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.
You 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.
If it 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.
It will run fine on 87 Regular. My 2000 Eddie Bauer runs on 87 unleaded regular.
Bolted to the bottom of the engine
P255/70/16
I believe it is 21 U.S. gallons ( 79.5 liters )
On a 2000 Ford Explorer : The ELECTRIC fuel pump is INSIDE the fuel tank ( it is installed through an access hole in the top of the tank )
www . motorcraft service . com ( no spaces ) click on owner guides
Ford Explorer headliner replacement instructions check related link below.
The 2000 Ford Explorer owners manual shows : for the 4.0 L - SOHC - V6 engine ( Motorcraft FL - 1A oil filter )
locks out rear door window switches
www . motorcraft service . com ( no spaces ) Click on Owner Guides
It should be in the compartment that holds your jack, bold numbers stamped on a metal plate.
According to the Owner Guide that is the button for the ( reverse sensing system )