I was doing cooling system repair/maintenance stuff on my 1976 R107 450SL.



I was set to replace those two lovely bypass hoses and do a tide flush followed by a citric acid flush .



While removing stuff to do that I snapped off one of the two "BLUE" plastic Thermal Vacuum Switch ports off. (BTVS)



I brought the tiny BTVS to my old fashioned and wonderful/super valuable to me "Marshall's Hardware store to see what I could find to fix that snapped off tiny port.



I also went to Marshalls to design a way to Attach a garden hose to the block drain hoses so I could block back blush the cooling system. Before most projects I walk the isles of Marshalls to plan my project.



Two days passes since my hardware store visit. It's about 6pm and I am ready to tap water flush my system with the garden hose.



I see a nice stream of water coming out of the top of the intake manifold from the hole where the BTVS is supposed to be threaded into.



I go to my little box I put all the stuff I brought to Marshalls into and can't find the BTVS in it.



A quick mind back track review of my visit had me recall from my minds eye the BTVS in my right hand as I showed Marshalls associate, Chris the BTVS while I stood next to the copper tubing. I asked him if there was an in-between size of tubing for what they carried in stock. He said there is but they don't have it.



I then looked for other solutions since they had all kinds of material for tubing in that section.



Standing there as the water streamed from the BTVS hole in the manifold, I couldn't remember putting the BTVS back in my box after showing it to Chris at the copper tubing.



Friday morning at 7AM when they opened I went to Marshalls. The tiny BTVS was sitting on the shelf where the copper tubing is.



It appears the BTVS is obsolete no one has one in stock. Don't lose it.