2011 Dodge nitro SE 3.7L.

Unfortunately, no compression isn't related to any of the external engine components - this failure is internal to the engine .. The 3.7L engines have had some problems with exhaust valve seats becoming dislodged from the cylinder head which prevents the valve from closing and thus the reason for no compression.. This can be confirmed by removing the valve cover and inspecting valve train.. Your mechanic may have already discovered this issue.. Furthermore - due to this engines configuration - it may very well be more cost effective to replace the engine assembly. These suggestions I have made are based upon experiences i have had with the 3.7L SOHC engine.. Only through *hands-on* testing can these observations be proven to be the issues in your particular case. Good luck!