I will soon be doing cooling system maint on my 1991 MB 300-SEL - M103 engine. Upper/lower hoses - hose from expansion tank to radiator and one L-shaped heater hose - tstat - coolant - expansion tank cap - etc. will all be replaced. Most hoses under the hood that are easily accessible will be replaced.

I noticed one coolant hose on the drivers side that comes off a metal pipe just below and to the right of the oil filter. It goes back thru the false firewall. It then takes a left turn(facing firewall). This hose - roughly 1" OD has a smaller hose that branches off of it at the end that's behind the firewall.

The part number for this hose is 126 832 38 94 - there is one on ebay if you care to see what it looks like. Search there for the part number.

Mine is not leaking, but it is original(26 yrs. old) and I started thinking about how I would go about replacing it if I ever needed to. There are a number of other hoses behind the false firewall - monovalve/heater core stuff I suspect.
I found a diagram of a W126 false firewall. Looks to me like the FFW is sectionalized. Item #17 in this diagram could conceivably come off and provide some access to hoses behind the firewall. Others components may also need removal.

Curious if anyone has removed sections of the FFW to replace hoses or other components back there?

Update - this site won't allow me to upload the diagram. Maybe some of you are familiar with this and can comment using your experience with this.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

I have no real idea but my gut feeling is the MB engineers made it about as easy as possible to work on these vehicles. So my guess is that you are correct and that there is a fairly simple way to remove it - either in parts or all in one.

Have no idea about the current vehicles but in the 70-90 years I suspect they all were designed with the mechanic in mind. I have an '81 300SD and everything on it is a dream to repair; you can basically get to everything.