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Heater Core Replacement
 
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Pelican Technical Article:

Heater Core Replacement

Nick Czerula

Time:

4 hours4 hrs

Tab:

$150

Talent:

*****

Tools:

T27 Torx driver, flathead & Phillips head screwdriver, trim panel tool, diagonal cutters

Applicable Models:

BMW Z3 (1996-02)

Parts Required:

Heater core, heater core O-rings and coupler clips, engine coolant

Hot Tip:

Drain cooling system before beginning

Performance Gain:

Remedy a coolant leak

Complementary Modification:

Flush cooling system

BMW Z3 models are equipped with a climate control system or HVAC (called IHKA by BMW) that automatically controls cabin temperature once a temperature is set on the HVAC control head in the center dashboard. IHKA controls air-conditioning, heating, internal blower motor operation and numerous air outlets. The electronic IHKA control module governs the operations of the following components:

  • Heater valve in engine compartment - controls the flow of hot coolant to the heater core inside the IHKA housing (heater box) underneath the center dashboard.
  • AC compressor in the engine compartment - driven by engine accessory belt.
  • Blower motor underneath the dashboard behind the glove compartment - motor speed modulated using the blower final stage.
  • Air outlets - electric stepper motors attached to vent flaps control the flow of fresh or recirculated cold and warm air to windshield, face-level vents and foot wells.
  • Engine cooling fan - IHKA microprocessor and engine control module (ECM) determine operation and speed of cooling fan.

The heater core is a small radiator located in the heater box. Hot coolant flows through the heater core. Air from the blower motor is passed over the heater core and enters the passenger cabin, heating the interior. The heater core can develop leaks. A sign that you have a heater core leak is a film on the inside of your windshield or a coolant leak on the interior vehicle floor. Should you have a leak, you'll probably also smell the coolant in your cockpit. To check for a coolant leak, first check your coolant level. If low, pressure-test the cooling system. Check for coolant exiting the heater box drain, located under the vehicle near the transmission tunnel. Or check for coolant leaking onto the passenger floor. The center console has to be removed to replace the heater core, but the heater box can stay in place. Be sure to purchase O-rings and heater core plastic coupler clips when replacing your heater core.

Do not remove the radiator or expansion tank cap or work on any other part of the cooling system while the engine is hot. Coolant or hot steam may escape and will scald you. To do any work on the cooling system, wait until the engine has cooled off.

To avoid marring the paint and trim, work with a plastic prying tool or wrap a screwdriver tip with masking tape before prying out body or interior items.

Keep in mind that when your car was serviced before, parts may have been replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have, so be prepared with different size sockets and wrenches. 

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Do not work on your vehicle if you feel the task is beyond your ability. 

Vehicle models change and evolve, as they grow older, so the vehicle shown in our illustrations may vary slightly from yours. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

Working at the driver side knee bolster, remove the plastic trim caps (yellow arrow) from the screws.
Figure 1

Working at the driver side knee bolster, remove the plastic trim caps (yellow arrow) from the screws. Use a small flathead screwdriver and lever the caps off. Then remove three Phillips head screws (green arrows).

Next remove the remaining Phillips head screws (green arrows) from the knee bolster trim panel.
Figure 2

Next remove the remaining Phillips head screws (green arrows) from the knee bolster trim panel. Remove the plastic caps as you did previously if they are present. I find these caps missing quite often. There should also be Phillips head screws (yellow arrow) that run along the bottom edge of the knee bolster trim panel, remove these as well.

Pull knee bolster (green arrow) down and away from dashboard and remove.
Figure 3

Pull knee bolster (green arrow) down and away from dashboard and remove.

Next you will have to remove the knee support.
Figure 4

Next you will have to remove the knee support. Remove all six 10mm bolts (green arrows) from the support. When you get to the final bolt, hold the support in place or it will fall down.

Remove the knee support from the vehicle.
Figure 5

Remove the knee support from the vehicle. Then remove the center console. See our tech article on center console removing.

Working at the left side of the center console in front of the heater core (yellow arrow), remove the two 10mm support bracket fasteners (green arrows).
Figure 6

Working at the left side of the center console in front of the heater core (yellow arrow), remove the two 10mm support bracket fasteners (green arrows). Then remove the support bracket.

