I am planning to replace heater hoses and hoses to the windshield heat exchanger before they break. It looks like I will need to remove the extra firewall between the engine and the conventional firewall. How is it removed? I do have the CD service manual. Could anyone point out which section deals with the firewall? Or is there a way to remove and replace heater hoses without removing the extra firewall? Thanks.
85 300sd.

There is a removable section of that firewall....right in the middle. I believe two screws will allow you to lift it off. No big issue. I'd definitely recommend it for any work between the two firewalls.

I think it is four bolts. Something like 6mm heads on them. Two are visible at the top of the panel and two are at the bottom. I took mine off when I was having Monovalve leaking issues and never put it back on. It became a one of these days things to do...

Here is what I did:

1) remove the firewall panel

2) remove the clamps on the three hoses going into the passenger compartment

3) remove the clamp from the hose leading from the metal pipe to the aux water pump

4) remove the electrical connectors from the pump and the monovalve.

5) remove the screws holding the monovalve and the pump in place.

6) remove the pump/valve/hoses assembly. The hose going to the pump runs through a small hole in the extra fw. It is a pain to get it to go through that hole.

7) replace all the hoses off the car, rebuilding the pump/valve/hoses assembly

8) replace the assembly, forcing that damn hose through that damn hole!

put it all back together.

Make sure that you replace the small hose going from the pump to the valve... I did not do that the first time of course it blew immediately afterwards...

__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf ‘86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad

I'd put that back on, a lot of water and junk can get in there if its not in place. They made it that way for a reason....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

I know... I will probably get to it this weekend now that I have been reminded of it

__________________
"I have no convictions ... I blow with the wind, and the prevailing wind happens to be from Vichy"

Current
Monika '74 450 SL
BrownHilda '79 280SL
FoxyCleopatra '99 Chevy Suburban
Scarlett 2014 Jeep Cherokee
Krystal 2004 Volvo S60
Gone
'74 Jeep CJ5
'97 Jeep ZJ Laredo
Rudolf ‘86 300SDL
Bruno '81 300SD
Fritzi '84 BMW
'92 Subaru
'96 Impala SS
'71 Buick GS conv
'67 GTO conv
'63 Corvair conv
'57 Nomad

ya all just HAD to go and mention the heater hoses there didn't you... NOW you know what will start leaking tonight right?
Roy, are you listening? send me a set of hoses for here please...

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

I have to pull them all out this weekend to replace my aux water pump.... Not looking forward to it, but I am looking forward to better heat in the car....hopefully my repairs/improvements will give me back my heat!

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)