1986 300SDL I need to replace my monovalve (heater control valve), can I just take out what's in the new valve and pop it in the old valve housing or must I remove the entire valve and replace all the attached hoses? It seems easier to just do a transplant of active interior parts?

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jcciem
'94 SL5000 60,000
'91 350SDL 545,000
'91 350SD 197,000
'00 E55 AMG 77,000

If you buy a monovalve repair kit, you'll get just a cartridge with new seals. That's typically all you need.

Sixto
91 300SE
81 300SD

I just finished a write-up of this repair for the upcoming FAQ page. I've got the procedure and pictures if you want it. Just get me your E-mail address and I'll send it to you. I did it for my 87 SDL it's a peice of cake.

Brothers of The Benz,
My mechanic at my M/B dealer told me that unless you live in very frigid climate; remove that little rascal and never give him a second thought.
SOOOOO living on the Gulf Coast, when the time comes, BYE BYE BALVE.
Happy Trails Beep Beep from The Spiderman in Houston!!!

What exactly would you remove the entire monovalve? What would you do then leave the heater core out of the coolant loop? How would you connect coolant to the heater core if you wanted some heat? After recently repairing my monovalve with a new piston assembly I don't believe you could leave that part out of the monovalvebody. It appears that the climate control unit modulates the monovalve piston to control coolant to the heater core stopping flow at times and allowing flow at times. When mine failed I had constant heat at low RPM how could you live with that in a warm climate?

jcciem,
I recently replaced the heater valve, didnot bother with a rebuild kit as that will probably fail sooner than a new valve. (You know how rebuilt things are.) This job is very simple; three hose clamps and one bolt. The difficulty for me was getting the cables back on. I found that by sticking my tongue out my right incisors and biting with moderate pressure helped.

the bern

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1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs

This monovalve is electrically operated and the solenoid piston assembly is replaced with a brand new one effecting the repair. The whole valve body where the hoses attach is reused as it doesn't wear or wearout. I guess your 240's was mechanically operated via a lever on the dash?

Yes, mine is cable operated.


the bern

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1982 240D 313,000 (4 speed)
1984 300CD 172,483
1985 German Shepherd Dog -Lacey- R.I.P.11/04/05

Hood Stars, Wrist Crowns and Obsession Dobs