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  #1  
Old 07-15-2004, 12:22 PM
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Question Vacuum Modulator Connection

Thanks to this forum, I drove my '87 300TD last night for the first time since October of last year. Now for the question . . .

The transmission vacuum modulator has a single vac hose that plugs into a small rubber boot/connector. Mine is mostly gone so the tan vacuum line is not fitting tightly. Is there a replacement rubber connector (seems as if the one there would pull out and another press in) or must I replace the entire unit? Thanks.
Steve
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Old 07-16-2004, 03:11 PM
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This sounds like a two-bit dealership part to me...... the little rubber elbow maccaroni looking bit where vacuum lines conect to each other??
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Old 07-16-2004, 03:40 PM
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No. First, according to the schematic, it is called a "vacuum control valve" and listed as #65. I assumed this was an a/k/a modulator. Viewed from the left side of the engine compartment and viewing the side of the modulator, toward the bottom of that side is a rubber piece that plugs directly into the modulator. It appears that it was an elbow shape prior to being torn (assumption since it is missing part of the rubber where the vacuum line pushes in). Since my original post, I have replaced the direct vacuum line and instead put a barbed connector into the broken rubber. That allowed me to get an improved connection. I would of course prefer replacing the rubber piece if it is replaceable. Sorry I don't have a better description. Thanks for your patience.
Steve
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'87 300TD - 132K - Soon 4-Sale
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Old 07-16-2004, 09:56 PM
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I may get flamed here because I'm not an expert, but I have spent the last few days replacing all my vacuum connections (not the whole lines, just the connections) with silicone tubing. Go to the model airplane store and buy silicone fuel tubing. I've used it for years on various projects (including model airplanes) and have never had it rot, harden, stretch, crack, or loosen up. These are precisely the problems I found with the mercedes rubber. It's about .50 a foot, withstands very high temperatures and seals tremendously. You can put the hard line very close to the male connector and still make a 90 degree bend, no problem. I also used some vacuum grease on the exterior of the male parts to help seal things and allow me to remove the tubing if necessary. Otherwise it grips so tight you have to cut it off. This works for me.
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Old 07-16-2004, 10:41 PM
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Thanks for the tip.

I'm not familiar with the term "vacuum grease". Watzissit?
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Old 07-16-2004, 10:47 PM
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Vacuum grease is the lubricant / sealant used to seal the glass ball joints on moderate to large glass distillation columns and related equipment. This size and kind of stuff is used in research labs and small pilot plants.
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Old 07-16-2004, 11:24 PM
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The grease is not a necessity, I just had it on hand and liked the effect. I stand by my silicone tubing though.
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Old 07-16-2004, 11:43 PM
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Thanks for the lead I needed for the silicone tubing. I hit the local parts store this morning and tried to get some. Say what? I settled on some 3/16 rubber. It worked but I have a friend that owns a hobby shop. I'll try him. What size did you use?
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'87 300TD - 132K - Soon 4-Sale
'84 300D Turbo - 122K - Driving
'77 VW Type II - 77K - Restored
'08 250EX Ninja
English Bulldog (Brier) - My best friend. Passed away 12/02/04 while in my arms.
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Old 07-17-2004, 10:43 PM
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You know, I couldn't even tell you the size of the tubing. All those years of model airplanes, and I just looked and see if it fits or not. Basically there are two standard sizes, and either one will work fine, one being a little tighter than the other. Your friend at the hobby shop will know exactly what you need. It should be obvious when you look at it. Let me know how it goes..!
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