If you seriously are considering this this procedure, please read through this from start to end. Total time is somewhere between 8 and 16 hours of work.
oldpoopie on TDICLUB (this thread was crucial)
Vortexpert (this thread helped as well)
tperretta (here and on TDICLUB)
VgRt6 for the writeups on interior removal
tatge for the writeup on steering wheel removal
CAUTION: Before you get started, be warned that this procedure takes ALOT of time and ALOT of space! It is technically possible to do this in a driveway, but you will need someplace outside the car to store at the very least your dashboard. Also be reminded that we are removing the cowl, and your car is no longer watertight! Rain can run right through your blower motor into the cabin.
BIG SAFETY NOTE: You will be working in close proximity to your airbags in their virgin, unprotected states. SEVERE injury or DEATH could result from accidental static discharges. If you are so inclined, run a wire from someplace like your muffler to a cast iron water pipe or other suitable ground. Otherwise, pay close attention to what clothes you are wearing and where your hands and tools are.
Climatronic or Cable actuated? (AKA the SPLIT or NO SPLIT HVAC CASE PROBLEM): Models equipped with Climatronic do not have a central split in the plastic HVAC case between the heater core and AC condenser. If this is the case, you will need to discharge the AC system and, of course, recharge it when you are complete. Local laws typically do not permit discharge into the atmosphere, so you will want to have this done at a shop before you start. See step 15 for more details.
PARTS AND TOOLS:
Heater Core: 1J1 819 031 B (Note: make SURE it is the B revision) and a firewall seal if they have it (I do not know the PN)
T55 Torx bit or 12 point bit for steering wheel
T20, T25, and T30 torx bits or screwdrivers
Phillips and flathead screwdrivers in various sizes
10 and 13 mm standard sockets
10 mm deep socket for studs
Recommended: Threadlocker, RTV silicone, Dynamat (or similar) sound deadener.
1) Remove the dashboard. This part should take you four hours or so, and represents most of the parts removed from the car.
The next few steps we will be freeing the large steel crossmember. It does not actually have to move far, but it does have to move at least an inch to get ductwork out of the way.
2) Free the steering column. First remove the wires from the ignition switch (left and right).
To prevent damage to the column, fashion yourself a retainer from wire to connect the column loosely to the crossmember. I used the wire handle from a gallon paint can, which I then secured to the screw that attaches the dash behind the instrument cluster. Now, remove the two 13mm bolts holding the column to the crossmember. They are under the column.
3) Remove the seventh "mystery bolt" reinforcing the steering column/crossmember/firewall area. To do this, remove the wiper arms and the cowling under them (it just pops into the channel attached to the windshield). Now, remove the wiper motor assembly (three 10mm bolts). Behind there is the mystery bolt. It is 13mm, same size as the four holding the crossmember to the door sills.
4) Loosen the crossmember. On each side, remove the bottom of the two 13mm bolts holding the crossmember to the door sill. Loosen the top one. Note that the member has a retaining pin from the sill it sits on. This is good, because these pins are the only thing keeping the dash lined up properly. Now, remove the two bolts on the bar connecting the crossmember to the windshield area of the firewall. Now we can move the crossmember when we need it by removing one or the other bolt, without needing to risk the bar falling on our laps and destroying wiring looms or relays.
5) Remove the crossmember struts. These are what connect the crossmember to the center tunnel, and surround the radio cage. Removal is necessary later on, you will see. Mark or note which side each one goes. Also, note someplace (either in a notebook or with a picture) how the bowden cables and wire looms cross the left hand strut. This is important later.
6) Free the HVAC box from the firewall. Looking at the Bentley manual, you can see that the heater core, AC core, blower motor, and all flaps and valves, are attached to one big assembly. They do not show you how it is attached to the car however! Thanks! We need to free it up to split it into two pieces for heater core replacement. It is attached by four studs that penetrate the firewall. Two studs are below the heater core passthrough, and the other two are above and below the AC core passthrough, where the expansion valve is located.
First, remove the nuts below the heater core. These are behind U-shaped flaps cut into the heat shield. Note there is a third cut which has the drain for the AC system.
Next, remove the nuts above and below the expansion valve. I had to remove the insulation cover for the expansion valve. I also had to tear the fiber mat to get at these, but you will feel strangely satisfied with destroying something at this point so have at
The next few steps, we will be removing pieces-parts attached to the HVAC box.
7) Remove the center-dash vent from the front. This is in two parts: an upper and a lower. The upper is friction-fit to the lower, and kinda clips into the crossmember. The lower is attached with two silver phillips screws, one on each side. Remove them and pull the lower straight back.
8) Remove the center defroster vent from behind the crossmember. This requires removing the passenger side bolt we left on earlier (leave the driver's side one loose but on), supporting the passenger airbag up with your knee, pulling hard backwards on the crossmember, and with your third hand shimmying the vent out the passenger side.
9) Remove the footwell vent manifold. It appears there are multiple versions of this duct (the Bentley has a picture which does not match mine) but it basically clips in to the heater box. Once it is off, remove the rubber connect at the bottom of the main manifold, connecting to the lower air ducts.
