Mono Vale Rebuild Question
 

I picked up a mono valve rebuild unit for my '85 300D. Can anyone explain how I do this? Do I have to remove the vale unit or can I just open the top and replace the thingamabob.

Thanks

I'm not familiar with the 300D but if it is similar to the 300SE (and probably is) than yes, you just pop the top open and replace the unit. _ on my car there were two such pistons, not one. Also there was a cylinderical"sleeve" that I removed from the defective part and put on the replacement kit , before dropping it back in to place.
good luck.

Yes, it's a five minute job. There are four screws on top, remove them, replace the diaphragm/plunger unit and reinstall. Then make sure you refill any lost coolant.

Good luck,

Thanks guys! i have a 300Se that needs it also. Much appreciation for the good info.

my thanks to you guys as well, the description of the unit along with other entries elsewhere helped me id the right location of the mono valve, popped off the cover, switched out the unit and voila...I have heat again....

good stuff. cheap solution.

Mr. Bill,

If your 90 SE is anything like my 91 SE, you'll have to move the diagnostic port out of the way (2 screws behind the transmission dipstick) and a 1/2" OD coolant hose just above the monovalve. Go easy on the hose because it's connected to a plastic fitting.

You don't have to disconnect the monovalve wires or any wires for that matter.

The sequence of washers on my car from top to bottom is small thick washer, wave washer (part of kit), small thin washer, big washer.

Sixto
91 300SE
81 300SD

Right you are. I did mine last week and experienced exactly what you said. I didn't disconnect the 1/2' hose, just worked around it. Yhe screen had a lot of black gunk on it and the waffle spring washer was broken. Now I'm riding around in warm comfort!

Oops, I didn't see the date of the original post. My screen had rust colored silt. I'm surprised anything flowed past the screen. The old wave washer looked just like the new one.

Next job is to check the cabin temp sensor. The intake doesn't suck on a piece of tissue paper like I read it should. I hear a whir from the dash so hopefully it's just a loose hose.

Sixto
91 300SE
81 300SD

Monovalve meltdown ?
 

Well, after repairing my monovalve with a fast lane kit - 87 300SE euro (which has two plunger/pistons, not one ) I suddenly get constant heat coming out of the defrost vents.This is with the temp dials at minimum, and the blower off. Worst yet - there is a strong odor of hot plastic, as if something is ready to melt down or burn.
I checked under the hood and these new replacement plungers in the monovalve are very hot. Should they be ? anyone have this problem before ?

liquid wrench?
 

I can not get the last screw off on the mon valve cover. Whenever I work on my 1984 300D, whether I am working on replacing the seat spring, whatever, The 18 year old screws never come off no matter how much liquid wrench I use. I've grown accustomed to buying parts and letting my mechanic do the labor. I'm not even goin to make an attempt on replacing the schocks. I can imagine the mud soaked nuts & bolts are a pain to take off.