What do heater hoses have to do with a fuel leak? Is there a fuel heater in the 2.5? Even so, you can drop a match into a bowl of Diesel fuel and it won't burn, explode or do anything but put out the flame. I suppose under 200psi of atmostpheric pressure it would be a concern

Do you see a fuel leak? Your nose should find it quite easily.

Could it possibly be a heater core leak? No fire hazard but it's not good to inhale coolant for extended periods.

Check whether your car is subject to the timing chain recall and if it was done. There's also some discussion about resonance valves on these cars.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD