It's on an '83 300d, sits on top of the engine (on the valve cover, I think). Interweaved with the accelorator linkage. It's the vacuum control thingy that sets the pressure in the system. I believe it has to do with the tranny. Thanks!

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1989 300E 144K

Oh no....not this again!!

Some people say it controls the EGR.
Some people say it controls the transmission.
Some people say it does both.

My advice is to trace out the lines and see where they go. The black cover is only held on by 2 screws if I remember correctly. I believe the difference is the make and model of vehicle.

I always thought the transmission used the signal from those 3/2 way valves to replicate the vacuum signals that you only get on a NA engine. But....that's just my opinion.

Danny

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1984 300SD Turbo Diesel 150,000 miles

OBK member #23

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But my question is, what is it called?

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1989 300E 144K

The 617 service manual calls them switchover valves. Some of the parts catalogs call them 3/2 way valves. Their function is to operate the EGR valve depending on "throttle" position. On your model these valve do not operate the transmissison. But they will affect transmission operation if they leak. A leak robs the transmission of the vacuum it needs to shift properly.

That is the function of the vacuum valve on the injection pump.