Mercedes Diesel Engine Emissions Shop Talk

There is a substantial difference with emissions between 2007 diesel engines and pre 2007 diesel engines. Several add on components were designed to support the reduction of emissions. The older Mercedes in the video is your basic engine with turbocharger, charge air system and standard exhaust. 2007 required more emission reduction adding a diesel particulate filter, EGR valve, EGR throttle valve, electrostatic oil separator and extra sensors to monitor the system.

If the exhaust leaks or charge system is not to a certain level an engine code pops up indicating a loss in turbo boost performance. This code takes some repairs in order to eliminate it. For example if the charge air cooler is leaking the boost will decrease causing this engine code. This code helps maintain horsepower with these sensors so it’s a positive indicator to help the repair shop get the engine power up to standard.

So working with engine codes instead of getting mad is far better in the long run. They are there to help the technician fix defects especially on the emission side of the diesel engine. One thing we have learned in our shop is since exhaust is flowing in to the intake system there is a constant build up of soot and ash on valves and sensors and finally in the diesel particulate filter. That is why parked regenerations are important.

In a perfect world if engine temperature is maintained and there’s constant highway driving the emissions would be controlled to a decent level. The onboard computer monitors the DPF for restriction and heat which dictates when a regen is needed. Passive regenerations occur while driving instigated by the engine computer while parked regens are done with the engine software and laptop which takes around 30 minutes.

If there is no change and the DPF indicator light stays on the dash it’s time for removal and cleaning of the DPF. There are a few shops in our city that have the machinery to do this. The cost is around 400.00 (Canadian) and pays off considering the cost of a new DPF. With these Mercedes models we have been having good luck removing the filter and sending it out for cleaning without any failures. The turnaround is a couple of days.

Any restriction in the exhaust system of course causes a power loss and keeping these systems clean is a very important preventive maintenance procedure. It adds labor to the daily routine but definitely can not be ignored. That’s my take on emission controlled diesel engines.