Next you have to remove the electrical connector that is mounted near the heater hose connections.
Figure 7

Next you have to remove the electrical connector that is mounted near the heater hose connections. Start by cutting the zip tie strap (green arrow). Then pull the connector down and away from the heater pipes.

With the connector removed, pull the plastic mount off the heater pipes.
Figure 8

With the connector removed, pull the plastic mount off the heater pipes. This is the mount for the electrical connector.

You have two choices when it comes to dealing with the coolant in your engine.
Figure 9

You have two choices when it comes to dealing with the coolant in your engine. You can either drain the cooling system or clamp off the heater hoses. If the coolant in the vehicle is in good condition, I clamp the hoses to avoid the draining process. I use hose clamp pliers shown in this photo. One is currently clamping a heater hose (green arrow) and the other will be used to clamp the remaining heater hose. Keep in mind, if your hoses are in poor shape, this method could damage or shorten the hoses lifespan. So use your best judgment when utilizing the clamping method.

Now it is time to disconnect the heater pipe connections to the heater core.
Figure 10

Now it is time to disconnect the heater pipe connections to the heater core. Start by squeezing the plastic coupler retainers. Then slide the black plastic coupler (green arrows) toward the firewall. The yellow arrow points to one of the two release tabs on the plastic coupler. You will have to press both. The red arrow points to a release tab I cut to make sliding the coupler easier. This method works great. You are going to replace the retainers anyway. Just be careful not to damage the plastic coupler.

Place a drain pan under the heater hoses.
Figure 11

Place a drain pan under the heater hoses. I use an old coolant bottle (green arrow) with the side cut out. This will help catch any dripping coolant.

Next, remove the T20 Torx heater pipe mounting screw (green arrow).
Figure 12

Next, remove the T20 Torx heater pipe mounting screw (green arrow). Note the position of my Torx driver (yellow arrow).

Next, remove the two T20 Torx heater core mounting screws (green arrows).
Figure 13

Next, remove the two T20 Torx heater core mounting screws (green arrows).

Grab the heater core and begin to feed it out of the heater box in the direction of the yellow arrow.
Figure 14

Grab the heater core and begin to feed it out of the heater box in the direction of the yellow arrow. As you remove it, pull the heater core pipes out of the heater hose pipes at the firewall. Once the pipes are detached, remove the heater core from the vehicle (yellow arrow).

With the heater core removed, check the heater hose pipes.
Figure 15

With the heater core removed, check the heater hose pipes. Be sure the plastic bushings are removed (green arrow). There might be one left in each pipe. Pull them out and discard.

Attach new foam seals to the heater core.
Figure 16

Attach new foam seals to the heater core. Start to feed the new heater core into the heater box. Once the heater core pipes are close to the heater hose pipes, install the new O-rings, spacers and bushings onto the heater core pipes. This photo shows the sealing O-rings, spacers and bushings as they come new (insets). Note the O-rings, spacers and bushing orientation (green arrow) on the heater core pipe. I like to coat the O-rings with liquid soap to make installing them easier. Once the O-rings, spacers and bushings are on the heater core pipes, slide the heater core pipes into the heater hose pipes. Be careful not to pinch the O-rings. You will need patience for this portion of the procedure as it can be challenging. Aligning all four O-rings and sliding the pipes in can be tough. Use a dull pick or flathead screwdriver to guide the O-rings into the pipe if needed. Once the pipes are joined, slide the plastic coupler over the retaining clips and listen for an audible click. Be sure these clips engage 100%. When you have these clips fully attached, pressure test the cooling system to be sure it is sealed. Then reassemble the vehicle in reverse of disassembly. Fill and bleed the cooling system and check the heater's functionality.


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Comments and Suggestions:
Ryan Comments: Hi, What is the part number for the new seals/retainers in yellow Figure 16?
November 20, 2016
  Followup from the Pelican Staff: http://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=DWsearch&description=64118398888&I1.x=0&I1.y =0 - Nick at Pelican Parts  
Dave Starr Comments: Do you have the same technical bulletin to replace the heater core for a 2002 BMW 330 Ci Coupe?
November 19, 2015
  Followup from the Pelican Staff:
We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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Page last updated: Sat 12/3/2016 02:38:35 AM