I have a friend that is currently working on fabricating a quality solution to this issue (Dutch, same fellow making the pivot mount balls, bless him). But, it seems like it will be a while.

The issue with whole new construction is the line end fittings. See attached picture.

However the check valve and a fitting for the 2 little nipples and rubber hose could be provided and the owner could remove the plastic hose/tubing themselves and replace it with the rubber hose.

Another way would be to cut the plastic hose/tubing as close as possible to the stock Check Valve Assembly and use rubber sleeves to attach the new check valve and nipples. That leaves most of the plastic line/hose intact.

I am in Maine, but would be happy to Paypal you and pay for shipping if you're interested in parting with a spare. If not no worries.

I'm not sure what's going on with PMs - possibly it's because my account is too new.

I'm thinking that's what I'll do if buying the part doesn't work out. In my case the hose and metal fittings are intact, only the check valve/nipple is broken.

I've been curious about the material of which these lines are made, since I got my 240D. I don't think it's plastic as that wouldn't hold up to the temperature extremes and harsh under hood environment, in general. Extreme heat or cold and everything in between and they don't lose their grip, shape, texture, etc. I'm guessing/speculating possibly nylon or maybe even teflon? Does anyone know for sure? Whatever it is, it's very strong and quite stable through all operating parameters and age.

Is the problem that the nipple on the check valve is broke? If that is the case, then carefully drill the broken nipple area to accomodate another piece of tubing (copper, plastic or whatever you can find) to act as a new nipple and epoxy that in. Have done that several times and it works. A good source of nipples are windshield washer line connectors.

I did a quick look and didn't find any of my spare check-valve sections on top. It would be too much digging to find them. Sounds like just the plastic nipple on the check valve snapped off. That is common and could easily happen on a used one you source. You could do like me and others. On one, I cut it flush, drilled a tight hole for a small copper tube to serve as a nipple. To be safe, I epoxied it in. Worked for years until I found a pristine one at the salvage yard when picking other stuff.

Just thought I'd update this thread to say that I ended up drilling out the broken check valve hole and gluing in some sturdy vacuum line, per the suggestions up-thread. Went slow, was careful to remove all the plastic that I drilled out. It's doing the trick for now, no delay in the fuel shut-off, etc. I decided that chasing down a more complex replacement or expensive part isn't worth the effort until I go over the rest of the vehicle and make sure it won't need major repairs after sitting for a long time. Thanks everyone for your suggestions.

Thanks for getting back to us on your solution.

JB Weld makes a plastic bonder that is stronger than the original plastic. I used it on a headlight bezel and the bezel broke somewhere else but the repair was solid.

Concerning the JB Weld Epoxy the slow curing one takes a higher temp then the fast curing JB Weld. I also think the slow curing one is stronger but have no proof.
Duro is another company that is still around used to make Epoxy in that has the same temp range as the slow curing JB Weld.
If you think you are going to have a temperature issue be sure to read the label.

With the fast curing JB Weld you could make an on the road repair on your vacuum line if nipple broke off as long as you are careful to reinforce it with enough epoxy.

I have used brand X type cheap epoxy and it sometimes won't even take the heat in the interior of a car on a hot day.

If you look closely at the check valve with the two fittings located on the valve they aren't just plain open tubes. There are numbers stamped into the plastic, 0.5 and 0.6. Those are restriction values. One fitting is even color coded with a white ring to signify they are different. A general drill-out repair will get the system closed again and often works fine but if you ever start to notice things like a change in shifting or engine shut down you could possibly adjust it out farther down in the system or you could add in Mercedes' little color coded plastic inline vacuum restrictors to make adjustments. This is just an observation for people who are still experiencing vacuum issues after a repair.

Hi guys - good news, we'll have Brake Booster Vacuum Hose 123 430 74 29 available in a few months! Shooting a photo of an early production piece this afternoon, and will share it asap.

URO:
Your website shows 20 of these in stock but no way to add to cart. I need one. Timing on production?

It appears there is someone making a replacement per Diesel911's comments. Thoughts on this one?
https://lermscustoms.com/products/w123-brake-booster-line-replacement-or-repair?variant=40430502805654

I'm also finding a supplier for just the check valve with the 2 nipples:
https://ppembzparts.com/i-30510935-mercedes-brake-booster-line-check-valve-double-vacuum.html
Thinking I might use Diesel911's suggestion to repair mine, "Another way would be to cut the plastic hose/tubing as close as possible to the stock Check Valve Assembly and use rubber sleeves to attach the new check valve and nipples. That leaves most of the plastic line/hose intact."

Hi Chris, good news - our warehouse (we only sell wholesale) just received the production run and these should be available from Pelican soon. We'll ask them to add it to their catalog.

Edit: Pelican says the hose should be available on their site by the end of the week.

Good to know! Mine is more epoxy than plastic now. Looks like I sneezed on it.