Warning: These are just step by step notes without photos. Apologies for that. But I wrote them down when I took mine out so I figure this might be better than nothing for someone who is about to embark on this "challenging" adventure.
At the risk of stating the obvious, in order to even get to this point, you obviously must first remove the center console and, if you have AC, the evaporator. @Markos wrote very good instructions for that here:
https://e9coupe.com/forum/threads/deconstruction-thread-how-to-part-out-an-e9.21251/page-7
Steps to remove the heater box
At the risk of stating the obvious, in order to even get to this point, you obviously must first remove the center console and, if you have AC, the evaporator. @Markos wrote very good instructions for that here:
https://e9coupe.com/forum/threads/deconstruction-thread-how-to-part-out-an-e9.21251/page-7
Steps to remove the heater box
- In the engine bay:
- Drain the coolant at the radiator
- Loosen the clamps for the two hoses that are going into the heater.
- Remove the two hoses from the heater inlet. Be careful as some coolant will start splashing from there
- Although not strictly necessary, It will make things easier if you remove the heater fan.
- Inside the car:
- Best is to remove the seats for easier access
- Get a camping mattress or something to protect your body from all appendages on the floor
- Get a good wide beam flashlight
- Remove everything on top of the tranny tunnel: attaching plates for the AC, carpet, as much insulation as possible. You need to make maximum room available under the heater box in order to slide it out without damaging the captive studs in the angled firewall
- Disconnect all electrical connections to the heater
- Loosen the clamps for the two black plastic duct hoses on either side of the heater
- Remove those two ducts
- There are four 10 mm nuts that secure the whole unit to the top part of the firewall. The part that angles towards the inside of the car. Use a short 10 mm socket with a long wobbly extension to remove all of them. I found that the hardest one was the upper right side one because there is an electrical wire going into the heater body right where you want to put your socket. Ratcheting box end wrench may help.
- Do not remove any of the mechanical heater cables / actuators. They will come out with the heater box
- The whole box is by now probably glued to the firewall through the big rectangular gasket that has been compressed into a sticky goo by the four M6 10 mm head bolts. In order to free the box up, you may need to slide a chisel under the metal bracket section of the evaporator in the firewall. Easiest to do that from the left side.
- Once you have it freed up from the firewall you have to wiggle it out with the accompanying rectangular heater baffle and heater controls. It takes a bit of fiddling.
- WARNING: when you “wiggle the whole thing out” be very careful not to let the metal plates that the four M6 nuts were tied against scrape on the captive studs from the firewall on their way out. I discovered that it is very easy to damage their threads that way. And since they are captive, it is very difficult to repair them
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