like the common blend door failure on the Expedition. The problem is
either with the heater core not getting hot, or the blend door not
diverting air through the core. This is a common problem that Fords have. It is caused by the blend door
getting stuck. This door is located behind the glove box and it
controls the flow of Heat and A/C. Its probably stuck or broken,
allowing the cold air from outside to come in instead of the heat from
the heater core.
The heater core is difficult to
change on the Ford trucks. They have it buried in the plenum box and
you have to remove the steering wheel, steering column, dash, evacuate
the refrigerant system, drain the radiator, and remove the plenum box to
get to the core.
Replacing the core is easy, getting to it is a day's
work. The Expedition is particularly difficult to get to. It is almost
above the transmission tunnel and well buried behind the dash. The
Expedition uses the same plenum box as the F150, so any information on
that system applies to the Expedition/Navigator.
need to be sure that the heater core is really the problem before
tackling this job. If you have a pool of coolant on the floor, you'll
have to go after the core. If the problem is lack of heat, there are
some things you need to eliminate before tearing into the truck. You
need to make sure that coolant is flowing through the core. Check the
temperature of the heater hoses going into the firewall when the engine
is cool and see if they warm up together as the engine warms up. If both
hoses get hot at about the same rate, this is a good indication that
coolant is flowing through the core. You can also remove the hoses and
flush the core with a water hose splice from Home Depot and a water
hose. Water should flow unobstructed through the core.
appears that coolant is flowing and you don't have obvious leaks, the
next step is to check the blend door. This door controls the air flow
through the heater core and failure is common on Ford trucks. When the
door breaks, it can block the flow of air through the core and kill heat
and will also have an impact on AC. If the system seems to work
intermittently, it's a good indication that the door is broken and
rattling around randomly blocking or opening the passage to the core.
For diagnostic information on how to check the operation of the blend
door and a cheap easy fix, check the heatertreater listing on Ebay or
the web site at heatertreater.net. The dealer fix for the blend door is
basically the same procedure for replacing the heater core, so it will
be expensive. The HeaterTreater alternative will solve the problem at a
fraction of the cost and work and is well within the capability of the
average shade tree mechanic.
You can try to fix it yourself if you check THIS VIDEO
: Ford Expedition Lincoln Navigator