There will be two ports with caps on the lines running from the a/c cmpressor. The smaller one is the low side.
On a 2004 Mercury Mountaineer : The ELECTRIC fuel pump is INSIDE the gas tank
In the right front passenger footwell , by the kick panel
The electric fuel pump is inside the fuel tank
According to the 2004 Mercury Mountaineer Owner Guide : ( 22.5 U.S. gallons )
The 2004 Mercury Mountaineer does not have an automatic transmission fluid dipstick . I know that the 2002 and newer Ford Explorer four door versions do not have a dipstick for the automatic transmission fluid level .
fuel gauge not working and power windows and radio.2004 mercury mountaineer.
wheel bearings mountaineer 2004
# 24 is a 15 amp fuse for the cigarette lighter , OBD II , in the passenger compartment fuse panel of a 2004 Mercury Mountaineer
A door panel on a 2004 Mercury Mountaineer is held on by several screws. Once all the screws are removed the panel can easily come off.
Starting with the 2002 model , there is no automatic transmission fluid dipstick on the Mercury Mountaineer ( and the Ford Explorer , 4 door )
Max capacity is 22.5 gallons.
Disconnect the negative side of the battery