It is impossible for water/radiator fluid to be sucked into the vacuum system. The vacuum pod is entirely separate from the water valve, and is connected by a mechanical link.

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Richard Wooldridge
'01 ML320
'82 300D 4.3L V6/T700R4 conversion
'82 380SL, '86 560SL engine/trans. installed
'79 450SL, digital servo update
'75 280C

That's what I wanted to hear. Thanks.

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1983 CD
1958 Studebaker Packard (being resuscitated)

My auxillary water pump to the duo valves sticks. Any fix or just buy one?
If I wack it with a wrench it spins for a day or two.

Thanks

Someone posted a DIY thread on this forum giving instructions for disassembling the aux coolant pump, cleaning it all out (accumulated crud, etc.) and reassembling it. The forum's search function should find it for you (try "aux pump DIY" or something like that). If you don't want to bother, you can always buy a new one.

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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

Fried ACC Board (picture) due to frozen aux pump?
Fried ACC Board (picture) due to frozen aux pump?

Aux. Water Pump takes out CCU
Aux. Water Pump takes out CCU

I rebuilt my Auxillary water pump
http://www.peachparts.com/shopforum/general-information/38739-i-rebuilt-my-auxiliary-water-pump.html#post219859

Fixed Auxiliary Water Pump!!
Fixed Auxiliary Water Pump!!

Bringing this thread back from the past........

I think my ACC unit is sending the correct voltage and ground signals to the monovalve. I think the valve plunger is not responding or the electromagnet is not working. Junkyard to find another electromagnet, I go today.

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daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

Can you make a simple test when you get it working?

On both the SD and the SE I find that the vent temps in economy are 10-15 F. above ambient, no matter how long I leave the blower on high. The system clearly knows that the interior is warm and is trying to bring it down with ambient air.

But, my suspicion is that the monovalves leak, even when closed. Not a terrific amount of leak, but any leak is more than sufficient to compromise the a/c in a big way.

Since it has happened on two of my vehicles now, I'm curious if it is a generic problem, likely invisible to most, and the a/c capability of the vehicle suffers dramatically as a result.

If true, this would beg for a small ball valve in the line to the heater core during the warmer months.

Agreed. My monovalve gets plugged every spring. Only slightly less convenient than a ball valve.

Can you explain how you do that?

Bought a tapered rubber plug at Ace. (Shaped like a wine bottle cork.) Remove the supply-side hose at at the monovalve , insert plug, reconnect hose.

That's easy.

Thanks. I'm doing it.

I'll bet it solves a lot of complaints regarding "cooling sucks".

An easier but more brute force method is to pinch the hose with 2 x 1/2" hardwood dowels and 2 wood screws.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

And another that I may try is using a fuel line clamp. If that brings the cabin temps down during the warm months, maybe a more permanent fix.

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1985 300D-189k The 'UD', Ivory and Pinkamino
1979 300D-211k Dark Gray, Parchment
A 1980 Harley-~166k and
A 1994 Ford diesel pickup-349k and
A 1990 gasser Volvo wagon-145k

Okay....Brian and everyone else. Here are my findings:

1. The 1987 Champagne monovalve was replaced about 14-15 months ago......
2. I took it out this afternoon and hook 12 volts up to it.
3. It pushes out less than 1/4 of an inch with voltage applied from the battery --- the hot wire was on the outside most post.
4. If I manually pull it out, it has room to come out ....guessing 7/16ths, 3/8ths at least.
5. So....I'm thinking the plunger is not going OUT far enough.
6. Didn't make it the junkyard to find a different electromagnet --- can't believe that might be the issue.

I took a piece of stiff copper wire and wrapped it around the plunger UNDER the rubber seal, so the plunger would be stay OUT. Reassembled and left the thing unplugged. I've got two of these, so I'll probably make one winter and one summer and leave it.

I haven't done a test drive....but usually I can feel engine warmth in the dash area very quickly and I let the engine idle while I was removing the glove box and transmission tunnel cover on the passenger side. I'm tackling the defrost vent panel vacuum pod next. It won't close all the way sometimes.....

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more

I thought about doing something like that....but the 4 screws on top of the monovalve seemed easier to get to for me. More than one way to skin the cat.

__________________
daw_two
Germantown, TN

Links:
Sold last car --- 05/2012 1984 300D Light Ivory, Red interior
Cluster Needles Paint
New Old Stock (NOS) parts

Past:
3/2008 1986 300SDL "Coda"
04/2010 1965 190D(c) "Ben"
& many more