Duovalve broken stem/valve fix DIY page one. - Benzworld.org - Mercedes-Benz Discussion Forum

gt4rcdude · 11-14-2007, 01:22 PM

Find the thread that shows removal/cleaning of the duovalve. If you find a broken valve/stem, here's your fix.

DIY scale, 1-10? 5

Tools needed:

Drill
1/8th inch bit
Pop rivet gun
1/8th inch rivets with small seats. 3/16-1/2 inch grip range. Aluminum!
Dremel (or similar) with bits and cut-off wheels
Vice
Patience!

I took my valve apart to find this. . .

Problem is the valve stem is plastic and MB wants big bucks to replace the whole duovalve assembly for a 1 cent part!!!!!!!!!!

Carefully put the broken part in the vice with something to prevent marring the valve. It's soft brass. The only part you don't want to damage is the valve seat, this is the shiny ring around the base of the valve.

Grab the dremel and cut-off wheel and cut off the remaining stem. . .

This is what you want. . .

Next, put the pointed wood carving bit in the dremel and remove the plastic carefully from the vavle. . .

This is what you want as a result. . .

Next, grab your drill and a 1/8 inch bit and drill a hole down the center of the valve. Be as careful as you can to drill straight!! After you break through, rotate the drill around to "hog out" the hole a little. Think of it as making a hole the shape of an hourglass. This allows the valve to move on the rivet for better sealing.

This is what you should get. . .

Place the rivet into the valve, make sure it has a little freeplay by rotating the top of the rivet around in a circle. If it doesn't, "hog it out" a little more.

Insert the rivet gun onto the rivet. Pull it just enough to hold the valve without "popping" it. When you pull the rivet, you're pulling the larger head through the hollow stem of the rivet. This expands the stem and holds it in place. What you want to do is pull it through just enough to expand the stem just below the valve. The valve should have a little freeplay so it can move on the rivet.

Note how the end of the rivet is not expanded all the way to the valve! It's starting to look like something! Do not pop the rivet, it's your new valve stem!

Go to page 2 as I could only post 10 images.

gt4rcdude · 11-14-2007, 01:43 PM

Now for the tricky part. The plunger that operates the valve is a specific length. It is designed to work with the plastic POS that has nothing on the back of the valve. With the pop rivet we now have a "seat" that's going to sit on the plunger.

The plunger must be ground down so the valve will open when the plunger is in the "up" position. Here's the difference.

The rivet seat is around .035" so grind down the plunger that amount. It just so happens that the notch cut in the plunger is close to that number, so just grind it down until the notch is gone. . .

Dremel in a couple of notches. . .

Rinse off all the shavings and junk, slide your newly updated valves into the plungers . . .

Carefully reassemble. Here's the final product!!!! Congradulations, you just save a couple hundred bucks!!!

ohlord · 11-15-2007, 09:34 AM

work!true grit and diy innovation.

l-pagan · 11-15-2007, 05:17 PM

whats a duovalve

ohlord · 11-15-2007, 06:08 PM

two valve system that allows the flow of engine coolant into the climate control system that on these model mercedes is a shared system both hot and cool are always avail on demand as the system calls for them with the climate control.
Bad valve or stuck valve and your a/c could be on and have it blowing hot air on one side and cold air on the other or depending where the valve is stuck someplace between the two extremes.Sometimes a whack with a screw driver handle will free them up,just don't whack to hard.

l-pagan · 11-15-2007, 06:46 PM

Thanks

**JOE55** · 11-15-2007, 07:43 PM

Thanks for the great DIY....

-JOE55

gt4rcdude · 11-15-2007, 08:27 PM

I wish I could say I did it for better reasons. My motivation was the thought of being screwed by the dealer for a couple hundred bucks. All for a part that probably costs less than a dime to make. Spend the money and you get the same piece of junk. They should be ashamed of themselves. Almost like they've been following the Chrysler business model. MB has a lot of "brand" issues they need to repair.

I've only owned the car about a month. It's a 98 E300 TD. I'm still wondering if I should just keep my 92 300D 2.5 and get rid of this thing. It's built like an MB should be. The build quality of the 98 car concerns me. Already busted a window regulator. I do love the power and the quiet of the 98 though. It's roomier, looks more modern and at times is a little easier to work on.

I just hate when I have to replace a broken junk part with an expensive new junk part. So you can count on me for future work-a-rounds!

Okay, I'm off my box now.

fju2112 · 12-04-2007, 07:38 AM

for us novices, where do you find this part to get at it, remove it, and try this out...? also if htere were specific part and part numbers you used when putting this new valve together, i'm sure we'd be interested when/if we have to attempt this.

thanks for posting it!

F

ohlord · 12-04-2007, 09:38 AM

the parts or had a buddy make them in a machine shop.
Do you have problems with your a/c system?
if not the typical cool on one side and hot on the other,there is no need to go into the duo valve(located in the area where the ecu and tcu are right in front of them on the pass side back by the firewall,look like two little brushed alum beer cans sitting side by side)