Is the VCV responsible for anything important (besides EGR) on a 240D with a manual transmission? I've disconnected the EGR and thought of removing the VCV completely to store it safely indoors in the event that I need it for my second 240 with an auto transmission. Apart from plugging off unused vacuum forks, are there any special concerns involved in taking this off?

What year?

Early 240D no issue there. but I think later had some vacuum valves based on heat from coolant temperature.

You may need to reconfigure the vacuum system, if so.

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1983.

Yes, reading around the internet last night, I began to form that impression, but I can't seem to find anything definitive. Exiting the thermo vacuum valve on the block, there is a vacuum line that runs to a module behind the passenger-side headlamp, and then to the EGR. I've never known what that module is. There is a further line running from it into the cabin underneath the battery, which is perhaps a vent. I see on the diagrams of the vacuum system that there should be an electric switch-over valve between the thermo valve and the EGR, so I'm assuming this is it.

What exactly does this switch-over do? That's what I can't seem to find a clear answer to. I assume that whatever it does, it will require input from the VCV. So the reconfiguration would involve eliminating the 3/2 valve array on the valve cover, but keeping a line running from the VCV to the thermo-valve and then to the switchover?

I think most of what I am reading from you and my imagination are correct... based on what you're writing.

My preference is to delete all the emission functionality because its accepted where I live, especially due to the age of the vehicle. Please check that this wont be an issue for you.

If you can legally do so, then you can terminate the entire EGR vacuum supply system. That means, start at EGR valve, run backwards removing all the lines (or plugging them) so that no vacuum can be lost through the system via your modifications.

I agree, that line running into the cabin is likely a vent - is it solid black? the vent usually runs into the driver side under the gauge cluster.

check your passenger side kick panel for a plastic door - there might be an emissions control module there or behind the battery at the firewall.

look for

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the switchover valve should take information from engine temperature on when to activate based on rpm

but.. if there is an onboard computer - as I mentioned - then this would call the shots and tell the switchover valve when to activate the EGR.

Shortcut - if you can fined more than one temperature sensor (look on the head under the injection lines - possibly on the thermostat housing) that does not feed info to the A/C control unit - then you will know how your EGR is controlled. \
its either vacuum valve based on temperature... or electronic brains using temperature info.


best thing to do is print out a diagram and draw how you would cancel the system before getting lost in the engine bay

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You can block off the vac lines with a golf tee. While this could be temporary, I did this a number of years ago and have never seen the need to change it. And if you want to sell the car later, it would be easy to hook up the lines again just to make it stock.

I don't need the EGR on a car this old where I live, so anything related to the EGR can go. As I now understand it, the thermovalve sends coolant temperature information to the electric switchover, which then tells the EGR what to do. So all of that -- as well as the single 3/2 valve -- I believe, can be simply eliminated, with no re-routing necessary. And then the question is: does the VCV do anything else on a manual 83 240? If not, I want to take it off and preserve it (for my auto 240), and just cap off the unused vacuum forks (with a golf tee or what have you).