LINK 4416206 - Caterpillar

plug block heaters can come loose because of incorrect installation. Use the guidelines that follow to correctly install either friction fit (drive-in type) or compression ring type engine coolant heaters.
* Use a file or sand paper to put an approximate 0.8 mm (.03 in) chamfer in bore for the core plug block heater.* Use ONLY antifreeze as an installation lubricant. NEVER use silicone grease or liquid soap or other lubricating fluid (other than antifreeze) to facilitate assembly.* Use the supplied parts with compression type core plug block heaters, such a lock rings, seals, etc.* Be sure all the parts are installed in the core plug bore in the correct order and position before tightening.* Use the correct installation torque when installing a compression type core plug block heater. Either too much or too little torque can result in a loose fit. Refer to the appropriate Service Manual module or Special Instruction for the correct installation torque.