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1983 300SD
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Discussion Starter #1
I've been working on rebuilding some climate vacuum actuator pods I pulled from the JY. The single diaphragm pods are going great. Easy if you finesse it and take lots of pictures. They release with a nice shwuuuck just like the new ones I purchased. However, the dual diaphragms... not so hot. The bottom diaphragm comes off fine. But the top diaphragm seems like it's held in place by two pieces of plastic which don't twist or pry apart.

Replacing only the bottom has lackluster results. No swhuck. Does anyone have experience with the rebuilding dual diaphragms or thoughts generally?

This is what happened trying to take off the top on a test pod.

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The good news is for the time being it's not an issue. In combination with JY part numbers and pics I created a reference spreadsheet (apologies on messiness) using the incredible information posted by @nehuge in post 40 of the link below. The only dual diaphragm not in production is 0008005875 (0008003675 on Gen 1). This is identical to 0008004375 other than the linkage arm. The linkage arms on the new units are a better design which both swivel and pop off. By drilling out the rivet on linkage arm on 5875/3675 you could simply pop it onto a 4375. I have a 4375 on the way and I'll update with results.

The reason I thought it prudent to get a thread going is because I assume these will be out of production at some point, probably soon. So we should be hoarding these things before other people get to them. And also, you know, building the body of knowledge for future 126 enthusiasts and keeping them on the road or whatever. But most importantly hoarding.

 

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1989 300SE 232k miles
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I'm chiming in because I need to rebuild a couple of these soon, as they're not working in my '89 300SE. I'd like to follow this thread.
 

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1983 300SD
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843 Posts
Discussion Starter #3
So my new 4375 Vacuum actuator pod came in. I should be prepping my Jeep for Moab but with the recent chop shop scare and the Veggiewagen being back in my garage I couldn't resist. Doing this writeup as the JB Epoxy dries. I'll have to get back to y'all in 3 months or so once i get it in the car.

Donor 5875 on the left and two 4375s on the right. The middle 4375 is about to become a 5875.

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First I drilled out the rivet on the 5875 to get the linkage arm. That and the lowest plastic piece of the body are the only parts we care about. I started with an itty bitty drill bit and move up gradually to the smallest gauge necessary. This is because I wanted to secure the 5875 linkage arm with a piece of a 4375 linkage arm. Not sure if you can see it but I put a small hole in my table. Ikea's finest.

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Rather than being riveted in the linkage arm on the new 4375 is held in with a swiveling plastic piece that just pops open. SUCH a better design. The direction in which it pops open is ambiguous so be gentle.

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Now the fun part. The swiveling plastic piece is designed to hold a rod. We have a flat piece of metal. Two implications here. 1) out new linkage arm cannot be held in place in the same manner 2) the plastic piece cannot close entirely because there is now a piece of metal holding it open ever so slightly. My solution? Start dremlining that ish and figure it out later. I ultimately hit it from every possible angle. I made the depth of the donor linkage arm less deep and the width of it thinner. I opened up the gap between the two inner sides of the plastic piece.

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But I really, really don't want this sucker popping off after being the in dash for a year. So I drilled a hole straight through the plastic piece. When I put the 5875 linkage arm into the plastic piece I lined it up with the riveted out hole. After epoxying everything and putting it on the 4375, I put a piece of the old linkage arm through said holes.

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Note how close the drilled out rivet on the old 5875 is to where the linkage arm on the new 5875 I'm almost done with. With the exception of the new one articulates and swivels!
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It turned out there had to be a lot more dremeling. I forgot that the 5875 had a square opening at the bottoms. The new bulk of the plastic clasp tended to get caught on that square opening. So I again dremeled both the opening and the linkage arm.

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The last step is to swap on the old 5875 lower body piece onto our modified 4375. It takes some finesse. Make sure there's a seal between the bottom diaphragm. But once you do that... Voila! A new 5875. The might not be in production in Stuttgart anymore but they certainly are in my apartment!

A 5875 manufactured in 2019. Notice the one manufactured in 1980 in the background less linkage arm and bottom plastic piece.

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Discussion Starter #4
One other thing. It just occurred to me the springs in 5875 and 4375 could be different. Easy enough fix I'll look into after getting the winch on my Jeep.

And gentle reminder to buy these things now even if you're not planning on doing your dash any time soon. Rebuilding the duals seems to be a no go. And I guarantee you even if the "work" your top diaphragms are in bad shape and they're not working like new. At minimum you can fence them on eBay for twice the price when they're out of production.

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