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Autopapyrus · Mercedes-Benz E-Class W211
https://autopapyrus.com/guides/mercedes-benz/e-class/heater-core-replacement/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mercedes-Benz E-Class W211: Heater Core Replacement

Replacing the heater core on the W211 is one of the most labor-intensive jobs on this car, because the heater core sits inside the HVAC housing under the center section of the dashboard. Access requires removing the upper and lower dashboard sections, the center console, the steering column, and the metal cross-car beam. The procedure includes draining the coolant, disconnecting the heater hoses, disassembling the climate control housing, and bleeding the cooling system after installation. It is critical to follow the sequence and avoid damaging the electronics and airbags.

Difficulty: Hard Time: 8-12 hours (for an experienced technician), up to 2-3 days for a beginner Steps: 17 Tools: TORX socket set (T20, T25, T30), socket set and ratchet, hose clamp pliers, flathead and Phillips screwdrivers, coolant drain pan (10 L (10.6 qt)), airbag safety precautions (disconnect the battery negative terminal and wait 15 minutes)

Part

  • 🔩 Heater core A2118300361 or 2118300361 (diesel versions may differ in the auxiliary electric heater, part number A2118300761). Aftermarket alternatives: Nissens, Behr-Hella, NRF. Coolant MB 325.0 (specification MB 325.0): 4-5 L (4.2-5.3 qt) of concentrate plus distilled water, or pre-mixed coolant
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 9 more. See manuals →

Step by step

17 steps
  1. Prepare the vehicle: disconnect the battery negative terminal and wait 15 minutes for the airbag capacitors to discharge. If it is cold outside, bring the car into a warm garage for a few hours so the interior plastic warms up and doesn't crack during disassembly.
  2. Drain the coolant: place a drain pan under the drain plug at the bottom of the engine radiator, remove the plug, and drain about 7-8 L (7.4-8.5 qt) of coolant (the total system capacity is about 9.5 L (10 qt), but not all of it drains out). Open the expansion tank cap to speed up the process.
  3. Remove the lower part of the center console: remove the TORX screws around the perimeter of the lower trim panel under the steering column, and carefully release the clips (if they are brittle, use a plastic trim tool). Remove the steering column trim, disconnecting the connectors for the buttons and switches.
  4. Lower the steering column: remove the steering column mounting bolts (usually 4 bolts, 13 mm socket) and lower the column, without disconnecting it completely (it is enough to free up working space). There is no need to remove the steering wheel unless necessary.
  5. Remove the center console and the upper part of the dashboard: remove all TORX screws securing the center console (including those hidden under covers near the cup holders and armrest). Remove the climate control panel, carefully disconnecting the connectors. Remove the center air vents. Remove the screws securing the upper dashboard section (around the perimeter and under the vents), then carefully pull the panel toward you to release the clips. Disconnect all connectors that interfere with removal.
  6. Remove the metal reinforcement beam: under the instrument panel is a metal cross-car reinforcement beam. Remove all of its mounting bolts to the body (usually 6-8 bolts, 13-15 mm sockets). The beam is heavy, so support it while removing the last bolts. Remove the beam.
  7. Access the climate control housing: the HVAC housing (a large plastic unit in the center under the dash) is now visible. Disconnect the electrical connectors of the blend door actuators (usually 3-5 connectors around the housing). Remove the screws securing the housing to the body (usually 4-6 TORX T25 or T30 screws).
  8. Disconnect the heater hoses: in the engine compartment, locate the two heater hoses (they pass through the firewall on the right side of the OM646 engine). Loosen the clamps with pliers and carefully pull the hoses off the heater core pipes (residual coolant will run out, so place a pan underneath). Plug the hoses with rags or plugs to keep coolant from dripping into the cabin.
  9. Disassemble the climate control housing: the HVAC housing consists of two halves joined by metal clips and screws around the perimeter. Remove all screws (usually 8-12 TORX T20 screws) and carefully release the metal clips around the perimeter (they are tight and will take some force). Separate the housing into two halves. The heater core is located in the front part of the housing, usually in a plastic cassette.
  10. Remove the old heater core: carefully pull the old heater core out of the cassette (it may be held by plastic brackets or screws). Inspect the housing for cracks, dirt, and leaves. Wipe the inside of the housing with a dry cloth and remove debris. Check the condition of the seals and blend doors, and replace them if necessary.
  11. Install the new heater core: place the new heater core in the cassette and secure it with the brackets or screws. Make sure the core's pipes line up exactly with the openings in the housing that lead to the engine compartment.
  12. Assemble the climate control housing: join the two halves of the housing, checking that they are aligned correctly. Install all the screws around the perimeter and snap the metal clips into place. Reconnect the blend door actuator connectors.
  13. Reinstall the HVAC housing: secure the housing to the body with the screws. In the engine compartment, slide the heater hoses onto the pipes of the new heater core and tighten the clamps (tighten the clamps moderately, enough to seal without cutting the rubber).
  14. Reassemble the interior: install the metal beam and tighten all the mounting bolts to the body. Install the upper dashboard section, center console, climate control panel, and vents, reconnecting all connectors. Raise the steering column back into place and tighten the mounting bolts. Install the trim panels.
  15. Refill the coolant: prepare a 1:1 mixture of MB 325.0 coolant and distilled water (or use pre-mixed coolant). Pour the coolant into the expansion tank up to the MAX mark. Reconnect the battery negative terminal.
  16. Bleed the cooling system (remove air pockets): start the engine, set the heater to maximum temperature and minimum fan speed. Let the engine warm up to operating temperature at idle (about 10 minutes). Raise the engine speed to 2000-2500 rpm several times to help air escape from the system. Watch the level in the expansion tank: it will drop as air escapes, so top it up to MAX. Repeat the procedure 2-3 times until the level stabilizes. Check that hot air is coming from the vents (a sign that there are no air pockets in the heater core).
  17. Check for leaks: after bleeding, shut off the engine, let it cool, and inspect all the heater hose connections in the engine compartment and under the dashboard (if accessible) for leaks. Check the coolant level in the expansion tank the next day. If it has dropped, top it up and bleed the system again.

Common mistakes and warnings

  • This job involves removing airbag components and electronics, so always disconnect the battery and wait 15 minutes before starting. Do not use metal tools near airbag connectors. The cooling system is under pressure, so open the expansion tank cap only when the engine is cold. Air pockets in the cooling system can cause the engine to overheat, so bleed the system thoroughly after replacing the heater core. If you have no experience working with electronics and airbags, take the car to a repair shop, because a mistake can cause the airbags to deploy or fail.
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