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#17
06-12-2019, 05:24 PM
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On w123s I’ve found that a 1” size PEX ball valve fits perfectly in the heater hose right in front of the aux water pump. I have also eliminated the mono valve all together with a PEX elbow.
It is designed like several other things in Mercedes. For its failure to result in a safe condition. If your mono valve takes a crap at least you will be able to de frost/fog the windows.
__________________
Current fleet 2006 E320 CDI 1992 300D - 5speed manual swapped former members 1984 300D "Blues Mobile" 1978 300CD "El Toro" 
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#18
06-12-2019, 05:46 PM
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On the ball valve subject.
I use a 3/8" pipe thread valve and a 6" long piece of 3/8" pipe cut in half for a hose connection ( be sure to deburr the cut end ) . A barbed fitting would be better but this has worked on 4 cars without issue, just be sure to check hose clamp tightness after a few heat cycles. A 3/8" pipe has an od between 5/8" and 3/4" making it a stretch or clamp down to common hose sizes. Haven't had an issue with coolant flow being restricted. I'd recommend a larger valve for a 1980 SAAB 900 because the hoses are 1" and it gets cold in Sweden. The valve needs to be between the OUTLET of the engine coolant flow and INLET of the heater core. On my 97 SL and C , the stock valve is on the heater OUTLET. Adding a valve to a non valved / no AC car makes a huge difference no matter what brand. Many heater boxes have leaky air flaps and even it they did seal, you have this hot heater core under the dash radiating heat. Factory cable valves were common on early 70's Fords and AMC products and would work if you could find one. Look through a Everco / 4-Seasons / Murray buyers guide for other possibilities. A 2 connection valve from a 99 Ford Ranger would work with the mods I've outlined below because the valve defaults to open when there isn't any vacuum. Some cars need coolant to flow between the engine outlet and inlet for proper thermostat operation. I have a Chrysler PT Cruiser ( needed a box on wheels ) and used a 4 connection valve from a 99 Ford Ranger to maintain flow past the thermostat but block off the heater core. You will need to cut off the vacuum chamber and hook a zip tie to the lever to keep the valve from moving. Why does MB use a pressure to close valve that defaults to open? I'm wondering if some systems modulate the valve, I've never hung a meter on my cars to find out. I do know that most other brand of cars default to heat / defrost when there is a failure so this no power open would be a fail safe mode.
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#21
06-12-2019, 08:06 PM
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Quote:
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#24
06-13-2019, 08:33 AM
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I saved this link to a recommended ball valve from a past thread. probably accurate.
https://www.amazon.com/gp/offer-listing/B00MA9DQ50/ref=dp_olp_new_mbc?ie=UTF8&condition=new
__________________
1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI
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#25
06-14-2019, 12:00 AM
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Those who live in cold weather climates prefer the monovalve.....
I think I'll try the Amazon valve on my brother's battered old 1981 W126 . ? I thought the heater hoses on the 5 cylinder OM617 turbo engines were 15MM (5/8") ? . TIA,
__________________
-Nate 1982 240D 408,XXX miles Ignorance is the mother of suspicion and fear is the father I did then what I knew how to do ~ now that I know better I do better
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#26
06-14-2019, 07:27 AM
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Quote:
Maybe use two on each side (assuming there's enough room)?
__________________
1991 300D 2.5 "Rocinante" 2002 Golf TDI "Teen Spirit" -------------------- 1984 300D 1966 Mustang I6 3sp 1985 Mazda RX-7 GSLSE 1982 Toyota Supra 1977 Datsun 280z 1971 Datsun 240z
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