Main vacuum line check valve 87 300D - PeachParts Mercedes-Benz Forum

dieselmania · #1 09-20-2014, 04:58 PM

So my engine would not stop and I discovered the plastic nipple on the main check valve where the key switch gets it's supply was rotted off. Anyone know where to get one? Seems like I'll need the main line as well as I may not be able to change the valve without cracking the original line, might try softening it first with a heat gun though. My other thought was to plug the hole where the nipple broke off and steal vacuum from somewhere else.

sixto · #2 09-20-2014, 06:26 PM

Yeah, cap the check valve and tap into the EGR or ARV lines since those systems should have been disabled long ago.

Sixto
MB-less

dieselmania · #3 09-20-2014, 07:52 PM

Quote:

Originally Posted by sixto

Yeah, cap the check valve and tap into the EGR or ARV lines since those systems should have been disabled long ago.

Sixto
MB-less

Yeah the vacuum line is still connected to my EGR but somehow a BB got stuck in it

. I'll tee into that. What is the ARV? Is that under the EGR?

tjts1 · #4 09-20-2014, 08:45 PM

Air recirculation valve is on the compressor housing. Basically a compressor bypass. You don't need it.

dieselmania · #5 09-20-2014, 09:18 PM

Thanks to all who are helping me so far, looks like I have a number of vacuum related issues. Tapping the EGR didn't work and checking the vacuum there I only have about 2 inches. Started checking everywhere and found no vacuum at the tree just after the pump. Traced it to the line that feeds vacuum to the transmission control and wyes off to the blue pot on the driver's side fender. Out of the top of the blue pot a rubber line feeds a black hard line with a blue stripe that heads down behind the IP and is clamped to a wire harness just before it disappears under the accelerator linkage. This is the line that is losing all my vacuum, I need to find out where it goes and what it does.

jay_bob · #6 09-20-2014, 10:40 PM

Sounds like the tranny modulator line.

Have a look here OM603 Vacuum & EDS Diagram

dieselmania · #7 09-21-2014, 12:23 AM

Thanks, great diagram. I did find the rubber line at the tranny completely rotted, replaced it and fixed my problems. I now have air flow out of the center dash vents..

. I ended up replacing all the vacuum lines, the short pieces on the tranny vacuum control valve wouldn't come off easily and I removed the valve to get a better look as I was afraid of breaking something. Now I will have to do the adjustment, looking at the book I'll need to run it up to full throttle.....yikes! Not looking forward to that!

sixto · #8 09-21-2014, 01:27 PM

You set the VCV with the pedal to the floor but with the engine OFF! You're not setting it to a vacuum reading; rather, the springiness when moving the VCV. Be very gentle with the bolts that hold the VCV to the IP. The threads in the IP case are very soft. Before messing with the VCV, see if you can hold some vacuum pumping a MityVac for all your worth with the throttle in the idle position. If it leaks faster than you can pump, the VCV might be shot and there's no point adjusting it.

The ARV is the device outboard of where the air intake hose connects to the turbo.

Sixto
MB-less

dieselmania · #9 09-21-2014, 02:53 PM

hmmmm.... I wanted to set it with the engine off but this is what led me to believe it is done with the engine running, from the FSM, last paragraph.

I haven't done anything yet, working on the central locking system today.

sixto · #10 09-21-2014, 03:01 PM

"Run" does suggest the engine should be running. Maybe someone has a German FSM to confirm. Regardless, there's no practical difference to this setting with the engine running or not. While you're at it, make sure pressing the pedal into the kickdown switch moves the bell cranks as far as they'll go.

Sixto
MB-less

dieselmania · #11 09-21-2014, 03:08 PM

Quote:

Originally Posted by sixto

"Run" does suggest the engine should be running. Maybe someone has a German FSM to confirm. Regardless, there's no practical difference to this setting with the engine running or not. While you're at it, make sure pressing the pedal into the kickdown switch moves the bell cranks as far as they'll go.

Sixto
MB-less

Will do, I did replace the plastic parts a few years ago.

dieselmania · #12 09-21-2014, 06:49 PM

After a test drive it looks like I won't need to adjust the vacuum control, it shifts better than it has in a long time, no doubt because of all the vacuum leaks! When I fitted the vacuum control to the engine I did try to get it exactly where it was before by the dirt marks.