Fred,
Here is a C13 Serial number prefix chart (generally used by Monaco):
Prefix: KCB
Model: C13 ACERT
Years: 2004-2006
Prefix: LEE
Model: C13 ACERT (regen)
Years: 2007-2010
The ‘LEE’ engines will have the ARD Head and other additional troublesome emissions devices.
Also, not sure which model coach that you are looking at but be aware that some 2008 and up Marquis and Patriot Thunder utilize a Chassis Control Module (CCM). You should research this, keywords are Kongsberg, Megatech, Mega Tech, Chassis Control Module, CCM.
Our 2006 Patriot Thunder has a ‘KCB’ C13 ACERT. We’ve had a few issues with it but nothing serious. Water pump (replacement is not for the faint of heart) and problems with the variable valve timing (VVA). As Fank mentioned, the C13 is quite thirsty, I’ve never seen better than 6 mpg.
I wouldn’t shy away from a ‘KCB’ C13, but only after a heath check by a certified CAT Tech. Include an oil analysis if the oil has not been recently changed.
-Scott