Monovalve Cartridge Repair - PeachParts Mercedes-Benz Forum

Tom Evans · #1 12-05-2019, 02:31 PM

I know there has been a lot of discussion about the quality of third party aftermarket monovalve cartridges. They don't seem to have as strong a return spring as the genuine MB cartridges and suffer poor performance at high RPMs. Mercedes no longer sells the cartridge, but does sell the complete monovalve.

My cartridge that failed was a genuine MB cartridge. I got the Uro repair kit from Rock Auto. When I first put all the new parts in, the monovalve would not snap in the retracted position. I took the rubber part out and soaked it in almost boiling water for a while to make it more pliable. I reassembled it and it has good snap in both directions.

The part number for the Uro kit is 0008350644R.

URO Parts Support · #2 12-05-2019, 06:26 PM

Thanks for the update Tom!

Coincidentally, we just made a running change to the rubber diaphragm in kit 000 835 0644R. We're softening the rubber material, which should remedy the stiffness you encountered, and improve longevity. This improved version should be available in about six months or so.

URO Parts Support · #3 05-17-2021, 12:58 PM

Quick FYI since this has been out of stock for awhile: we should have a production run of the new improved-version URO Parts Monovalve Repair Kit 000 835 0644R / 0008350644R available early June. Link to item on Pelican: TBD

runnersigh · #4 05-23-2021, 08:36 PM

After endless problems with my monovalve I finally got rid of it with Klima's kit and now everything works great:
https://klimakit.com/product/monovalve-and-coolant-circulator-pump-eliminator-upgrade-kit/

BillGrissom · #5 05-31-2021, 07:25 PM

Quote:

Originally Posted by runnersigh

... I finally got rid of it with Klima's kit ...

I did too, except I rolled-my-own for my 1984 300D and my 3 1960's Mopar cars. For the later I block the hot-water flow when the AC system is on. Those have after-market under-dash (knee-knocker) AC units, but same idea and makes it like factory AC cars which had a vacuum-operated water valve. In 2 cars, I used a metal valve which looks identical to Klima's, I recall for $10 on ebay. On the other 2 have an all-plastic water valve for Fords, also $10 on ebay. On one car, I use a cute little vacuum switch for a Porsche ($6 ebay) and the others a vacuum switch from a 1980's Dodge (grabbed assembly at junkyard years ago). I had to de-solder the 300D connector (saved) and solder on a mating connector. In the 300D, it is interesting to see the water valve open and shut at about a 3 sec period. Presumably the mono-valve does the same if you could see it move (on-off control, can't see).

On my 1985 300D, I installed a monovalve for a 1986+ 300D since a used one was cheap on ebay (then not now). I put it where the aux water pump sits and extended the wires to a new connector for it (larger pins). I took out the aux pump years ago, since unneeded and a potential source of dash fire (unfused) or coolant loss. Some guy here fussed I was wrong and that pump is essential, yet the Klima kit tosses it and 99.9% of U.S. cars have acceptable heat without one. Germans are overly-fussy about cold and drafts.

vwnate1 · #6 06-01-2021, 12:09 PM

Thanx for this thread .

My brother's recently acquired 1987 W126 300SDL has no heat and I wonder of the Monovalve might be mis assembled ~ does anyone have an image of the parts in the correct order they can Post ? .

Interestingly, the AC's charge was a little bit low, we added some and it now blows cold again .

I've subscribed to get the image when posted or the link to the revised Uro part when it arrives this month .

TIA,

ykobayashi · #7 11-06-2021, 11:54 AM

Has anyone tried the updated URO monovalve? I tried an MTC and it was a complete waste of money.

This one looks different. Is this the revised unit our URO engineer is talking about?

https://www.pelicanparts.com/More_Info/64118390132.htm?pn=64-11-8-390-132-M253&SVSVSI=3336&fs=0

It’s kind of funny, the URO pn is Uro Parts 000-835-06-44R.

When I search my 82 300SD on pelican I get the Uro Parts 000-835-06-44 which says temporarily unavailable but perhaps this is the older unrevised unit without the softer rubber? It comes up as a BMW part.

I got kind of curious because there are a bunch of people refurbishing monovalves on eBay and selling them for $250. I’d like to rebuild my own if I can get a quality diaphragm.

I suspect this is the diaphragm they’re using but it isn’t easily found on Pelican while searching for my 82 300sd or my 85 300D.

I bet the R means revised.

If this is the right one Pelican has to get their catalog system pointing to it or they aren’t going to sell any. I think this is what I need but all I’m pointed to is the useless MTC part.

This is what comes up when I search under my 82 300sd. It’s a pretty sad state of affairs if URO went through the trouble of making a better updated part and stocking it at Pelican and we cannot even find it for our cars even though it’s right there on the shelf.

https://www.pelicanparts.com/More_Info/UR0008350644.htm?pn=UR-000-835-0644&SVSVSI=3336&fs=0

“Somebody needs to fix this!” - Jonathan Van Ness

https://youtu.be/SX1HQlIecZk

vwnate1 · #8 11-06-2021, 11:51 PM

Yes, they sent me one and the car has been sitting across town undrivable...

Dammit .

URO Parts Support · #9 11-08-2021, 05:49 PM

Hi guys, we took new photos of our updated Heater Monovalve Repair Kit 000 835 0644R.

We have several hundred in stock and ready for shipment. (Our latest production run has code "8863" in the bottom right corner of the label, future runs will have a higher number.)

ykobayashi · #10 11-09-2021, 07:05 AM

Thanks! I’ll order one.

BillGrissom · #11 11-09-2021, 11:18 AM

Good to see that URO reads the feedback and responds. I have had good luck with many URO parts, which cost sometimes 5x less than the exorbitant "correct" M-B brand. I wish all companies would be as pro-active.

vwnate1 · #12 11-09-2021, 02:52 PM

I have had good results with Uro parts .

I need to get caught up and drag my 300CD home and try this part .

ykobayashi · #13 11-10-2021, 08:16 AM

Yes, my experiences with URO have really improved over the last four years. Prior to that a lot of the stuff was really inexpensive but the reject rate was high. I’ve been very appreciative of the quality and fittment improvements recently. All this in an environment when many of the OE parts are going NLA in very short order.

Amazing they read this too.