If you have a later model, with the larger glovebox and no passenger side knee area energy absorber (you will know if you have one), skip to step 11. Otherwise:
10) Remove the passenger side knee area energy absorber. It is located such that we will not be able to get the HVAC box out far enough to get the heater core interconnects into the cabin. We need the bracket off too, so just remove the three small bolts from where they connect the bracket to the crossmember. Either set it aside, or just recycle the thing and start looking for a large style glovebox. It is a solid hunk of aluminum after all!
11) Drain coolant. Search for a writeup if you need help (there are at least two), but the main drain is located at the driver's side of the radiator.
12) Remove the two quick-connects on the engine side of the firewall for the heater core.
Read step 13. It is not required, but you may want to revisit this step if you get stuck on the next step.
13) Back in the cabin, it would help to make a little space around the HVAC box. If you have been lucky, the sound insulation mat is in good condition. If you are like me, and you had a mystery leak in your windshield for several years, it is looking a little old and moldy. My choice was to just rip the entire upper insulation mat out. Alternatively, you can carefully work around it. Your choice.
The blower assembly also has a passenger-facing sound insulating mat and a lower foam kick piece. Both were held on with zipties, which annoy me. I cut them off. It is possible to work around them.
14) Now we need pull the HVAC box back from the firewall just enough so that the heater core interconnects are inside the cabin. Pull primarily from the heater side. The AC side will move a bit, but not much: it is constrained by the steel lines in the engine compartment.
15a) See the image below. Do you see these spring clips? If not, you probably have Climatronic, and you should skip to step 15b.
If you do see the spring clips, you can save a bunch of time. There are six of these spring steel clips holding what I will call the heater box to the HVAC box. In the picture above you can see three, there are also two on the back and one on the bottom. We are going to remove these and pull the heater box out the middle of the dash, wires and all. Skip to step 16.
15b) If you do not have the spring clips (ie: you have Climatronic), verify that you have depressurized the AC system and disconnect the AC condenser lines which are on the engine side of the firewall. Then, you should be able to maneuver the entire box far enough out to see the top of the heater core. I would actually love to hear from people who have done this, and can host a picture of what it should look like for posterity.
16) The heater core is attached by two screws to the top of the heater box (or heater side of the box). Voila!
Congratulations! You just did this to your car!
If you are reading this and just considering doing this: if just seeing this picture gives you heart palpitations you should definitely NOT undertake this procedure and call a professional.
1) We need some gaskets for the core swap. Reuse or replace the gasket between the heater core and firewall. There is a second gasket which seems to not be replaceable (and was not on the new part) which seals the core to the heater box. I used RTV.
2) Put the HVAC box back together. This is one unit if you have Climatronic, and just the heater box if you are cable-actuated. For the cable folks, the six spring clips just snap into place. The hardest one to get to is on the top in the back, but it is easily reached from the bottom. For all models, once together push it into place so that the heater core to firewall gasket is seated, the AC drain is seated, and all four studs are fully penetrating the firewall.
3) Reattach the HVAC box to the firewall. Four nuts. Torque is not listed anywhere I can see, but assume under 10 Nm and use blue threadlocker.
4) If you did step 13 above and ripped the upper sound insulation pad out, you may want to lay a new pad. I used sound-deadening pad available at the local auto parts store. I needed five 10-inch square pads to get the top of the unit-body below the windshield. You also have to remove the funky bar connecting the crossmember to up by the windshield. Assume 25 Nm for this bolt and use blue threadlocker.
5) Reattach all the snergely ducts to your heater box. Put the rubber interconnect over the lower manifold. Then, put the lower manifold back in as it came out. The rubber connect to the rear footwell slides into place. The front box (center vents) screws into place on the left and right. I used a bunch of RTV on these connections in the hope it might kill my dash rattling, but you can skip this detail. The center defrost vent requires you to loosen the crossmember on the passenger side (see above).
6) Reattach the crossmember (two bolts per side, one on the firewall). Torque is 25 Nm, and use blue threadlocker for good measure.
7) Reattach the lower crossmember-tunnel struts (three crossmember bolts per side). Note how the bowden cables for the duct flaps cross the driver's side strut. Attach the tunnel bolt first, then the top two. For the top strut (between the windshield and steering area) has two T30 bolts. No torque is listed, but get them hand tight and use threadlocker.
8) Reattach your wiper motor and wiper arms. Torque for the motor mounts is 10 Nm, and the arms are ? Nm.
9) Reattach the cowling and cowl molding.
10) Reattach the steering column. Torque is ? Nm. Finish by reconnecting the ignition switch and reattaching the wiring looms to the column.
11) The reverse of the dashboard removal. All the way back to the rear cupholder!
12) If your HVAC case did not have a central split (ie: you did step 15b above) you need to recharge your AC system. Do it now or later, but don't forget. You will miss it that first hot day of the year.
13) Power up and test. PLEASE make sure NO ONE is in the passenger compartment when you connect the battery, just in case the airbag controller decided to go full retard on you. Test all functions: heat, cold, vent combinations, vent lights, stalk functions (you can test the cruise control when you get a chance).
You are done!
(The Bentley manual has all the torques. Help feed those nice dudes and buy the manual.)
Modified by darisd at 9:38 PM 12-12-2009