Dreaded climate control

[kavadarci1]

I have 1979 w123cd and I’m sure the climate control is toast and tons of lines are damaged.
While I have no intentions to fix it to factory specs I do want heat in the cabin.
I’ve read a lot and people talk about mono lick valve in the engine bay which I don’t seem to have it, it’s not there and I think it has been removed.
With that being said I “should” have heat in the cabin because the water is flowing in the cabin.

Can someone describe what do I have to do to get heat in the cabin?
Manual intervention (on and off for the season) is ok with me.

Much appreciated
Thank you

[jsb357]

if the monovalve has been bypassed is the electric pump still in place?

if so powering it up will help push the water at idle and low speed

if not the heater will only get hot at speed


Sent from my iPhone using Tapatalk

[kavadarci1]

Ok,
I don’t know where is the electric pump or how it even looks like.
How can I find out and figure out if it’s working?

Thank you

[jsb357]

see attached

101 is the pump up front on the PS of engine bay

119 is the monovalve housing

122 is the monovalve replacement part

[801mbz]

79 had older servo no mono valve. you can bypass it connect hose from water pump to hose going to heater core a water valve from hard ware store in between to turn on and off under hood. cost 10.00

[kavadarci1]

Hi,
I don’t have mono valve and the pump is there but no idea if it works.
Where do I bypass the connection?
If I don’t have a valve now why am I not getting heat?
I guess the valve will help summer time but I “should” have heat now.

Thank you

[801mbz]

the hose from water pump turns into a pipe then a hose that goes into electric pump that pump is not needed once motor rpms rev water will move good enough for heat. the pipe and hose to the heater from the water pump you want is hidden by ac comp hook it to pipe going into car heater then hook hose coming out of car heater to hose going into head put on off water valve there or by the the water pump pipe call me if you get stuck or need apart call me 801 708 6871

[280EZRider]

If the electric water pump is missing, consider that they are bloody expensive to replace, at least from MB. A brand new manual Heater Control Valve by comparison is around $65, which is a fraction of the cost of the electric water pump. And a manual system of course uses the engine water pump, so that problem is solved.

By using wrecking yard remaining parts from a 240D, you can convert the automatic system to manual probably for the price of the electric water pump alone. This is one of the first things I did to my car many years ago. It's a rather drawn-out process, but it's quite doable.

[kavadarci1]

Hi,
I have done some progress thanks to the suggestions here.

So here is what I know.
From the water pump I have two lines, one goes to the side of the block (bigger hose), the other to the three way split on the firewall.
After removing this hose I found there was a screw inside and the opening to the entry was welded.
This does not look like a mistake but like something that was dekibaretly done to prevent coolant inside the cabin.

So I cleaned everything, replaced the hoses and installed valve.
Up to this point I’m good.
I removed the auxilary pump as there is no fluid going to it, probably doesn’t work anyways.

What I’m confused is from the firewall junction there are two other hoses that go into the servo.

So logically I would think I need loop on these two as otherwise there is no coolant circulation.
Am I correct on this assumption?
I will drive the car later today to see if I’m getting any heat at all with this change .

Thank you so much.

[kavadarci1]

Further updates.
After I installed the valve I took the car for a drive and found coolant leaking from the servo.
Next steps, bypassed the servo and closed the loop.

So now I have thinner line from the water pump going to the splitter in the firewall, two lines going inside the cabin, one line going out and to the servo bypass loop ending in the splitter again.

So started the car no leaks all looks good and car works fine.
Drove it for good 15 minutes and same thing, no heat in the cabin.

Now I’m bamboozled.

What am I missing?
Is there a flap or valve in the cabin I need to open?
Is my water pump too weak to circulate the coolant?
Or is the system clogged but when I blew on the hose coming out of the cabin coolant came from the other side telling me it is flowing.

I can tell someone manipulated the system and Im having hard time finding the oem hoses connections with the climate control.

I appreciate any feedback.

[801mbz]

valve is in off position? other pics I'm not sure what was done turn valve inline with hose

[kavadarci1]

Hi,
Yes in that photo is off as I wasn’t finished.
Everything I described was with the valve in on.

I drew this quick diagram to better explain my setup which might or might not be correct. This car has been full of surprises and custom on off modifications (hacks), so not sure if this setup is accurate to the factory but this is how it is.

The only line that carries coolant to the cabin is the little red line that splits out of the water pump, the bigger goes to the side of the block.
That’s it, the rest I made it in a loop bypassing the servo and auxiliary pump the way I believe others have done.


Appreciate the feedback as the cabin still has no heating.

[jsb357]

The diagram I used looks similar.

My manual heater control valve is now where the pump used to be.

if your valve is on the small vent line that's not enough flow to work.

looking at your diagram again that big red line has to connect
with one on the big yellow lines at some point to work

[kavadarci1]

So, I am looking at that diagram and mine is not like that.
That is a different engine setup from mine.
Is my system hacked at the pump exit and if yes why would they go through blocking the small line on top of re routing the main heater hose?

While I think I get what needs to be done my setup is different from anything I’ve seen so far.

I am having hard time finding this type of diagram for 79 with climate control.

If I were to do what you describe I have to hack main hose coming from the pump.
Also the fluid flow doesn’t make sense to me, I thought water pump pushes the fluid and not retract as the diagram you attached.

[jsb357]

Originally Posted by kavadarci1

I thought water pump pushes the fluid and not retract as the diagram you attached.

I have a 1979 300d and the diagram I provided, minus the pump,
matches my car.

As I see it...

The water pump main objective is to push water through the engine

The water leaves the rear port on the engine, gets accelerated by
the elec pump in stock installations and if the heater control valve is
open then delivered to the heater core and then returned to the engine.

The small vent line in to insure neither the electrical pump or the main
water pump never enters a "dead head" situation.

Like I said, that is how I see the diagram