W124: Vacuum Leak Under Battery Tray
 

I was cleaning up the battery tray in my 92 300TE, and found a vacuum leak that was well-hidden, but may be common to these cars.

Under the battery tray is a vacuum line that is only partially shielded by a black plastic hose. While cleaning out the accumulated crud in there, I noticed that there was an "unprotected" section of vacuum line (running into the battery area from under the wiper motor area to the fender) that had developed a 1mm hole in the side of it. I suspect that over the last 14 years, neglected batteries spewed junk down onto this vacuum line, and it eventually developed a hole.

Cut the vacuum line at the hole, and use a stiff wire to pull out the gunk that has gotten sucked in there. Use a 3cm piece of vacuum connector hose to reconnect the line.

I don't know which engine component uses this line, as it disappears down into the fender under the hood hinge.

Hope this motivates someone to clean out under the battery tray in a W124 (good PM) who is also dealing with vacuum leaks.

Chris did you take any pictures?

I would be interested in seeing whatthe hose and the area look like.

When I return from Santa Fe I may do the same with my 300TE (clean the battery tray area).

Thanks for the tip.

BTW, did you disconnect the battery?

I have to replace the battery tray and hold-down clamp still (corroded), so may be able to post some pictures soon when I install them.

You DO have to pull the battery and tray to see if you have this leak. It's a good time to clean out all the accumulated crud and look for rust and such...

Even though it looks like a vacuum line, it may not be. It may be the intake for atmospheric pressure for the vacuum system. There are several and at least one of them is located in that general area.

If that's the case, then it should be open to the atmosphere, and not plugged.