Mercedes MBE EGR Cooler

The EGR cooler on this MBE 900 diesel engine developed a massive exhaust leak. The cause was the rear elbow at the cooler had worked it’s way out of the housing which caused the problem. This produced a lot of wear at the EGR cooler housing where the steel sealing rings sit. There’s not going to be a proper seal until the cooler is either replaced or repaired.

I voted for the latter solution since the core charge was $400.00 plus machining which is half what a new cooler costs. We have an extra one available to send out as well which we can keep on the shelf. Of course the exhaust leak that developed produced an engine code that derated the engine power.

This is common when a code develops…the engine drops off the horsepower to let the driver or technician know that if you don’t fix me I’m going to keep doing this to aggravate you to no end. It’s a simple trade off and very motivating to get down to the bare bones of the problem and figure things out.

These diesel engines do not like exhaust leaks because it reduces turbo boost and EGR efficiency. Of course the engine control unit is programmed to punish the operator if they keep on driving by reducing the horsepower significantly. The black soot mess an exhaust leak leaves all over the engine and firewall is an easy tell tale sign that the exhaust system needs attention.

The machine shop installed a sleeve in the bore of the EGR cooler giving it a new surface for a perfect seal. Once the technician from our shop reassembled the engine he went out and it ran like a rocket up a grade. The MBE diesels are 250 HP so we need every ounce of power we can get out of it. They have unit pump injectors with an engine driven fuel transfer pump putting out around 70 psi.

There are check valves that keep these pressures up and we have seen them fail (overflow valve) which reduces the fuel pressure and causes a power loss. The fuel transfer pump is a gear driven unit and I have never seen one fail yet. However if you see the fuel with a brown color coming out of the filters during a service it might be the seal in the transfer pump that is allowing engine oil into the fuel system.