Mercedes MBE 900 Emissions EOS Code

This is a 2007 Mercedes MBE 900 diesel engine with an EOS electronic oil separator engine code. Once the separator has a restriction there is usually oil entering the intake and out the exhaust which of course is easily noticeable. Along with that an engine code will be indicated on the dash. The valve cover is integral with the separator and the only way to eliminate this problem is to replace the entire valve cover. This part isn’t cheap as you can imagine. However this diesel will never run correctly if this part isn’t replaced.

The separator is electrically charged to redirect the gases back in to the intake and the oil back to the crankcase. Once it fails the accumulation causes oil to enter the intake as noted in the previous paragraph. This is a common failure to 30% of our Mercedes diesel engines. It should be noted that this problem has only occurred to our rear engine Thomas HDX buses. The positive side of this failure is when the code comes up it states the EOS so you’re being told to replace the faulty component.

Since 2007 the Mercedes has had several issues adapting to different applications with the same engineering. School buses run at light loads on a split shift once in the morning and once in the afternoon. This causes a problem in most cases because of the lack of heat in the engine that is required to keep the emissions sensors, valves, injectors and heavy parts clean. I tell my drivers not to idle more than 5 minutes and keep the high idle on when the bus is stationary. 1200 to 1500 RPM is a good setting for high idle.

High idle helps engine warm up and creates more exhaust pressure through the exhaust system. Heat and pressure along with passive and parked regenerations in most cases will avoid trouble down the road. The main issue is the sticky tar like soot that covers everything in it’s path. Valves such as the EGR and intake throttle will eventually stick causing an engine code for improper position according to the on board diagnostic system. Any variance in the preset software parameters will create an engine code.

Over the years we have learned how to improve our maintenance avoiding engine codes. Right now we have one or two active engine codes way less than in the past. The regenerations are more frequent as part of the PM program. They are carried out by our techs by physically hooking up the lap top and the software. More servicing to the DPF diesel particulate filter has made a huge difference on the number of faults. It’s getting better over time.