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Old 01-11-2011, 02:22 AM
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Join Date: Sep 2010
Location: Oakland, CA
Posts: 25
While you are in there, unplug the aux pump

As has been stated, the aux pump (which is generally useless) is not separately fused, unless you consider your pushbutton unit's circuit board to be a large fuse. And that's what it will become when the pump goes. Best thing you can do for it is to unplug the pump.
David Bruckmann, Oakland, CA

66 CitroŽn DS21
72 MB 280SEL 4.5
73 MB 450SLC
76 CitroŽn 2CV6
76 MB 300D
79 MB 300SD
70 CitroŽn DS21 (170kkm)/71 CitroŽn DS21 (137kkm)/72 CitroŽn DS21 (502kkm)/78 MB 300D (1,200,000 km-ish)/79 MB 300D (425kkm)/79 MB 300TD (260kkm)/81 CitroŽn 2CV6 (120kkm)/88 Merkur XR4Ti (209kkm)/81 Peugeot 505 GRD (350kkm)/84 MB 300TD (385kkm)/85 Toyota Camry (330kkm)/86 Renault 9 1.7L (155kkm)/02 Golf TDI (74kkm)
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Old 01-11-2011, 02:40 AM
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Join Date: Aug 2005
Location: Toronto
Posts: 394
Originally Posted by AlanTbird View Post
jeepers, if mine was that easy to access i would pull it out and put in a brass ball valve
summer off and winter on! win win
and then you'd have no control over the temperature in the cabin but you'd have a nice el cheapo repair.

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Old 01-11-2011, 02:37 PM
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Join Date: Jul 2008
Location: Kona, Hi
Posts: 1,385
Having intermitent heat issues with our W123. I have had the MV apart and it looks ok if memory serves. I will check it again. This is an expensive little bugger.
83 300TD (need rear wiper assembly dead or alive)
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.
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Old 01-11-2011, 10:37 PM
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Join Date: Aug 2008
Posts: 97
I just replaced my monovalve. The results have been amazing. Took less than five minutes.

84 300D, 303K
71 MGBGT, ?K
96 GMC C1500, 115K
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Old 02-12-2018, 01:21 PM
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Join Date: Jan 2015
Posts: 261
Old thread, I'm dealing with this now.

I replaced my monovalve about a year ago with an MTC unit. The original was toasted.

Now I've got heat only, with cooler air at speeds. I did notice coolant leaking from the bottom of where the valve would sit. Now I'm thinking I may need an entire new assembly.

Will also look more into the aux pump as well.
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Old 02-12-2018, 05:54 PM
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Join Date: May 2016
Location: Texas Hill Country
Posts: 3,598
The MTC unit is a known bad part. Unfortunately the OEM cartridge shot up in cost about a month ago, so have deep pockets. Don't waste your money on the MTC unit, it will only bring you tears (and a cold car)
'11 Honda Accord EX - "The Daily" 60K
'83 500SL Euro - "The Money Pit" 116K
'86 300SDL - "The Diseasel" 184K
The Diseasel Thread - Everything You Didn't Know You Wanted To Know
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Old 02-12-2018, 06:41 PM
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Join Date: Sep 2006
Location: Middle TN
Posts: 3,445
Scavenge as many as you find in the yards. They are almost free there because the yard people don't know what they are. I'll get the whole thing next time because my spare body is MIA.

You may have to pull up on the center to see the tear in the diaphragm if you don't know what you're looking for.
85SD 240K & stopped counting. 84SD 180,000. Thinking of painting both.
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Old 02-12-2018, 08:08 PM
Join Date: Jan 2010
Location: Back in SC upstate
Posts: 1,236
I have a spare and I'm keeping it close.
84 300SD
85 380SE
83 528e
95 318ic
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Old 02-12-2018, 10:57 PM
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Join Date: Mar 2007
Posts: 156
This morning I replaced a 1year old MTC with a new Mercedes part. Problem solved.
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Old 02-13-2018, 01:13 PM
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Join Date: Nov 2014
Location: Olympia, WA
Posts: 45
I have also been through the mono valve drill. Two things:

1. Replace with Mercedes. The Mtc does not work, and the common symptom is no heat at engine speed much over idle.

2. Be very gentle unplugging the wire to the solenoid. The pins broke on mine, and I had a hard time finding a plug or solenoid without broken pins. In fact, my woes started with broken connector pins. While dealing with that, I decided to throw in the new mono valve I had (MTC). I finally got a working solenoid from a parts yard with the wires cut so the plug does not have to be unplugged.

1985 300TD. 378,000 daily driver
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Old 02-13-2018, 01:51 PM
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Join Date: Jan 2015
Location: Denver, CO
Posts: 134
The inserts are now available from Mercedes. The aftermarket brands usually don't work very well - at least in my experience.

85 300TD 280k
85 300TD 175k
85 300CD 258k
83 300D 316k
83 300TD 275k
81 300TD 171k
95 E320 cabriolet
98 E320 Wagon 4-matic 200k
03 E320 Wagon 4-matic 100k

84 300D
84 300CD
two 63 220SE coupes
two 63 220Sb 4-door sedans
59 219 ponton 4-door sedan
59 190 ponton 4-door sedan
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Old 02-13-2018, 11:18 PM
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Join Date: Jan 2015
Posts: 261
I said **** it, bought this: Klima Design Works | Monovalve and Coolant Circulator Pump Eliminator / Upgrade Kit

We'll see how it does.
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Old 02-14-2018, 09:32 AM
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Join Date: Oct 2007
Posts: 5,599
Originally Posted by MongooseGA View Post
That is pretty cool. I wonder how that would work for the Klima II ?(EVIL Servo)
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Old 02-14-2018, 06:58 PM
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Join Date: Jan 2015
Posts: 261
Hopefully it works well. I've seen people saying they can source everything in the kit for cheaper but for the time I'd spend, $100 seems like a pretty nice deal for everything it claims to do and the parts I won't have to replace now.
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