Changing out the heater core (matrix): What do I need to consider?

[Roger Dunning]

My heater core went pop and has me off the road. I am getting orders in for the parts I need and wondered if people have insight into what I should be replacing as well as the heater core, and what parts I am going to need to buy. Alaso any other jobs I should be doing at the same time?

I'm in the UK but typically order from RockAuto.com

Any advice appreciated.

 

[KennethS]

You can bypass the core in order to keep driving while waiting for parts to arrive. Disconnect the two heater hoses from the firewall and connect them to each other.

 

[Rancho LJ]

I'm doing this job om my 05 in fall. Core is currently bypassed as @KennethS suggested.

The evaporator core is inside the HVAC case. I'm changing mine out while I'm inside. I'm also replacing the AC accumulator/drier. Here's the parts list from Rock Auto.

FOUR SEASONS
54837
A/C Evaporator Core

FOUR SEASONS
98028
Heater Core

FOUR SEASONS
83106
A/C Receiver Drier / Accumulator

When I get inside, I'll check the condition of the mode/blend doors.

Also consider a seal kit. When I did my 03 Ram, all the foam seals were destroyed. This seal kit from E/Bay is sold by a forum member. See this thread:

Thread 'HVAC box replacement foam'

Mar 29, 2025

I’m changing the heater core and evaporator on my tj and the foam pieces that seal it at the firewall are hard to make for yourself until I came across an exact copy. This guy said he found an old kit and had an exact copy made so I wanted to share it with other who could benefit from it. https://www.ebay.com/itm/3565193545...pid=5337789113&customid=&toolid=10001&mkevt=1

• ChrisTJ98
• Replies: 64
• Forum: TJ General Discussion

• 
• 

 

[DirtDawg]

My 2005 TJ has the heater hoses bypassed, with prior core leakage likely the reason. Watching replacement vids discouraged DIY, noting my this TJ is a dedicated trail rig. With that, figured I'd just dress warmly when used off-pavement during winter months at 7k+ elev. Nonetheless, I'd much rather have the entire HVAC system functioning normally, plus the fresh and cooled air volume felt at vent registers is less than normal (having owned a 2000 TJ from new for 20 yrs). I did replace the control panel with an aftermarket SMP HS-373, which required rerouting the vacuum line bundle to HVAC connector, however net result wasn't much (if any) different. I also have a Dorman 973-025 resistor ready to install, however doing that same time as a new blower motor seems prudent, along with the task I've avoided being R&R of the entire HVAC box along with its internal core. So then, I'll be monitoring this topic for subsequent replies...

 

[oldjeepman]

Also possible blower motor..

 

[Roger Dunning]

I'm doing this job om my 05 in fall. Core is currently bypassed as @KennethS suggested.

The evaporator core is inside the HVAC case. I'm changing mine out while I'm inside. I'm also replacing the AC accumulator/drier. Here's the parts list from Rock Auto.

FOUR SEASONS
54837
A/C Evaporator Core

FOUR SEASONS
98028
Heater Core

FOUR SEASONS
83106
A/C Receiver Drier / Accumulator

When I get inside, I'll check the condition of the mode/blend doors.

Also consider a seal kit. When I did my 03 Ram, all the foam seals were destroyed. This seal kit from E/Bay is sold by a forum member. See this thread:

Thread 'HVAC box replacement foam'

Mar 29, 2025

I’m changing the heater core and evaporator on my tj and the foam pieces that seal it at the firewall are hard to make for yourself until I came across an exact copy. This guy said he found an old kit and had an exact copy made so I wanted to share it with other who could benefit from it. https://www.ebay.com/itm/3565193545...pid=5337789113&customid=&toolid=10001&mkevt=1

• ChrisTJ98
• Replies: 64
• Forum: TJ General Discussion

• 
• 

This is awesome. I really appreciate it.

 

[Roger Dunning]

I'm doing this job om my 05 in fall. Core is currently bypassed as @KennethS suggested.

The evaporator core is inside the HVAC case. I'm changing mine out while I'm inside. I'm also replacing the AC accumulator/drier. Here's the parts list from Rock Auto.

FOUR SEASONS
54837
A/C Evaporator Core

FOUR SEASONS
98028
Heater Core

FOUR SEASONS
83106
A/C Receiver Drier / Accumulator

When I get inside, I'll check the condition of the mode/blend doors.

Also consider a seal kit. When I did my 03 Ram, all the foam seals were destroyed. This seal kit from E/Bay is sold by a forum member. See this thread:

Thread 'HVAC box replacement foam'

Mar 29, 2025

I’m changing the heater core and evaporator on my tj and the foam pieces that seal it at the firewall are hard to make for yourself until I came across an exact copy. This guy said he found an old kit and had an exact copy made so I wanted to share it with other who could benefit from it. https://www.ebay.com/itm/3565193545...pid=5337789113&customid=&toolid=10001&mkevt=1

• ChrisTJ98
• Replies: 64
• Forum: TJ General Discussion

• 
• 

I'm a right hand drive as in UK so I switched up the heater core. I think I will double check with them to ensure it is all good.

 

[Rancho LJ]

Yes, please confirm all part numbers in case I got something wrong. Good luck!

 

[Roger Dunning]

My 2005 TJ has the heater hoses bypassed, with prior core leakage likely the reason. Watching replacement vids discouraged DIY, noting my this TJ is a dedicated trail rig. With that, figured I'd just dress warmly when used off-pavement during winter months at 7k+ elev. Nonetheless, I'd much rather have the entire HVAC system functioning normally, plus the fresh and cooled air volume felt at vent registers is less than normal (having owned a 2000 TJ from new for 20 yrs). I did replace the control panel with an aftermarket SMP HS-373, which required rerouting the vacuum line bundle to HVAC connector, however net result wasn't much (if any) different. I also have a Dorman 973-025 resistor ready to install, however doing that same time as a new blower motor seems prudent, along with the task I've avoided being R&R of the entire HVAC box along with its internal core. So then, I'll be monitoring this topic for subsequent replies...

I had a really interesting conversation with the chap who originally created the Rubicon! He's a brit and someone introduced me. When I said that I had a heater core gone he was surprised. He asked me if the radiator was ok, and I explained that it had just been replaced. He then said that the rad is the least path of resistance for a system that is over pressured, with the heater core (matriX) following after. Since both had gone he suggested that it could possibly be a head gasket that was the actual root cause. Hew was quick to say that it may not be but it was the first place he would check.
Super interesting guy and my god he knew his stuff.

I've managed to get a heater core and I'm having that replaced next week. I will also be getting them to test for the head gasket.

 

[ColoJeep]

I had a really interesting conversation with the chap who originally created the Rubicon! He's a brit and someone introduced me. When I said that I had a heater core gone he was surprised. He asked me if the radiator was ok, and I explained that it had just been replaced. He then said that the rad is the least path of resistance for a system that is over pressured, with the heater core (matriX) following after. Since both had gone he suggested that it could possibly be a head gasket that was the actual root cause. Hew was quick to say that it may not be but it was the first place he would check.
Super interesting guy and my god he knew his stuff.

I've managed to get a heater core and I'm having that replaced next week. I will also be getting them to test for the head gasket.

You could test / replace your radiator cap . that is the " pressure regulator " for the whole system .