Heater Core: Service and Repair
Heat Exchanger
Special tools, testers and auxiliary items required
• Drip tray (V.A.G 1306)
• Hose clamps up to dia. 40 mm (VAS 3093)
• Compressed air gun, commercially available
Removing
- Place Drip tray (V.A.G 1306) under the engine.
CAUTION!
Contact with hot engine coolant can cause severe scalding.
Coolant temperature can be above 100 °C with a warm engine. The cooling system is under pressure.
If necessary, reduce pressure and temperature before repairs.
- Clamp off coolant hoses - 1 - using hose clamps up to dia. 40 mm (VAS 3093) and disconnect coolant hoses to heater core.
- Connect a section of hose - A - onto upper connection of heater core.
- Hold a container - B - under the lower connection - C -.
- Using a compressed air gun, carefully blow coolant out of heater core into container - B -.
Depending on the engine, additional parts may need to be removed such as the charge air pipe.
- Slightly loosen (do not remove) screw (6 mm hex socket head) - 1 - on connecting flange between heater core connections.
• By loosening the screw - 1 -, the coolant pipes are loosened and it is easier to remove the heater core.
- Remove driver side footwell trim
- Remove left footwell vent => [ Left Footwell Vent ] Vents.
- Remove screws - A - and remove trim - B -.
• There are different versions of cover - B -.
• The illustration shows the version with Auxiliary Air Heater Heating Element (Z35).
• If the temperature door lever - C - is a position that hinders access to the upper screw - A -. Change the position of the temperature door using the controls for hot air and fresh on, on vehicles with Climatronic with operating and display unit (e.g. "Hi" setting).
- Cover carpet in area under heat exchanger with waterproof foil and water absorbing paper.
- Open pipe clamps - A - and disconnect coolant pipes from heater core.
- Remove heater core from heating unit.
Installing
Installation is carried out in the reverse order, when doing this note the following:
- Check seals - A - and - B - installed on heater core, only install a heater core with undamaged seals.
• An incorrectly glued seal can roll up into heating unit when sliding in the heater core.
• Cold air may flow past heat exchanger if seal is damaged or not properly fitted.
- With the heater core removed, check heating unit for soiling (via heater core opening - A -).
- If necessary, remove dirt or coolant from heating unit, for example after removing leaky heater core.
- Push heater core into heating unit.
- Coat sealing rings - 1 - with coolant before installing.
- Insert sealing rings - 1 - into connection on heater core.
• Ensure sealing rings are installed on the proper side, as shown in the illustration.
• If pipe clamps are deformed, replace them.
- Connect coolant pipes to heater core.
- Pipe clamps - A - must be able to be twisted slightly when installing onto the coolant pipes.
- Pipe clamps - A - must be installed as shown in the illustration.
- Tighten the pipe clamps - A - to 2 Nm.
- Check seating of both clamps - A - after tightening screws. They must completely enclose the flange on the heat exchanger and coolant pipe and must not come in contact with other components.
- Tighten the screw - 1 - from the connecting flange between heater core connections to 2 Nm.
- Check position of grommet - C - in bulkhead for proper seating.
- Seal the flanges on the coolant pipes leading to the heater core - A - and for the expansion valve to the evaporator (only on vehicles with air conditioning) - B - at the pass-through of grommet - C -with silicon adhesive sealant if necessary, to prevent water from penetrating.
• Sealing rings must always be replaced.
• After replacing heater core, coolant must be replaced completely19 General Information.
• Check coolant circuit for leaks, pay particular attention between coolant hoses and heater core.