Fumes in cabin 1.9TDI

[Al3x147]

Hi, my dad has recently bought a 1988 multi van which has a 1.9TDI engine conversion (AFN from a Passat). When the heater in the cabin is on and you are on the motorway there is a really strong smell of exhaust fumes inside. We have checked the exhaust and engine cover but there doesn't seem to be anything obvious anywhere. How could fumes be getting into the heater system? Any advice of things to check greatly appreciated.

[Aidan]

If it's exhaust smell then check the Tailgate seal as well as the engine lid seal ?
Or is it a smell of coolant that phosphate metallic taste smell in which case it could be the heater matrix leaking; I guess if you have a head gasket leak into the coolant and a heater matrix leak then I guess products of combustion could be escaping into the cab via the heater, is it using water ? is there signs of leakage below the heater under the carpet or rubber mat ?

all this assumes the exhaust is normal down the side of the engine J pipe to back box and exit rear right, if the exhuast has been routed forward from the engine before going backwards then maybe sliding door seal is the issue

[Al3x147]

Thanks for the reply, the tailgate was loose which meant the seal around the edge was probably letting in the fumes. A much easier fix than I thought! Thanks