New day, new problem with my 1992 300D 2.5.


So, I was checking the condition of the glow plug relay yesterday, and when I pulled the cover off, I bumped into a solid brown vacuum line. It was so unbelievably brittle, the thing split right in half instead of bending. A quick search revealed the line came from the ignition shutoff valve - oops! So I threw out the short piece and tried to push the free end of what was left into the vacuum connector. It seemed to hold okay, but I was afraid it might back out with the engine running.


This morning, of course, when I got to work and parked, the engine wouldn't shut off. No big deal, I was half expecting it. I popped the hood and shut off the engine via the switch on the IP. I rechecked the brown vacuum line and sure enough, it was dangling loose.


Been looking through parts schematics but can't come up with a part number for this thing. Anyone know one? I guess I could just use a generic vacuum line, but I'd prefer to keep it original, if possible. Any tips? Also, anyone know the ID/OD of these things? I'm probably going to have to splice e new line into the original, since I don't want to go digging around behind the dash or mess with routing lines through the firewall.


Thanks!

I had this happen to me with the SDL recently (but with multiple lines!). The brown line behind the false firewall was still nice and pliable, but everything out in the engine bay was brittle. Touching it would cause breaks. I spliced in behind the false firewall on mine and have been fine since.

I recently redid all the lines in the engine bay and just used the heavier black line for the atmospheric vent for everything. It was the only line in the engine bay that was still in good condition, the fine lines all would break if you looked at them wrong. I redid several of the lines in the SL several years ago and used the smaller white line and they're getting brittle again. The black line will fit the vacuum fittings if you make it. It puts up a heck of a fight, but once it's connected, it isn't going anywhere!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I don't think mb sells the color coded vacuum lines anymore.

I recently ordered through the dealership and the vacuum line was clear.

your model/year may be different. I'm talking about '83 model year.

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1983 300CD Turbodiesel

MB dont sell the color line anymore, all they have is a whitish clear line sold by the meter. I would suggest you replace it all along where its brittle. And for marking sake for future reference print a small label and stick it as a flag on the line.

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

I just do not know what happened to Mercedes and quality. On my '81 300SD all the vac lines are original and as good as new - I mean no wear, no brittleness.

Blame the accountants.

I'd be willing to bet if you went out and flexed some of your vacuum hoses near the engine they'd snap.

The brittleness of the vacuum lines has nothing to do with Mercedes cutting corners or pinching pennies. It's a function of age and heat. Over time the plasticizers in the lines fail and they get harder and harder until they become brittle. Along comes your hand and "crunch", that's the end of it.

Could be like Ford in the 80s. Everything was black rubber and there were miles of lines. Talk about a nightmare to troubleshoot.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Those vac hoses were actually not made with much flex as far as I can tell; they are pretty stiff. Mine under the hood seem to be in good shape and I have unhooked them and rehooked them up several times in the last year while doing things like replacing the shutoff valve. Did not experience any brittleness at all. But I am also not going to test any of them either; leaving well enough alone.

There are many sources for the silicone vacuum lines in aftermarket. However, the color selection will be very limited. I've seen black, blue, red, yellow and white. From what I've read, the silicone lines don't suffer much from the heat. (I'm betting the yellow could be doctored to look brown.)

https://www.belmetric.com/oem-vacuumbrrubber-silicone-c-14_137/

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Sam

84 300SD 350K+ miles ( Blue Belle )