Heater Core Case: Service and Repair
Heater Core
Special tools, testers and auxiliary items required
• Hose Clamps, Up to 40 mm (3094) and
• Hose Clamps Up to 25 mm Diameter (3093)
• Compressed air gun, commercially available
• Cooling System Tester (V.A.G 1274) (and corresponding adapter)
- Switch off ignition.
- Dissipate pressure in coolant circuit by opening cap at coolant expansion tank.
• Depending on the engine and type of vehicle, it may be necessary to loosen or remove various engine components in order to be able to remove the coolant hoses.
Components, that must be removed on 4 cylinder engines
• The following describes removal and installation on a 2.0L TFSI vehicle. The procedure may be different on 4 cylinder vehicles.
- Disconnect electrical connector - 3 - on Mass Air Flow (MAF) Sensor (G70).
- Open spring clips - 1 - and - 2 - and remove air guide hose from mass airflow sensor.
- Remove the air intake from lock carrier - 4 -.
- Remove engine cover.
Components, that must be removed on 5 cylinder engines
- Remove the air guide pipe (from the air filter to the turbocharger).
Components, that must be removed on 6 cylinder vehicles
• The following describes removal and installation on a 3.2L MPI vehicle. The procedure may be different on other 6 cylinder vehicles.
- Remove vacuum hose to brake booster - arrow -.
Procedure continued for all vehicles
- Remove components that block access to the coolant hoses - A - and - B - in engine compartment.
• Depending on the engine and version of the vehicle, it may be necessary to loosen or remove the following components: upper engine cover, pressurized air pipe to throttle valve part, for coolant hose and expansion valve connection area heat shield, etc.).
- Mark the arrangement of coolant hoses - A - (supply to cylinder head) and - B - (return to coolant pump).
• The heater core is designed for a specific coolant flow direction. Therefore, coolant hoses must be connected on the correct sides.
• Bleed the coolant circuit.
- Slide back thermal protective covers - D - and - E - far enough that (VAS 3093) - F - can be installed on the coolant hoses - A - and - B -.
- Clamp off coolant hoses - A - and - B -.
- Clamp off the ventilation hose - C - (to coolant expansion tank), with a (3094) - G -.
- Cover the area beneath connections for coolant hoses - A - and - B -, for example, with a paper towel.
- Remove coolant hoses - A - and - B - from connections to A/C unit heater core.
- Connect a section of hose - A - onto upper connection.
- Hold a container - B - under the lower connection - C -.
- Using a compressed air gun, carefully blow coolant out of heater core (into container - B -).
- Remove bolt - A - from connector flange - B - (so that coolant pipes can be moved to remove heater core).
- Remove storage compartment on driver side.
- Remove front part of center console.
- Remove left footwell vent - A - (driver side).
- Remove the bracket - B -.
If it is necessary, bend lower part of instrument panel - A - to the side to remove the bracket - B -, cover - C - and heater core. Carefully bend it only as far as necessary for removal so that the instrument panel is not damaged.
Removing
- Remove 4 bolts - A - and remove cover - B -.
• This illustration shows an A/C unit with an auxiliary air heater heating element (Z35).
• There are different versions of the cover - B - (for vehicles without or with auxiliary air heater heating element (Z35) ). Refer to Electronic Parts Catalog (ETKA).
• If the lever - C - to the left temperature door is located unfavorably so that the upper bolt - A - is not accessible, switch ignition on and set another temperature setting on the Climatronic control module (J255) (for example, turn temperature adjuster to "Warm" end position).
- Cover carpet in area under heat exchanger with waterproof foil and absorbent paper towel.
- Remove bolts - A - and remove clamps - B - from connections of coolant pipes - C - and - D - at heater core - E -.
- Disconnect coolant pipes - C - and - D - from heater core - E - (slide coolant pipes toward the bulkhead).
- Pull heater core - E - out of heating and A/C unit.
If it is necessary, bent lower part of instrument panel - A - to side to remove heater core - E -. Carefully bend it only as far as necessary for removal so that the instrument panel is not damaged.
Installing
Installation is carried out in the reverse order while noting the following:
- Check the heater core seals - A - and - B -.
• Seal may curl up on insertion if not correctly bonded on.
• Cold air may flow past heater core if seal is damaged or not properly fitted.
• Additional foam strips - A - are attached to the corners of the heater core - B -. The foam strips - A - are supposed to stop any rattling noises, which are common on diesel vehicles. Install the strips on all heat exchangers (use self-adhesive foam strips, part number 191 819 069, refer to the Electronic Parts Catalog).
- With the heater core removed, check heating and A/C unit for soiling (via heater core opening - A -).
- Remove any dirt or coolant still inside the A/C unit (heater) after the heat exchanger is removed.
- Slide heater core into A/C (heating) unit.
- Remove old clamps - B - from both coolant pipes - C -.
- Install new clamps - B - (delivered with heater core) on both coolant pipes for heater core according to illustration.
- Moisten new seals - A - (included in heater core delivery casing) lightly with coolant.
- Insert new seals - A - into connections of heater core - D -.
- Push both coolant pipes - C - into heater core connections - D -.
- Check seating of seals - A - again between coolant pipes - C - and connections of heater core - D -.
- Secure both coolant pipes - C - and - D - with clamps - B - on heater core.
- Tighten bolts on clamps - A - to 2.5 Nm.
- Check seating of both clamps - B - after tightening bolts - A -, clamps must enclose the flange on heater core and coolant pipe completely and must not touch other components.
- Thread bolt - A - into connector flange - B - (while doing this make sure bolt is actually threaded into the mounting point intended for it).
- Make sure the grommet - C - fits correctly inside the bulkhead.
- Seal flange for coolant pipes to heater core - A - and for expansion valve (to evaporator) - B - at pass-through of grommet - C - with silicon adhesive sealant if necessary (to prevent water from penetrating).
- Connect coolant hoses properly to heater core. Observe markings:
A Supply hose from cylinder head
B Return to the coolant pump
- Reinstall all components removed in reverse order, with the exception of cover for connections on heater core and driver's side storage compartment.
- Check installation position of coolant hoses to heater cores (they must not contact components which grow hot) and position and state of heat protection insulation applied to coolant hoses if necessary (not installed on all engine types).
- Bleed cooling circuit.
• When bleeding coolant circuit, take special care to ensure complete bleeding of heater cores. If there are still air bubbles in the heater core, it may cause the customer to complain of insufficient heating performance in winter or different air temperature from vents at same setting in regulated mode. Refer to=> [ Heating Performance Of A/C System, Checking ] Heating Performance Of A/C System, Checking
• Depending on vehicle equipment and on engine, heat insulation has been applied to coolant hoses, these must not be damaged and must be re-applied after installing.
Check the cooling system for leaks
- Bleed coolant circuit.
- Carefully open coolant reservoir cap (observe safety cautions when opening the cap).
- Increase pressure in coolant circuit, for example, using a hand pump (V.A.G 1274/).
- Check the cooling system for leaks. Pay close attention to the connections between the coolant pipes and the heater core.
- Reinstall cover for connections on heater core, driver's side storage compartment and the remaining components that were removed.