The EGR valve on my 1990 300SE is non-functional due to a leaking (ruptured?) vacuum diaphram. Mercedes wants $400 for this baby, but it is available from Fastlane for less than half ($170). My question is why bother?

Will this affect performance or mileage of my vehicle? It doesn't seem to. However, I would think that the fuel injection system is expecting to see a certain amount of exhaust gas recirculated to the intake mainfold. I can believe that the vacuum leak could have an affect on other functions, but I have not noticed this either, and the line could be plugged easily. Is the intent that this function operates only when the engine is in a warm-up mode?

I would prefer to spend my money on other age-related and needed upgrades to this wonderful vehicle, but I feel the need to understand the function and effect before I decide to ignore it. Any help or advice you can give would be appreciated.

Thanks, Jon

Aside from reducing exhaust emissions ( NOx ), this valves serves another purpose.
When you re-introduce a small portion of exhaust gas into the intake system, it actually acts as an artificial octane booster.
Meaning, the air/fuel mixture becomes harder to ignite, therefore reduces pinging & also allows more ignition timing advance.
I have seen cases where a non-functioning egr cause pinging ( something you DO NOT want ), and also reduce fuel economy considerably ( because of the lesser timing advance ).
I would replace it.

__________________
2007 C 230 Sport.

If it's not an inspection item where you are, get a cheap one from a junk yard. Whether or not you install it, you'll have one ready in case you move or emissions testing comes to your area.

Sixto
95 S420
87 300SDL

Thanks guys. I will replace it and the used suggestion is a good one. I'll start shopping. There are no emission checks in my area, but it bugs me to know that there is something that is not working on the car.