To replace 98 dodge avenger heater core, does the entire dash have to be removed?

Tyrone, Check the attached links,instruction and guides, the last link has some very good info. and pics. on S10 heater core replacement. Good luck.
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Heater core replacement 2000 S10 4 3L slideshow picture
How to Change Heater Core on 1994 Chevy 10 Blazer GMC Jimmy Oldsmobile...
98 GMC Jimmy Heater Core Replacement Video Diary
Heater core replacement procedure 99 S10

Lotta work - need to remove dashboard to get to heater core - and before disconnecting heater core hoses you have to remove all coolant from car by draining radiator and opening heater valve to full heat. Remove core, replace with new one and reverse other operations. Make sure to properly refill radiator so there are no air pockets that will restrict coolant flow.

Check out You tube !

Most cars now require removal of the whole dash. Buy a shop manual to guide you step by step.

Ohmigosh ! If it is coolant, feels slippery and smells like it? it is probably the heater core inside the heater case. It can't be fixed, but has to be replaced.
Look under the hood on the firewall where the two heater hoses go in-any sign there of a hose leaking? The hoses go right into tubes or pipes that are soldered to the heater core, so the hoses show you exactly where the heater core is located under the dash.
If you want to attempt changing the heater core, first buy a repair manual for the Frontier. The chapter on heating and cooling will have the heater core removal and replacement procedure, step by step. Read it and see if you want to do it-on some cars or models, it is easy, there is a cover plate to remove and then slide the core out...BUT on a lot of vehicles, the entire instrument panel has to be removed from the car to get to the heater core, a pretty big job. I have taken apart quite a few dashes and instrument panels ( and even put a couple back together), believe me, it is not for the faint hearted. So many screws to keep track of, so many electrical connections to be pulled apart, so much plastic to break. Not trying to dissuade you, just letting you know it can be a bear ! Your local library might have some repair manuals where you could find the procedure for your Frontier. Or stop in at the Nissan dealer and talk to a mechanic or parts person-they might be able to tell you if you have to remove the dash to get to the heater core.

Try to determine if it is coolant. Has enough leaked out yet that your coolant level in the radiator is low?

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

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.

For heater core replacing procedure. I suggest you to go through this related help links.Its all complete step by step procedure: ----How to replace heater core for All car models?

Click the link below: ---

http://technoanswers.blogspot.com/2011/11/how-to-replace-heater-core-for-all-car.html

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How to Flush Heater Core?

http://schematicsdiagram.blogspot.com/2011/12/how-to-flush-heater-core.html

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How to Remove Heater Core ?

http://howtobyme.blogspot.com/2011/12/how-to-remove-heater-core-on-2008-honda.html
Heater Core Replacement?

http://howtobyme.blogspot.com/2011/12/honda-heater-core-replacement.html

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To replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on.html------

How to replace heater core?http://technoanswers.blogspot.in/2012/02/how-to-replace-heater-core-on_10.html
----------This will help.Thanks.

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.

this repair is very extensive if you have limited ability then do not attempt,,,,,, the steering column has to be dropped. entire dash removed, ac freon recovered coolant drained below core then the heater box assembly has to be removed as a whole then disassemble heater box to replace the core then reverse procedure.