I have my intake off, chasing a fuel leak, and have it soaking in the parts washer. I read somewhere about cleaning or checking the resonance valve....or something like that....

What should I do while I have the intake off....I already know I am going to have a hard time figuring out the placement of the vacuum lines.

Thanks
95 e300D

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

It's not that hard to check out the system and put it back together if you didn't take a picture before disassembly. First off check that the vacuum pots on the flaps hold vacuum and that the flaps open and close smoothly. If the flaps stick or move back slowly after releasing vacuum, clean them so that all the soot is removed and they operate freely. You can also check that the electric/vacuum switch over valve holds vacuum and that the valve switches appropriately when voltage is applied to the electrical contacts. As for reconnecting the vacuum lines .... I would suggest replacing them if they are old or cracked so that you are assured that they hold vacuum and will continue to hold vacuum for years to come. For reassembly, the intake vacuum ports on the switch are connected to the vacuum source and the right & left ports are connected to the vacuum pots on the flaps. If you have everything connected correctly the flap in the intake manifold (large one) should be activated at around 1,100 rpm and flap in the crossover pipe (small one) should be activated around 3,400 rpm. Both valves stay activated until the rpms drop off below their activation rpms.

Thanks for the info.....
I think I found my leak, so I am going to start the reassemble tonight.
I had already planned to replace the vacuum lines as they were all very loose.

These flapper valves, are they also called resonance valves? Could they affect performance if they are not working properly?

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

Most certainly driveablity can be effected if the three flaps are not working properly. The third flap is located upstream of the EGR valve near the airbox. Generally, I've found that flaps sticking open or "fluttering" can cause driveablity problems at speed such as surging or cutting out of power or both. In the 1997 models a feedback loop to the computer was instituted so that the computer knows if the flaps (intake & crossover) are are not in the right position and then a problem code is stored and the check engine light comes on.

OK, I tested the valves when I had them out of the intake, and they both work smoothly. However, when I re-installed and connected them, the small one seems to work at higher RPM, but was jumpy, the large one never moved. So I guess the electric vacuum valve is bad....or the signal going to the valve is not happening....how can I test this to confirm the problem?

Thanks

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

What triggers the change over vacuum valve? It is a mechanical contact somewhere? I guess since this is a 95 model, that it is not data sent from the computer. I need to make sure the valves are getting the signal to trigger.

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

The EGR box controls the flapper valves in the inlet manifold. - its the relay type thing with EGR written on it.

The functions are rpm dependant.

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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)

Where is the EGR box?

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

If you disconnect the electrical connections on the vacuum switch over valve and connect a voltmeter you should see a change in voltage when your engine gets to 1100 or so rpm for the large flap and around 3,400 for the small flap. Voltage should remain constant until engine rpm drops below the activation values. I doubt the electrical control circuit is the problem .... most likely it is the vacuum switchover valve itself. The valves cost less than $100 and I've had one go bad on me before.

Thanks, I was going to give that a try this weekend.

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

It may seem obvious ..... but just double check that you didn't install the switchover valve backward and that the exhaust ports on the valve aren't clogged with engine dirt/grease! Good Luck.

Exhaust ports on the valve?

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

There are three ports on the valve for each flap ... six total. Two intake (connected to the vacuum source) two control (switched vacuum connected to the flaps) and two exhaust (that allow atmostpheric air in to eliminate the vacuum when the flaps are deactivated by the switch). Exhaust probably isn't the techincial term but they function as a vacuum relief port so the flaps can be moved back by the spring to the rest position. The exhaust ports have the small section of rubber hose with a fitted internal screen.

Not sure I am following you. Are you talking about ports on the vacuum change over switch?

If so, there are 2 swithes bundled together, each one has 3 ports, the ones on opposite ends have what appears to be a vacuum source attached to them, and the one on the side is going to the resonance valves.

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL

On the picture below Ports 1 & 4 are "Y'd" together and appear to be a vacuum source. Ports 2 & 5 also are "Y'd" together. Ports 6 & 3 are going to the respective resonance valves.

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1995 E300 Diesel
1994 E320
1999 C230K
1994 S500 W140
1990 300 SEL