Monovalve repair

[shadetreemechan]

What are folks doing now that Bosch has discontinued their monovalve repair kit for the ACC?

I called the dealer yesterday and it is NLA from them as well.
All I see online is the MTC aftermarket and the reviews seem pretty universally terrible.

I also saw on ebay where just the diaphragm was for sale. Has anyone tried going this route?
My 85 300TD has a tear in the diaphragm.

[rocky raccoon]

I managed to find an OE insert last year, I think on this site. It is a major difference BUT ..... One can buy about 6 of the MTC brand for the price.

To answer your question, buy a number of MTC inserts and just be prepared to change them every year.

[shadetreemechan]

I was prepared to pay dealer prices yesterday if I could find one. The bosch that just went bad in my 85 was in there for a dozen years working flawlessly. I want that again......

[Sugar Bear]

i've read that BMW inserts could be used. May be worth a look.

Good luck!!!

[TantaElsie]

Great question and I've the same problem as the monovalve insert on my car has a torn diaphragm, heat is a bit anemic and it's starting to get cold. Would certainly be good to follow up on the BMW, perhaps from an e28?

[TantaElsie]

https://www.pelicanparts.com/More_Info/64118390132.htm?pn=64-11-8-390-132-BOE&gclid=EAIaIQobChMIkMOXrNq95QIVRdbACh0VSQReEAQYAiABEgICIPD_BwE


looks pretty similar

[TantaElsie]

BMW part# 64 11 8 390 132,

[rocky raccoon]

Checked ebay using the BMW part number. Looks identical and the listing is for both BMW and Mercedes. Ebay also displays several "heater control valve repair kits" that appear to have replacement diaphragms.

[shadetreemechan]

i just googled that part number and it came up here in Pelican parts as a genuine BMW part at $154.
I wonder why it doesn't cross reference. I may try to make some phone calls. I would (though I would hate to) pay $154 for another 12 years of trouble free performance from my ACC. I am not looking forward to putting a crappy insert in. I did that three times before I learned my lesson and bought a good one last time.

[TantaElsie]

This is a great post. A thoughtful discussion on the monovalve issue and some real answers. Give it a careful read, it's fun.

https://www.benzworld.org/threads/monovalve-mtc-bosch-or-bmw.2507129/

[okyoureabeast]

I recall someone made a drop in modern replacement for $100. Might be the same folks who made a modern upgrade of the evil Chrysler servo. The name escapes me!

[valvecovergasket]

Originally Posted by shadetreemechan

i just googled that part number and it came up here in Pelican parts as a genuine BMW part at $154.
I wonder why it doesn't cross reference. I may try to make some phone calls. I would (though I would hate to) pay $154 for another 12 years of trouble free performance from my ACC. I am not looking forward to putting a crappy insert in. I did that three times before I learned my lesson and bought a good one last time.

if it makes you feel better the monovalve for the w124 om606 cars is ~$900 from the dealer. and uses the same brittle plastic that has doomed many of the previous ones (my car is on its second factory valve, and i had to reseal the plastic portion already)

[BillGrissom]

That BMW parts looks like the simplest approach, though pricey. There are several other options. One is that someone packages a kit from later M-B parts which has a vacuum on-off valve and electric vacuum switch to actuate it. Similarly, many U.S. cars had vacuum-operated heater valves, many spring-loaded so vacuum to open (or vice-versa). I have a $7 plastic one for a Ford (for my classic cars, but could use on my W123). Just get the polarity right: 12 V on (from push-button box) stops the flow.

Another approach is to install a W124 valve. You have ample room if you rip out the silly "aux water pump" to install it at the front there. Extend the control wire and add a section of 5/8" hose where the monovalve sat. One guy here did this. I have a W124 valve in case I run out of W123 parts. My 2 300D's don't have the aux pump and I get plenty of heat.