Another monovalve question, please help - PeachParts Mercedes-Benz Forum

Paul W · #1 01-25-2008, 10:52 PM

I was trying to figure out why my car does not heat up at lo RPMs. When I turn on my heater my temp guage drops fast. I check the aux water pump and it works. I checked the monovalve and it was not "clicking" as stated in other posts. I pulled the top off and used some steal wool to clean up the shaft. It now clicks. My question: does the shaft normaly have antifreeze around it, or does that mean the diaphragm is torn. I have searched the forum and web for a couple of hours, but can not find a picture of the inards for a 87 300d. Plenty of pictures for the older style. Any help would be great.

zsmith29 · #2 01-26-2008, 01:42 AM

I just changed mine recently. Is the diaphragm still good. That tends to be the trouble spot w/ them.

turbobenz · #3 01-26-2008, 01:44 AM

I used aquarium sealant to patch up my valve diaphram, has been working great now for about two weeks

babymog · #4 01-26-2008, 10:30 PM

Seems like coolant around the plunger/shaft would indicate a ruptured diaphragm, I'm interested in the answer though.

Also, et me know if you need an '87 monovalve, I might have one (have to look to be sure).

LUVMBDiesels · #5 01-27-2008, 09:02 AM

I don't think a good monovalve would let coolant go past the diaphragm.

Replacement inserts are pretty cheap and it is a ten minute fix. I would also check to make sure that your coolant is at the right level and that you do not have any air bubbles trapped in the system.

Paul W · #6 01-27-2008, 09:29 PM

I changed out the antifreeze and tried to get all of the air out of the system. I will check again and see if I can track any down.
I have looked all over for the kit for the 87 300d. All I can find is the ones for pre 86. I searched all over google with no luck. Being new to these cars I am not sure what other years will work. The ones pictured for an 85 just does not look like it will fit. Does any one know where I can get the kit?