Okay got the check engine light on my 98 ML 320. It is the EGR valve. So I pull it to clean it. In taking the intake hoses off to get to it I noticed a good bit of oil in the breather tube coming from the driver side of the engine. None in the tube from the passenger side. Is there a PCV valve or something in there that could be stuck open allowing oil to get sucked into the intake? Recently this engine has started using oil but the only thing is it only uses it if you drive a long distance at Highway speed 75+. Now in normal round town driving it will hardly use any oil in a 1k miles. But a trip from Atlanta to Nashville will use almost a quart. That does not seem like the ring coking issue. In my experience bad rings makes one use oil all the time. My guess is oil getting in thru the breather tube but I don't know how to stop it. I can't see anything that looks like a valve.

On a side note when I pulled the EGR the tube was almost completely blocked. Cleaned it made sure the valve plunger was free. Put everything back and cleared the code. But it came back about 3 days later. I now have a new EGR valve to put in this weekend if I can get the oil breather issue fixed I would like to do that as well while I have everything apart.

Thanks,

Replacing your EGR valve will probably NOT fix your problem. My 98 ML320 kept giving the EGR code after cleaning the egr Pipe as you did. I removed the electric blower unit on the front of the engine and I could see down through that area and there was a 6mm black hose that was off the intake manifold. You can't see the nipple, which is directly off the bottom of the manifold, center front. But you can feel it. You should replace all the 6 mm hose in that area as it will be cracked and maybe broken. The check EGR code is pretty generic and anything to do with purging the exhaust or mixing intake air will set the code. I have not set this code for nearly a year now, after replacing most of the 6 mm vacuum signal hoses front and rear.

Jim in Phoenix

Jim in Phoenix

Thanks for the reply Jim, I will look for any vacuum leaks. Did the vacuum leaks cause any other problems with idling or performance? I have chased vacuum leaks on other cars before and they can be tough to find. However they are generally causeing a drivability issue rough idle etc. My truck runs great smooth and no apparent loss of power. Just has the check engine light on so it was not making me look past the EGR valve.