Hi Everyone,

I tried to turn the heater on the other day, and absolutely nothing happened. No fan sound, nothing!! (as I'm in LA, it wasn't necessary to turn on the heat, so I never tried it). I figured its something electrical, but I've been doing the regular new owner type repairs, valve adjustment, fuel filter change, diesel purge, etc, etc, and I've noticed that there are disconnected hoses all over the place. So I figured that I should take care of the mechanical part of the heater, then worry about the eletrical later.

That being said, I've got a lot of disconnected hoses, and hoses that go no where, so I have no idea where to begin. There's a hard rubber hose that is open right in the middle of the firewall just below the throttle bushing that has no hose attached. There's also a hose that goes from the aux water pump to the water pump on the engine (which is located passenger side near the headlight assembly), but it's not connected to anything. I haven't checked under the passenger side dash yet, so I don't know what's there or what's not. I don't know the plumbing of the heater, so I have no idea where those hoses go. All I know is that there's an auxillary water pump, and a mono valve (which are connected btw), and some disconnected hoses. That's all I've figured out.

Finally, here's my question or questions rather. Where does it get it's heat from?? It has to get it from the engine block someplace, right?? Is there someplace online that has a 'plumbing' diagram of the whole heater system??

I understand this will probably take a long time to fix. I'm not fixing it right away, I just want to get prepared and plan ahead so I know what I'm getting into and I know what to expect.

Thanks in advanced!!!

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1984 300D Turbo -- Just bought it June 2007 for only $650. My first Mercedes-Benz and my first Diesel.
1964 VW Karmann Ghia -- in parts Long overdue for a restore.
2006 Audi A3 -- Great car, but I hate the car payments!!

The hard rubber hose, would that be a vacuum line? Small in diameter. One of them, black in color, is a vent, usually inside, that does not hook up to anything. Otherwise a pic will help in determining other aspects. The heater itself, I believe, is a core type affair that resembles a radiator, located in the dash somewhere, that hot water passes through, and a fan blows across it, hot air delivered. It is sealed, so it will look like a black box.

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83 SD

84 CD

Sorry took so long to reply. I had camera issues, and I haven't had much time working on my car.

Anyway, here are the links to my missing hoses.

http://topherdotcom.com/images/missing_hoses1.jpg
-- Bottom right corner of the pic, below the throttle bushing, there's a hose that goes nowhere. Where does that go to?

http://topherdotcom.com/images/missing_hoses2.jpg
-- Top of photo is the water pump, to the left is the turbo, and bottom (not picured) is the aux pump. The hose on the left is connected to the pump housing (top of hose) and the bottom is plugged. The hose on the right is coming from the aux pump and that goes no where. Again, where do these go?

http://topherdotcom.com/images/missing_hoses3.jpg
-- Hose in question is between the battery and the mono valve. That comes from firewall to ????? Also noticed the top of the monovalve and it appears like the wires have been cut. Where does that hook up to?

The 4th hose (no pic, totally forgot about it), is located on the driver side in the engine block and goes back to firewall and makes a left turn. That hose is also plugged. I'm assuming it goes to the heater core??

Also, would there be any reason as to why the PO disconnected everything?? Any insight to this is much appreciated.

BTW, I plan to do a citrus flush soon. The PO used the green stuff. Should I wait till I figure out the heater plumbing, or go ahead and flush??

Thanks!! and sorry for the million questions

__________________
1984 300D Turbo -- Just bought it June 2007 for only $650. My first Mercedes-Benz and my first Diesel.
1964 VW Karmann Ghia -- in parts Long overdue for a restore.
2006 Audi A3 -- Great car, but I hate the car payments!!

First pic is the vent, goes nowhere, does not hook up to anything.
Second pic, I cannot tell, still not sure if you're referring to a heater hose, or vac hose. May be EGR related.
Third pic is a cowl drain, goes down.

__________________
83 SD

84 CD

Im sorry my car is out of comission so everything I am saying is from memory. First of all the heater setup is as follows. The auxillary water pump draws hot water from the thermostat housing, then it lifts it to the mono valve which obviously opens when the CCU is asking for heat. The outlet from the mono valve then connects to whatever hard line is the inlet to the heater core. Now I really haven't looked yet but from what I was thinking there might be dual heater cores in these cars because if I remember correctly the outlet on the mono valve feeds into the firewall on two spots, so naturally there are 2 outleys that eventually feed back into the engine on the drivers side. I could be completely wrong about all this since my car is not infront of me. I will tell you exactly where everything goes when I can. Also the best guess is that the PO disconnected all these lines because a heater core ruptured. Otherwise they hated heat. I don't think toomany MBZ understood what hoses you were referring to. But yes the large black fishmouth thing is just a drain.

I think you are trying to go the wrong way on a one-way street. (Which is not to say that the thermostat housing has any involvement whatsoever.)

I have a 1975 280C. Heated antifreeze moves through the hoses, but no fan, no fan=a little bit of radiated heat. I am still looking into how to get the fan running. Even hooked up the squirrel fan direct to a power source and could not get air to circulate past the heat radiator. So I would look into seeing if the heater fan is working.

If the fan does not turn with aid of a stick, does that mean that it is frozen, and how can one access the fan?

It's hard for me to interpret your pictures, but here's what I think. I don't see any cut wires on the monovalve.
I'm betting the PO had a leaking heater core and just disconnected the heater hoses instead of replacing it. This would account for the disconnected hoses where the coolant leaves and returns to the block.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The reason why i posted in the first place was to know the plumbing of the heater system in the engine compartment. I just need something like "hip bone is connected to thigh bone, the thigh bone is connected to the......." you know the rest.

Anyway, can anyone tell me what connects to what?? Or can direct me to someplace that has a diagram??

Thanks!!

__________________
1984 300D Turbo -- Just bought it June 2007 for only $650. My first Mercedes-Benz and my first Diesel.
1964 VW Karmann Ghia -- in parts Long overdue for a restore.
2006 Audi A3 -- Great car, but I hate the car payments!!