Replace heater core in 1994 mearcury villager

Hi Shawn,your thermostat may be stuck open,not letting your coolant heat up.check this first.here's a link on how to replace, GET 25 GIFT CARD FOR EVERY 100 SPENT ON ONLINE SHIP TO HOME ORDERS After removing,look at it,it should be closed,to see if it is working,boil water to 180 degrees with thermostat in pot,it should open at 180,remove from water and it should close,if it's doing this,then it's good,is your water pump working properly,no leaks.Here's another link to your heater core, GET 25 GIFT CARD FOR EVERY 100 SPENT ON ONLINE SHIP TO HOME ORDERS I am fixing to replace my heater core in my 85 Nissan 720 truck,did it 10 years ago,my heat still works,but my windows fog up super fast,which means it's leaking,can put my hand on the carpet by the heater core and feel coolant,it's a job.

Answer for a 1995 F250:

Remove the glove-box door. Behind that is the heater core cover on the interior, passenger side of the firewall. Remove that cover and there is the heater core. Open the hood and look where the heater hoses enter the front right passenger area of the exterior side of the firewall. Disconnect the two heater hose clamps and you can then remove the heater core.

Considering that your vehicle and the Nissan Quest are covered by the same service manual from Haynes, they might well have the heater core in common too:
Villager/Quest manual

If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

The heater housing is disassembled to get to the heater core. Heater Core

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.

When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.

If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

The heater housing is disassembled to get to the heater core. Heater Core

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.

When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.

Off the heater hoses that connect to the heater core on back of motor by firewall.

behind glove box!
Inspect/Replace If it is necessary to remove the heater assembly, the cooling system must be drained before removing the heater core.
When a heater core leaks, a new heater core is installed or the old one repaired.
Heater Housing

• The heater housing is usually under the dash and must be removed to gain access to the heater core.
• Procedures for replacing the heater core vary with the year, make, and model of car. It threfore necessary to consult the manufacturer's repair manuals for the proper procedure for replacement.

The heater housing is disassembled to get to the heater core.
Heater Core

• Remove the access panels(s) or the split heater/air conditioning case to gain acess to the heater core.
• Remove the heater coolant hoses.
• Remove the cable and/or vacuum control lines (if equipped).
• Remove the heater core securing brackets and/or clamps.
• Lift the core from the case. Do not use force. Take care not to damage the fins of the heater core when removing.
• To reinstall the heater core, reverse the removal steps.

When the heater core leaks and must be repaired or replaced, it is a very difficult and time-consuming job primarily because of the core's location deep within the firewall of the car. For this reason always leak test a replacement heater core before installation.

As with all vehicles it seems the first part that they build around is the heater core. It is under the dash above the floor housed in a black plastic sealed box. Sealed with goop. Locate that box and start removing everything around it that is peventing taking the cover off. Of course disconnect the heater hoses under the hood a thefirewall.

Warning it is never as easy as it sounds.

You will need to pull the dash assembly away from the firewall slightly and remove duct work from heater case on right (passenger)side then the heater core cover,the 2 bands that secure heater core,drain cooling system,remove the 2hoses,and swop out old heater core.

your heater core may be getting blocked up, or the thermostat may be stuck open at times. you have a few options here, option 1 and 2 cost about the same, option 1: have the thermostat replaced just so you know its working properly, a 97 will most likely not have a telltale way of knowing if the thermostat is bad or going bad. option 2. have the cooling system flushed at a shop. this will try to clear out and debris in the cooling system that may be blocking passages or the heater core. option 3 is the most expensive. have the heater core replaced, the heater core is what provides heat to the hvac system in the dash. a few other things to check would be vacuum lines/actuator/temperature door on your hvac system.