Smelling Coolant and Overheating With No Visible Leaks on Lincoln Navigator

The Lincoln Navigator is known for displaying the normal symptoms of a coolant leak, including overheating, the strong smell of coolant from the engine, and illumination of the low engine coolant warning light, without any visual signs of coolant leakage.

This leak is difficult to locate as it is buried underneath the intake manifold, and only begins to leak coolant onto the ground in advanced stages of disrepair. This leak springs from the heater tube, which allows coolant to flow between the water pump and HVAC heater core.

When the connection for this tube begins to leak, the coolant burns on the hot engine, and produces a sweet smell that is unmistakably engine coolant.

The remedy can be complicated, and will necessitate removal of the intake manifold, heater tube, and possibly the water pump. After removal of these items, the connector may be replaced, or a set of o-rings, depending on the year of the vehicle.