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  #46  
Old 07-01-2013, 06:50 PM
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Quote:
Originally Posted by freesoul View Post
maybe its just the valve and not the whole assembly? The guy has been around forever, German guy with thick accent thats why I stopped in last Saturday with a photo. His son usually handles the parts but he is on vacation
Could be an old (NOS) part with an old price. Lucky you!

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #47  
Old 07-02-2013, 09:47 PM
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Here is what I got for $95
Attached Thumbnails
W124 Climate Control Vacuum Valve Repair DIY-20130702_205528.jpg  
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  #48  
Old 07-02-2013, 10:02 PM
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Quote:
Originally Posted by freesoul View Post
Here is what I got for $95
Looks like the early style without integrated recirc pump. Is that what's on your car now?

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  #49  
Old 07-03-2013, 11:25 AM
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Quote:
Originally Posted by gsxr View Post
Looks like the early style without integrated recirc pump. Is that what's on your car now?

no. Just called them and am waiting to hear back....
I didn't look closely enough to see if the pump was part of the same piece on my car but it is.... hope this doesnt mean a $500 part.... I'll just clamp off the coolant hose if that is the case
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  #50  
Old 07-03-2013, 11:26 AM
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Quote:
Originally Posted by Jeremy5848 View Post
The solenoid pulls the brass pointy valve up, yes, allowing coolant to flow through the heater core.
but the brass point is not connected, it just fits in the sleeve so how does the solenoid retracting pull it up?
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  #51  
Old 07-03-2013, 11:43 AM
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Quote:
Originally Posted by freesoul View Post
but the brass point is not connected, it just fits in the sleeve so how does the solenoid retracting pull it up?
The water flow pulls the pointy brass thing up (flow is towards the front of the car at that point) allowing coolant to flow past the valve. When the engine is turned off, the brass pointy thing slides down under gravity (Warning! Does not work if car is parked upside down!) thus blocking the backward flow of hot coolant into the heater core (acts as a "check valve"). In theory this keeps the heater core from getting full of hot coolant and messing with the a/c for the first couple of minutes back in the car on a hot day when you really want the a/c to work RIGHT NOW!!!

Hope you don't have problems returning that wrong monovalve.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #52  
Old 07-03-2013, 12:22 PM
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Quote:
Originally Posted by Jeremy5848 View Post
The water flow pulls the pointy brass thing up (flow is towards the front of the car at that point) allowing coolant to flow past the valve. When the engine is turned off, the brass pointy thing slides down under gravity (Warning! Does not work if car is parked upside down!) thus blocking the backward flow of hot coolant into the heater core (acts as a "check valve"). In theory this keeps the heater core from getting full of hot coolant and messing with the a/c for the first couple of minutes back in the car on a hot day when you really want the a/c to work RIGHT NOW!!!

Hope you don't have problems returning that wrong monovalve.

Jeremy
aha thanks that is what I suspected. But how am I getting heat in the cabin if the default is stuck down and cutting off the flow? When I pulled the solenoid off the diaphragm is not broken and it is in the down position.

I don't anticipate any problems returning the part.
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  #53  
Old 07-03-2013, 04:48 PM
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Monovalve

Quote:
Originally Posted by freesoul View Post
aha thanks that is what I suspected. But how am I getting heat in the cabin if the default is stuck down and cutting off the flow? When I pulled the solenoid off the diaphragm is not broken and it is in the down position.

I don't anticipate any problems returning the part.
"Stuck down and cutting off the flow" is only when the engine is OFF; the brass pointy thing acts as a check valve, preventing hot coolant from going backwards. When the engine is running, climate control on and NOT calling for heat, the monovalve gets power and the valve goes into the position where the by pass line is open and the line through the heater core is closed.

If power to the monovalve fails, the default position allows hot coolant to flow through the heater core, so that you always have heat to melt an iced-up windshield in the winter. That is a safety decision on the part of Mercedes. Obviously, such a failure in the summer is not very much fun.

It is also possible that someone before you put the hoses on the monovalve incorrectly. The two spigots at the bottom go to the firewall where they connect to the heater core; the top spigot (in the section that tends to crack) goes to the bypass line from the head and the little spigot on top is capped off. The heater core has one hose in and two out because it is the same heater core used in models with manual climate control, which have dual-zone heat controls (these were not officially imported into the USA but we got the same heater core).

Here is a crude drawing of the plumbing:



Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Last edited by Jeremy5848; 07-03-2013 at 04:52 PM. Reason: Add drawing
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  #54  
Old 07-03-2013, 06:48 PM
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The plumbing to the washer bottle is odd - the pump has to fight flow from the head. Why not heat the washer bottle from the head and return downstream of the pump?

Sixto
87 300D
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  #55  
Old 07-03-2013, 07:07 PM
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Here's how the 1995 E300D Monovalve Works

I took my spare monovalve apart and played with it, figured out how it works. Here's how, with pictures.

