sun out of my eyes.