Car is a 98 E300D. What is an ERG valve, and what causes it to get clogged. Can running the engine with it clogged cause any damage? And, generally, how often does it clog and have to be replaced? Thank you....RSL007

I Think you mean EGR valve not ERG is that correct? The EGR stands for Exhaust gas recirculation. I am just a parts guy so what the fuction and cause might be I don't know. I did look it up in the film on your car and your car has it built into a exhaust line. I have a picture here if you would like it faxed to you just e mail me your fax number.

It is called an EGR valve
 

which stands for exhaust gas recirculation. Cars in the US have had this device for quite a number of years. It allows air from the exhaust manifold to flow into the intake manifold which is supposed to reduce the amount of NOX (I think) generated during the combustion process. Over the past few years industry has started doing the same thing on steam boilers to reduce the NOX emissions. It actually has a "cooling" effect in that application and you set it up based on exit gases O2. I know that the EGR valve is controlled off of vacuum but am not sure how it knows what % open to put the opening of the valve. Someone else will have to explain that.

Race cars and vehicles in Europe do not have this device.
I would advise keeping this system in working order on the late model diesel. Just clean everything up. It will more than likely plug again.
Jim

European MB models suffer from this EGR valve since about 10 years now and I think that the % of opening is determined by the O2-sensor and the pressure-sensor in the air intake.
Since I didn't want my car to mess up the entire air-intake system I dismantled the EGR valve 280.000km ago...so the engine in my car doesn't have to bite its own dust anymore...

greetingz,