Replacing the heat exchanger for heating system (heating and air-conditioning unit removed)

WARNING: This page is about a different car, the 2025 BMW M4, 2024 BMW M4, 2023 BMW M4, 2022 BMW M4, and 2021 BMW M4. However, it is still accessible from the selected car via links, so may be relevant.

Removing the left air distribution flap motor (M21b)

NOTE: For a better overview the removed condition is shown here.

Disconnect plug connection (1).
Loosen screws (2).
Remove left air distribution flap motor (3).

Courtesy of BMW OF NORTH AMERICA, INC.

Remove rear blender flap motor (M23b)
Disconnect plug connection (1).
Loosen screws (2).
Remove the rear mixed air flap motor (3).

G15340928

Courtesy of BMW OF NORTH AMERICA, INC.

Remove the coolant pipe below

Disassemble the retaining clip (1) as described in the next step.

Courtesy of BMW OF NORTH AMERICA, INC.
Unlock the retaining clip (1) upwards using a suitable screwdriver.
Move the retaining clip to the side (2) with a suitable screwdriver.
Set the coolant pipe aside.

G15340930

Courtesy of BMW OF NORTH AMERICA, INC.

Removing the kinematics at the bottom left

Detach the cable from the cable guide (1).
Push the coolant tube (3) downwards.
Unlatch the deflection lever (4).

Loosen screws (2).
Remove the kinematics.

G15340931

Courtesy of BMW OF NORTH AMERICA, INC.

Remove top coolant pipe

Disassemble the retaining clip (1) as described in the next step.

Courtesy of BMW OF NORTH AMERICA, INC.
Unlock the retaining clip upwards (1) using a suitable screwdriver.
Move the retaining clip to the side (2) with a suitable screwdriver.
Set the coolant pipe aside.

G15340933

Courtesy of BMW OF NORTH AMERICA, INC.

Remove heat exchanger

Loosen screws (1).
Remove heat exchanger (2).

G15340934

Courtesy of BMW OF NORTH AMERICA, INC.

Replace the heat exchanger for interior heating.
Parts: Heat exchanger

Installing the heat exchanger
Position the heat exchanger (2).
Tighten down screws (1).

TIGHTENING TORQUES SPECIFICATION

Heater/air conditioner
Screw	Tightening torque	1.2 Nm

G15340935

Courtesy of BMW OF NORTH AMERICA, INC.

Installing the coolant tube at the top

Replace the sealing ring.
Parts: Sealing ring
Position the coolant pipe.
Secure the coolant pipe with the retaining clip (1).
Ensure that the coolant pipe is correctly fitted on the heat exchanger.

G15340936

Courtesy of BMW OF NORTH AMERICA, INC.

Install the kinematics at the bottom left

Insert and position the kinematics (2).
Ensure that the guide pin (1) is correctly positioned in the guide of the link disk (2).

Courtesy of BMW OF NORTH AMERICA, INC.
Position the kinematics.
Tighten down screws (2).

TIGHTENING TORQUES SPECIFICATION

Heater/air conditioner
Screw	Tightening torque	1.2 Nm

G15340938

Courtesy of BMW OF NORTH AMERICA, INC.

Engage the deflection lever (4).
Ensure that the deflection levers (4) audibly engage.
Position the coolant pipe (3).
Attach the cable in the wire guide (1).

Installing the lower coolant tube

Replace the sealing ring.
Parts: Sealing ring
Position the coolant pipe.
Secure the coolant pipe with the retaining clip (1).
Ensure that the coolant pipe is correctly fitted on the heat exchanger.

G15340939

Courtesy of BMW OF NORTH AMERICA, INC.

Installing the left air distribution flap motor (M21b)

Position the left air distribution flap motor (3).
Tighten screws (2).

TIGHTENING TORQUES SPECIFICATION

Heater/air conditioner
Screw	tightening torque	1.2 Nm

G15340940

Courtesy of BMW OF NORTH AMERICA, INC.

Connect connectors (1) and lock.

Install the rear passenger compartment blending flap motor (M23b)

Position the rear mixed air flap motor (3).
Tighten down screws (2).

TIGHTENING TORQUES SPECIFICATION

Heater/air conditioner
Screw	tightening torque	1.2 Nm

G15340941

Courtesy of BMW OF NORTH AMERICA, INC.

Connect connectors (1) and lock.