There are two "walls" that the heater hose has to travel through before getting to the core. I believe the rubber hose from the engine turns and goes though the wall to the area where the wiper motor is and connects to a pipe that goes through the next wall to the inside of the car connecting to the core.

Raise the hood all the way and remove the black plastic leaf guard. The rubber hose terminates under the guard.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)