Monovalve Rebuild
 

Since the OEM monovalve cartridge is now $130+ I decided to try the MTC cartridge but didn't have any luck, They would work fine under 2500 rpms but no heat at freeway speeds. I decided to disassemble the MTC and use the diaphragm to rebuild my oem cartridge. So far it is working perfectly. Video is below on the rebuild process.



https://www.youtube.com/watch?v=Znb_TLN7dqY&feature=youtu.be

Apparently, the spring in some aftermarket cartridges is too weak to keep the valve open in the face of higher coolant flow rates due to higher engine rpm.