replacing plastic tubing in vacuum lines
 

greetings

re my '75 450SL, everytime I work under the hood I have to be real careful when nudging or moving any of the plastic tubes which carry vacuum throughout the engine compartment. heck, there's an almost 100% chance one will break if I attempt to move it aside to get to something else! So far I've been able to rejoin broken plastic sections with rubber tubing.

The plastic tubing has, over 25 years of heat in the engine compartment, become brittle and easy to break.

Does anyone in the forum know if it'd be ok to replace what plastic tubing I can reach with just regular rubber vacuum tubing? Or is there a particular reason why MB chose to use this thin plastic tubing, joined here and there by thicker rubber vacuum tubing?

Am talking basically of the plastic vacuum tubing that crosses over the engine itself where most of the heat is generated from both the engine and the catalytic converters which MB thoughtfully emplaced there.

Dom,

I'm pretty sure they use the hard plastic line due to it's durability. It will survive much longer than the rubber lines do. The lines on my car are a couple years older than yours and still holding up nicely, but then again I don't have a cat. You might see if you can get any of the MB hard line to replace your aged sections, just use the rubber lines as splices where the ends meet.

You probably could use the black rubber stuff to repair whole sections, but it'll break down quicker, plus the hard lines are somewhat color coded. On mine I have yellow, black and opaque, some cars also have green and brown as well, to help ID the various systems.

I just went through the same problem with breaking the tubing on my 85 380 se. I went to the mb dealer and bought six feet of the tubing (3.00) and replaced the most obvious and easy to get to peces first. Haven't had to replace the color striped ones yet but can't imagine the price to be that much more. Piece of cake job. Cut the tubing with scissors and you are on your way.

thanks for the replies Gents....

the durability of hard plastic vice just rubber lines makes sense to me...will check with the dealer today to see if he's got any in stock.

mine indeed has color coded hard plastic vacuum tubing and some of the opage stuff has line coloring as well....not sure I will try that hard to match it, just want to prevent easy breakage when working on the car and of course, vacuum leaks.

thanks again