MCI began installing Detroit Diesel S60 engines equipped with EGR valves, coinciding with the 2003 model change. Cut-in of this new engine is unit 55606 for the D4000/D4500 and unit 62098 for the E/J models.
A change in the compressor for the coach air system is included with this engine modification. Previous S60 engines were equipped with Bendix Tu-Flo 750 compressors, but for 2003, the compressor has been replaced with a model BA921 compressor, also manufactured by Bendix. This is a single cylinder compressor with capacity similar to the previous model, but it is not equipped with unloaders. This means when the air governor stops air pressure from increasing in the coach air system, and the air dryer is in the purge cycle, the compressor continues to pump air. This air flow is directed out the purge valve in the bottom of the air dryer. It is normal to hear air exhausting from the air dryer continuously during this time. The governor is also relocated to the vicinity of the air dryer; it is no longer mounted on the compressor.
The air supply for the compressor is no longer obtained from the engine intake manifold. On E/J coaches, the intake air for the compressor is received from the air intake tube between the air cleaner and the engine turbocharger. On the D series models, the compressor air intake has a separate air cleaner located forward of the engine radiator. This is a serviceable item and it is recommended this filter be serviced at the same intervals as the main air cleaner for the engine. Reference the MCI Maintenance Manual for this service interval.
Three G4500 coaches have been manufactured using a DDC S60 engine equipped with the EGR valve. All three are currently being tested by MCI Engineering.
If you need further assistance, contact the MCI Customer Support Center at (800) 241-2947.
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