Heater Core, Removing And Installing: Installing

WARNING: This page is about a different car, the 2023 Audi S3, 2023 Audi RS 3, 2023 Audi A3 Quattro, and 2023 Audi A3. However, it is still accessible from the selected car via links, so may be relevant.

Install in the reverse order of removal while noting the following:

Replace the seals. Refer to the Parts Information for the correct version.

-- With the heater core removed, check the heater shaft for debris.

-- If necessary, remove any dirt or coolant residue.

-- Vehicles with a TDI engine: check the heating element shaft for debris when the auxiliary heater heating element is removed and clean if necessary.

-- If equipped, check the foam seals -2- attached to the heater core -1- for damage and replace if necessary.

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The foam seals -2- depending on the version and the production time is not always present.
If not bonded correctly, the foam seal may curl up during insertion.
Cold air may flow past the heater core if the foam seal is damaged or not properly installed.

-- Check the heater core connection -3- and the connection -2- for the coolant pipes for damage or debris.

Fig 1: Heater Core Connections, Coolant Pipe And O-Ring Seal

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-- Clean and smooth the sealing surface for the O-ring.

-- Coat the new O-ring -4- with coolant and place on the coolant pipe -1-.

-- Carefully slide the heater core all the way into the heater and A/C unit until stop.

When inserting the heater core, make sure that the connections and the coolant pipes are not damaged.

-- Slide the coolant pipes into the heater core until stop.

CAUTION:

There is a risk of heater core malfunctions due to faulty seals and leaks.

- Never pinch the seals.

- Never tilt the coolant pipes.

- Slide the coolant pipes on all the way.

-- If a new cover cannot be attached to the heater core, cuts must be made on the rubber support -arrows- as shown.

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-- Position a new securing clip -5- or screw-type clamp -2- on the coolant pipe/heater core connection.

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-- Tighten the bolt -3-. Refer to OVERVIEW - HEATER AND A/C UNIT .

-- Check the clamp and screw-type clamp for proper seating on the heater core and the coolant pipe connections. They must not be touching the air distribution housing or any other components.

-- Fill the coolant. Refer to COOLANT, DRAINING AND FILLING .

-- Check the DTC memory and erase any displayed entries using the Vehicle Diagnostic Tester in the "Guided Fault Finding" function.

-- Check the heating and A/C system function.