Hot Diesel Fuel

What is this thing under your T1N Mercedes Sprinter???

Well, it’s essentially a heat sink. The coil acts as that heat sink and cools the fuel returning to the tank from the high pressure pump as the fuel constantly circulates through the system and is on demand at the injectors.

The trouble is that the diesel pump operates at +25000psi and generate a lot of heat. The excess fuel is hot and need to be cool before return back to tank. Hot fuel has low viscosity so it can shorten the life of the pump. It only gets hotter when the tank is nearly empty, the fuel temperature will rise pretty dramatically and this fuel cooling really helps prevent the fuel from boiling.

It is found on all NAS aka NAFTA T1N OM647 2.7L (inline 5 cylinder) diesel engines on both the 2500 and 3500.

This contraption works fine, but you have to be careful if going off road. Only issue is the rusty Y connectors can start to leak fuel. Something to keep corrosion prevention on, some grease or fluid film type spray. Yours look pretty typical. It also helps if any mud gets up there for it to be repelled.