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Old 12-10-2011, 01:33 PM
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Coolant flow on 1978 300D for heater and servo?

Anyone have a diagram? I'm getting page not found on my factory manual CD. Apparently it didn't come with coolant flow for this from heater core to servo etc. Didn't see it in the climate control manual. Did'nt see it searching.

I'm trying to figure out how to bypass coolant at leaking servo and understand the coolant flow. The posts on bypassing servo that i have found don't get too descriptive about what lines go where and what to hook up.

Here are some questions someone might help me out with.

1) in this pic: Which is the inlet and outlet to the heater core? I'm thinking the big one is the inlet. Which means that is where i need to hook up the outlet to the pump.

2) What are there two pipes coming out of firewall that join togeter for return from heater core? (assuming that is the return from heater core)

3) If im right about the return and the supply to heater core, that means i have hook up the four lines at the servo on diagonals -- that is in this fasion: The line from the aux water pump for heater goes to heater core inlet which is diagonally across from it on the servo. And the return comes into the servo diagonal from the return to water pump line .

Don't you need to T the return to water pump and supply line from heater pump together as well though for when you have the water flow to the heater core blocked off with the manual valve?

Any help is much appreciated .

Attached Thumbnails
Coolant flow on 1978 300D  for heater and servo?-photo-1-4.jpg   Coolant flow on 1978 300D  for heater and servo?-photo-2-4.jpg  
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Last edited by biopete; 12-10-2011 at 01:34 PM. Reason: forgot pics
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Old 12-10-2011, 02:29 PM
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So i found this . early W123 servo bypass described/pics

The pics show there is no need for a T from the coolant supply to heater core to bypass. I guess that there is a bypass built in already. But it doesn't specify what hose is the in for heater core and what hose is the out.

Everyone seems to know this but me it seems I think i'm right though, hook em up diagonally?
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Old 12-10-2011, 02:33 PM
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I think i know why: I'm an idiot. So of course just the one pipe is the inlet otherwise the coolant would flow to various places and not directly into the heater core.

I"m going with that. Unless anyone corrects me Thanks.
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Old 12-12-2011, 04:02 PM
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Quote:
Originally Posted by biopete View Post
So i found this . early W123 servo bypass described/pics

The pics show there is no need for a T from the coolant supply to heater core to bypass. I guess that there is a bypass built in already. But it doesn't specify what hose is the in for heater core and what hose is the out.

Everyone seems to know this but me it seems I think i'm right though, hook em up diagonally?
Doh! Diagram is in the thread above. i never saw it. So to be clear, I had it wrong. Coolant flow to heater core through the double pipe. Just check out the diagram. Its clear. I'm an idiot
Attached Thumbnails
Coolant flow on 1978 300D  for heater and servo?-123_heating_water_circuit.jpg  

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