overnight -- trunk and fuel door work; door locks don't - Benzworld.org - Mercedes-Benz Discussion Forum

**holthoff** · 03-11-2007, 05:02 PM

My 240D has a slow vacuum leak which I'd like to track down. It's the typical thing where the door locks don't work after sitting overnight. However, this morning I noticed something further. Though the door locks had lost their vacuum, as usual, the trunk and fuel door actuators were still working just fine. Does this help to narrow down where the vacuum leak is coming from? Please let me know, as I'd love to avoid tearing apart the whole interior in my search for the leak.

Thanks,
Mark

diametricalbenz · 03-11-2007, 05:09 PM

It happens, I left my car at the Burbank airport for 2 days and all of the sudden everything starts leaking. Sometimes it's fine and others it's lost all vaccum in 3 hours. Start checking all of the lines in the engine compartment and then go from back to front.

**MBeige** · 03-11-2007, 06:58 PM

Yep, Mark, that's the only way. Open it up and see which one is leaking. Chances are it's one of the vacuum elements in the doors (3) or the master vacuum switch on the driver door. I've tried tracing the leaks on the wagon we sold and the connections on the floor remained in pristine condition, no cracks whatsoever. I guess being away from heat and mechanical use preserves them.

Does your 240D have ACC too? If so, check those lines as well. The climate control and central locking lines are all linked by the yellow check valve in the engine bay.

**holthoff** · 03-11-2007, 07:25 PM

Thanks, guys. I thought maybe I was going to get lucky there for a minute. I'll break out the Mighty Vac next weekend. But that brings up another question -- will it be tough to tell whether an element is leaking since the leak is so slow...?

**MBeige** · 03-11-2007, 07:34 PM

Yes, since your '80 240D may have the old style elements compared to the new style which has a rubber diaphragm inside that you will not see.

Then again it may just be as simple as a hose orifice stretched beyond specs and thereby allowing air to get in.

See this related thread http://www.benzworld.org/forums/w123-e-ce-d-cd-td-te-class/1248610-central-lock-vacuum-troubleshooting.html

This should be similar, I made this when I tried to fix the wagon's locking system

**holthoff** · 03-11-2007, 08:45 PM

Wow -- great diagram! Thanks. I'll report back with my findings. I'm betting it's a leaky diaphram in one of the doors...

-Mark

**ducatipaso** · 03-11-2007, 10:45 PM

sigh this is on my list of 'fixits' on the 280TE. I lose vacuum in just a few seconds. I think I know where the problem lies though because I can create different characteristics to how slowly it leaks out by moving around the left rear door. I have disconnected and plugged both the hatch and fuel filler actuators so I know it's not there... but I'd really like to get the hatch lock working again. What a PIA to get in there.

FratBoy · 03-11-2007, 11:02 PM

Using a vacuum hand pump is the best way to troubleshoot.

Disconnect the vacuum lines under the hood near the oil filter housing (on the diesels) behind the (yellow?) check valves, and try one system at a time to look for leaks. First doors, then climate control, then cruise, etc. If the situation fits, plug the offending system until fixed to ensure the ohters have enough vacuum...

FB

ddfletch · 03-17-2007, 07:41 AM

Yes!. Thanks fratboy. Sorry to jump in like this, but reading everybody elses problem fixed mine. None of my door locks trunk or fuel door worked. The reason being, none of the lines were hooked up. I just bought this 83 300dt and I get a new suprise everyday.