Here is a list of coolant hose part numbers I've compiled for the 1981-1985 w123 300D, 300CD 300TD 617 diesel models. Includes 1981 N/A and Turbo version with ACCIII climate control. Include some of 1985 California version which has a difference in the Aux pump hoses and I believe monovalve hoses and expansion tank main hose.

Radiator-
Radiator lower: 123 501 18 82
Radiator upper: 123 501 00 82
Expansion tank main hose: 123 501 21 82
Expansion tank secondary hose: bulk hose with 6mm inner diameter and 9 mm outer diameter

Heater hoses (numbers correspond to the numbers on the attached pic.) -

1.) Auxiliary pump to feed pipe: 123 832 94 94........California 1985 version "Z" or "S" hose. Might be unavailable but possible substitute: 201 832 13 94
2.) Auxiliary pump to engine: 123 832 91 94............California 1985 version "J" hose: 123 832 50 93
3.) Heater Core left to feed pipe: 123 832 89 94
4.) Engine to heater feed pipe: 123 832 84 94
5.) Heater core right to feed pipe: 123 832 88 94
6.) Heater core center to feed pipe: 123 832 87 94
7.) Monovalve to feed pipe: 123 832 90 94
8.) Monovalve to auxilary pump feed pipe: 123 832 93 94


(Picture taken from google search)






Any other w123 models, feel free to post the part numbers and corresponding pictures if you have them..



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1983 123.133 California
- GreaseCar Veg System

Thank you for the informative post! As I look at those hoses, I'm guessing if you had to, hoses 1 and 2 would be easily replaceable with standard heater hose if necessary; the others...with all the bends? Not so much.

Number two would not likely work with standard heater hose, as it is flared at one end. Apparently silicone hose is stretchy enough to slip over the larger fitting at the block though.
Related: i pulled the hoses from monovalve to aux pump to block last night. Found a quite a bit of corrosion on the outside of the metal pipe that runs between them under the old hoses. Havent decided if I will use POR-15 or standard spraypaint to coat the outside of the pipe after I clean off the corrosion yet. I would suggest planning to replace any of the hoses you disconnect if they are original to the car.

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'85 300D - federal spec, built in late 84. 85 300D Complete AC System Rebuild

For the line between the aux water pump and the monovalve feed pipe (#1 above) the two sides of the hose are probably slightly different diameters. The aux water pump is roughly 1/2", and the monovalve feed pipe is roughly 5/8". You might be able to find some bulk hose that would work, but I decided to just order the OE MB part.

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'85 300D - federal spec, built in late 84. 85 300D Complete AC System Rebuild

Thanks, just so I'm sure on this, the Auxiliary pump only runs after you shut off the car and I don't need it to feed the heater correct?
Greg

Auxiliary pump runs at low engine speeds, but many people have deleted it with no ill effects. It's supposed to run when you're sitting in stop and go traffic or idling for a extended time, but when it breaks it slows coolant flow through it.

That's just what I've read from others on this forum.

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Milan Brown 1979 240D, rebuilt OM617.952 turbo diesel, rebuilt 722.315 transmission - engine spun a rod bearing

1979 300SD, ~90k original miles, all stock

It is recommended that the auxiliary pump be fused with an inline 2 amp fuse. If the pump fails it can also take out the CC push button unit.

How does the ACC system receive information about engine speed?

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When cryptography is outlawed, bayl bhgynjf jvyy unir cevinpl.

This is a very helpful thread, *however*, there is one crucial hose that is missing. People (non-professional technicians) typically discover it *after* they've drained the cooling system and they suddenly realize that they are in trouble since they have no such hose.

I am referring to the short (2"?) hose that is situated between the thermostat housing's bottom (vertical, not diagonal) port and the port adjacent to the water pump. See the attached pics. 1-3.

So, what to do when one seeks to replace this hose? Well, I believe (but cannot prove) that M-B does not sell the hose. Thus, one uses a piece of 1-5/8" hose (see attached pic. 4). When cutting the length needed, seek to replicate the length as best you can - there is not a lot of acceptable latitude to deviate.

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Blew my SLS High pressure line a couple weeks ago. got around to replacing it today... took it for a test drive, and guess what, the 2" hose failed! I mean totally came apart! I guess the fluid from the sls had softened it up? Anyways, working on fixing it right now....

Do we have a part number of the metal hose that bolts under the battery tray? This metal pipe has hoses on each end of it. One hose hits the mono valve on the end nearest the battery tray, the other hose that attaches to it hits the aux water pump. Thanks in advance to anyone with that part number.

I've used a bulk 42mm hose in the past. Perhaps 1 5/8 might fit a bit tighter. I also thought about trying a 41mm hose.

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1983 123.133 California
- GreaseCar Veg System

You are referring to the metal line between hose #1 and #8 in my above post.

I found two part numbers :123-830-83-15 and 123-830-20-16

I am not clear which is correct for what application. If I had to guess, 123-830-83-15 would be for the standard 617 models and 123-830-20-16 would be for the 1985 California 617 models.

Pelican has them both BTW

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1983 123.133 California
- GreaseCar Veg System

I have some part numbers to contribute for anyone looking to replace those heater hoses that are no longer available. I measured the inner diameters and found some molded hoses from Napa that resembled ours. You'll need to cut each of these down, but after doing so, I was very pleased with how well they fit on.


Replacement for MB Hose 123-832-94-94 (#1 in OP's photo)
NBH 11935 - Molded Heater Hose 11/16" x 11/16" x 11 31/32"

Replacement for MB Hose 123-832-89-94 (#3 in OP's photo)
NBH 11600 - (Molded Heater Hose 3/4" x 3/4" x 11")

Replacement for MB Hose 123-832-87-94 (#6 in OP's photo)
NBH 13398 - CURVED HOSE

Replacement for MB Hose 123-832-93-94 (#8 in OP's photo)
NBH 7713 - Molded Coolant Hose 3/4" x 3/4" x 5 11/16"


ALSO - I found the appropriately sized (42mm ID) short coolant bypass hose from a company called Performance Products. SKU: 236907

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thats a great resource! thanks for posting it.
I was working on my '79 and checking a possible coolant leak, all hoses ok then I got to looking in the passengers side and Oh I think I have a leak from the heater core
dammit I guess its time to either sell the car or replace the dash with the new one I have stored away and keep her.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!