In "normal mode" the Automatic Climate Control (ACC) calls for heat. Power to the Monovalve is OFF. Hot coolant flows from the back of the head through the heater core (in 1 pipe, out 2 pipes) and through two rubber hoses to the lower twin inputs of the Monovalve. The "float valve" (brass pointy thing) is pushed up by the flow of coolant and the coolant flows through the valve, helped along by the auxiliary pump, and returns to the thermostat housing.

If either the ACC or the monovalve coil fails (electrical failure) the float valve will still be pushed up and hot coolant will still flow through the heater core. This guarantees heat to clear a frozen windshield in winter. It also guarantees an uncomfortable car if this failure occurs in the summer, oh well!

When the engine is off, car parked, the float valve sinks to the bottom, closes the valve, and prevents hot coolant from flowing backwards from the radiator into the heater core. In theory this should prevent the climate control system from blowing a lot of hot air when you re-start the engine and re-engage the air conditioning.



In "bypass mode" the Automatic Climate Control (ACC) DOES NOT call for heat. Power to the Monovalve is ON. Hot coolant cannot flow through the heater core because the float valve is forcibly closed by the electric solenoid. However, this same solenoid action opens the bypass valve, allowing hot coolant to flow from the head, bypassing the heater. The coolant flows through the bypass valve, helped along by the auxiliary pump, and returns to the thermostat housing.



Please note that this is a very simplistic explanation focusing on the way the Monovalve works. ACC actually pulses the Monovalve on and off to control HOW MUCH hot coolant is allowed through the heater core, thus regulating the temperature of the passenger compartment. This can occur even if the air conditioning is working; it's especially nice in humid climates to have the a/c freeze some of the humidity out of the air even if the heater is on a little bit.

Except for a very few late-late-1993 (~May 1993? production) 300D-2.5 cars (W124.128, OM602 Turbo), this special monovalve (001 830 40 84) is unique to the OM606NA engine in the 1995 E300 Diesel (W124.131). My guess is that Mercedes did this so that there would always be a constant flow of coolant from the back of the head, thus keeping the head at a more constant temperature, thus improving smog control. I invite you to come up with a better guess.

It is possible that one could simply block off and abandon the bypass line and use a "regular" (separate) monovalve and auxiliary pump, or even the simpler and less expensive combined monovalve/pump (001 830 39 84) used in the 1994-95 E320 gasser. If you choose to go that route, please let us know whether your engine burns up or not.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #56  
Old 07-03-2013, 07:08 PM
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Quote:
Originally Posted by sixto View Post
The plumbing to the washer bottle is odd - the pump has to fight flow from the head. Why not heat the washer bottle from the head and return downstream of the pump?

Sixto
87 300D
I may have that arrow backwards.
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #57  
Old 07-07-2013, 04:51 PM
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I put 12v to mine and although i got a little sparking- no thunk or other noise to indicate the valve moving. Maybe I'll try to find one at a used parts yard, there is one for foreign cars not far away.

When I put vice grips on the line going into the heater core (from the wiper fluid tank) I get no heat in the cab.
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  #58  
Old 07-07-2013, 06:01 PM
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Diagnosis

Quote:
Originally Posted by freesoul View Post
I put 12v to mine and although i got a little sparking- no thunk or other noise to indicate the valve moving. Maybe I'll try to find one at a used parts yard, there is one for foreign cars not far away.

When I put vice grips on the line going into the heater core (from the wiper fluid tank) I get no heat in the cab.
If the monovalve leaks internally, the metal parts of the solenoid can corrode and refuse to move. It may be possible for you to remove the 4 screws and take the solenoid coil off of the valve body. If there is corrosion but not too much, it might be possible to clean it up with fine steel wool and save the purchase price of a new monovalve.

OTOH, an internal leak may continue to leak, making the repair only temporary. Regretfully, the seals cannot be purchased separately.

Incidentally, the metal solenoid coil is common to some (but not all) monovalves. If you have a chance to pick up several in a junkyard they might come in handy (I paid $7 for the last one I bought a few months ago -- tell 'em it's a "heater valve."). A monovalve that has not leaked will last a long time even in a junkyard.

The vice-grip trick confirms that the heat you are getting in the cabin is from coolant passing through the heater core when it should be off. That pretty much pins down the cause to the monovalve.

Jeremy
__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970
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  #59  
Old 07-10-2013, 10:48 AM
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I got the correct part today at a junkyard, $60 and they tested it before I bought it. Came from a gasser 124.
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  #60  
Old 07-10-2013, 10:56 AM
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Brian Carlton's [in]famous response haunts me How can the correct replacement for a Diesel only part come off a gasser? What am I missing?

Sixto
87 300D

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