Deciding to replace a $3,000.00 turbocharger on a Mercedes MBE 900 isn’t an easy decision. This particular bus has been a thorn in our side for years mainly because of this one engine code that keeps popping up over and over again regardless of what we do to try and eliminate it.
This time we decided to go deeper and remove the turbocharger for inspection. So how did this all come about? The engine code is the dreaded 2631 turbo boost performance code. This means there is not enough flow and pressure in the exhaust system or the boost system to the engine intake to satisfy the on board computer parameter levels.
If this engine has any exhaust or intake leaks you’re about to be victimized on the road by the wrath of the engine computer programmers who made sure this bus would not sustain full horsepower if this code occurred and was not fixed properly. Back to the turbocharger side of things. I decided to go for it because this turbo is original and has just under 300,000 kilometers on it along with the engine.
It’s a lot of work to get the turbo on to the work bench but it was time to ascertain the condition of this component which is the work horse of all of the engine components combined. It rotates 100,000 rpms or more providing boost to the diesel engine determining how much juice it’s going to have to climb hills under extreme loads.
Once removed I looked up the factory recommended specs for passing or failing it for reuse or replacement. Expecting a dial indicator to check side play or end play all it said was to grab each end of the wheel shaft and push it evenly against the housing and check for drag. There was definitely some evidence of that but the main thing that stood out was the axial end play.
The end to end play was excessive with an audible clunk so off I went to order a new turbocharger. Another area that is crucial is exhaust leaks. The EGR cooler has an elbow at the back end that tends to leak and wear our the bore in the cooler. If that happens the cooler has to be replaced. I’ve been sending the worn out coolers to a local machine shop for repair inserting a bushing in the worn out end that was giving us the grief saving us at least $1500.00
I’m feeling positive that this will fix this pesky engine code for good with a steady and positive turbo boost pressure and perfectly sealed intake and exhaust systems. The expense is great but what do you do with a 120,000 dollar school bus? You fix it at all costs.
