What is the easiest way to change a heater core in a 1999 300m

go to the parts store and get a service manual for this truck as there is a specific procedure to bleed the air out of the heater core or it wont work... also this isn't the easiest thing to do, especially if it has the rear air option as well

Heater core replacement is delicate and it is very easy to damage hard to get parts, including the core itself. This job may be best for a shop to handle. The heater core is located in the heater box, follow the heater hoses from the engine to the passenger side firewall area...

No you do not have to drop the steering column to change the heater core. It should be located under the passenger side of the dashboard. The easiest way to find where it is located would be to look under the hood for two hoses that go from the front of the engine through the firewall and that will tell you exactly where it is located. To replace the heater core you will have to disconnect the two hoses under the hood from the heater core then remove the heater box from underneath the dashboard.

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.

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.

The EASY way, thought not necessarily pretty, but it works... get a rotary cutting tool (ie Dremel) and cut the rectangular cover for the heater core under the dash... one the two heater lines are disconnected, the core should slide right out.... put the new core in, then glue the cut away plastic with RTV silicone seal, re-attach the two hoses, and you're good to go.... otherwise, its a nightmare of pulling out nearly the entire dash, disconnecting the A/C lines, etc. not something I'd want to undertake... so this EASY solution will get the job done, without costing you an arm and a leg at the mechanic.

unfortunately the fastest easiest way is usualy to remove the entire dash and its about a 2 day job

there is no easy way to change out a heater core...you have to take the bottom part of the dash loose and that takes some doing. once you get the bottom of the dash apart you will see the heater core.then you have to go under the hood and unhook both water lines that run to it, you should then be able to pull the heater core out and install the new one

take it to someone that works on cars you wont like the task

I believe this is the easiest heater core ever invented. If it is like the 1986 model. I believe it is. You take out the glove box door. The heater core is right there under a cover in the duct work.