Heater box removal

Bmachine

Bmachine

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OK, I’ve now spent seemingly several hours searching the forum for info on removing the big black heater box behind the AC evaporator. There are several really good threads on removing the evaporator, but for some reason I couldn’t find any info on removing the big black box behind it. I suspect it is buried inside some other rebuild threads. But, for example @Markos deconstruction thread only details the evaporator removal.

Does anyone know where I could find info on that next step? @HB Chris, is it in your b35 thread somewhere?

Thank you
 
Seems like you could've already been halfway done removing it, along with a nice youtube video for the rest of us. ;)

If you find info buried in another thread you can add a tag for future reference.
 
Hi @Bmachine,

Sorry I missed that one.

Keep the heater controls connected to the box. Don’t mess with any of the cables at all. Loosen the hose clams on the defroster ducts and slip them off.

IIRC, the perimeter of the box has screws that secure it to the firewall, accessible from the cabin. Once the screws are out you need to give the box a good tug. It is somewhat adhered fo the firewall with a rectangular seal, so it shouldn’t just fall out when you remove the screws.
 
dang said:
Seems like you could've already been halfway done removing it, along with a nice youtube video for the rest of us. ;)
Click to expand...
“I don’t want to reinvent the wheel. “
“But by now you could have figured out how to do it.”
”But I would have probably broken half the delicate parts that didn’t even need to be touched to begin with. “
"None of the search words I am trying are getting me anywhere."
“But you haven’t made any progress in two hours.”
“But there HAS to be someone who has written something about it”
“Crap, I promised to make dinner tonight and it’s almost time!”
“Aaaaaargh!”
 
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Markos said:
Ahh, are there studs on the firewall?
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I am only halfway through, but if I’m doing it right, they are on the upper part of the firewall. The part that angles towards the inside of the cabin. Hiding behind the black plastic ducting that you have to remove first.

The upper one is a real pain to get to because there is an electrical wire going into the box right under it. So you can’t slide a socket in there. And this is supposed to be the easy side!

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Crap! After laboring to get these four bolts out and then having to pretty much chisel the box out of it’s glued gasket onto the firewall, the whole thing still wouldn’t come out. And then the coin finally dropped! Before you remove the box, you obviously need to disconnect the inlet water hoses! Duh! What a pain. I need to be able to run the motor tomorrow to take it down the driveway and onto the tow truck to bring it to the paint shop. I don’t have time to drain the coolant and all that and then bleed the system with all the other stuff that needs prepping!

Plan B. Quick! What’s my Plan B?
Uhhhhh, thinking, thinking, thinking…
 
For the sale of others looking this up later, it is very helpful to have a set of ratcheting box wrenches. Works well for situations like this.

@Bmachine,

You can use vise grips to clamp the hoses. I have an assortment of rubber stoppers for stuff like this also. You can find them in the hardware (nuts and bolts) section at ace hardware.

Bmachine said:
Crap! After laboring to get these four bolts out and then having to pretty much chisel the box out of it’s glued gasket onto the firewall, the whole thing still wouldn’t come out. And then the coin finally dropped! Before you remove the box, you obviously need to disconnect the inlet water hoses! Duh! What a pain. I need to be able to run the motor tomorrow to take it down the driveway and onto the tow truck to bring it to the paint shop. I don’t have time to drain the coolant and all that and then bleed the system with all the other stuff that needs prepping!

Plan B. Quick! What’s my Plan B?
Uhhhhh, thinking, thinking, thinking…
Click to expand...
 
Probably a dumb question here, but I forgot what kind of pressure the coolant reaches at the heater inlet level. Can you still run the engine for a couple of minutes (before the thermostat opens for example) once you have those rubber plugs in ?
 
Come to think of it, is there any reason I could not put some kind of a fitting between the two ends? A simple bypass of the heater core?

Not that I would have any time to go and look for one at this point but…
 
A half-inch pipe nipple should work as a bypass splice. The system would get to about 15 PSI before the radiator cap would let some pressure off if it were idling for long enough. And you'll end up with a little air in the system but nothing that wouldn't work its way out. Do you have any really, really big bolts lying around? Again, 5/8" in diameter or thereabouts? Plug the hoses with those and squeeze the hose clamps down really good.

You're almost there! You'll be glad you had a deadline when the work is done!
 
Blinkling said:
A half-inch pipe nipple should work as a bypass splice. The system would get to about 15 PSI before the radiator cap would let some pressure off if it were idling for long enough. And you'll end up with a little air in the system but nothing that wouldn't work its way out. Do you have any really, really big bolts lying around? Again, 5/8" in diameter or thereabouts? Plug the hoses with those and squeeze the hose clamps down really good.

You're almost there! You'll be glad you had a deadline when the work is done!
Click to expand...
Big bolts! Great idea! Will have a look early tomorrow morning before the tow truck comes. I’m on dinner duty tonight... :-(
 
You can completely bypass the heater core. Just use a flexible heater hose on the engine side of the firewall. I did this in my VW commuter for about 7 years.
 
Just saw this now. The BMW blue book has all the steps for heater box removal. Just must flip to different sections to progress from under dash panel removal, to demister hoses, to side panels to selector cover, to ventilation grill, etc. BTW, not that it helps you now, but first thing they say to do is drain some coolant and detach heater hoses at firewall. :rolleyes: My point is, I often forget to consult the Blue book before taking on a project. If I read that first, then all the threads on this Forum about how to address any obstacles, are pure gold!
BTW, drove my Coupe for about 2 years with heater hoses disconnected. Just a messy install because, in my case, carb had to come off for access, then some rerouting of really flexible hose. Carb back on, refill and bleed, and bleed and bleed. Best of luck, Bo!
 
In case someone else needs to do this, here is a step by step of the process, thanks in great part to all who contributed to this thread here above.

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 the evaporator. Remove the two slotted screws holding the control panel fascia to the lever assembly, it goes you more room to pivot this out of the way.
  • 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 10 mm nuts. In order to free the box up, you may need to pry it with a chisel. Be sure to pry under the area with the metal bracket and not under an unsupported section of black plastic. It would break easily. 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 but it will eventually come out.

PS: AC evaporator removal:

AC Box Removal

Hello everyone, This is a little embarrassing, I'm trying to remove the AC box in my car but it won't budge. Four Phillips screws have been removed, two in the back and two in the front. Also, two 8 mm bolts from the front and the AC lines have been disconnected. Is there anything that I'm...
e9coupe.com e9coupe.com
 
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It is also easier to remove the control panel cover from the levers, only two slotted screws are removed. I am going to edit the two nuts to four on the firewall.
 
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