A- Here is a simple step by step breakdown of how to replace the rear cam O ring seals on both V6 engines of the Montero Sport.
1) 6G72 3.0L V6- The passenger side rear cam O ring seal can be done quite easily from the top of the engine. All that is required is a 12mm wrench or 1/4" drive ratchet and socket to remove the two bolts that hold the "eye shaped" aluminum plug into place. Once you remove the 12mm bolts- twist and pull the aluminum plug straight out taking note of it's orientation. Once removed, clean it off with parts wash and replace the O ring seal with new one. For a longer lasting repair, add a small amount of silicone sealant (automotive grade RTV) on the aluminum plug where it will contact the flats of the cylinder head. Reinstall using the reverse procedure making sure to install it with the two bolt holes ABOVE the centerline of the plug.
The drivers side can be a bit trickier especially with 4wd (since the front propeller shaft can get in the way from underneath). The drivers head is much closer to the bulkhead (firewall) than the passenger side- leaving no choice but to tackle this job from below. The easiest access is from the front drivers side wheel well. More best access, prop the truck on a jack and remove the drivers front wheel- otherwise, leave the wheel on and turn the steering wheel to give you better access. Once the inside splash shield is removed, the plug is within arms reach. It will help if you remove the upper half of the transmission dipstick (remove dipstick, remove upper dipstick mounting bolts on the cylinder head bracket, and lower dipstick mounting bolt on the transmission) but is not neccesary if you have the patience. All you have to do is the exact same thing as you did on the other head- removing the 2 mounting bolts and removing the aluminum plug. When installing, make sure the bolt holes are BELOW the centerline of the aluminum plug.
2) 6G74 3.5L V6 - Everything above applies to this engine EXCEPT that since it is mounted more forward in the engine compartment than the 3.0L, BOTH sides can be tackled easily from above the engine compartment. The passenger side can be done EXACTLY the same as the 3.0L- while the drivers side can be done with the help of a small mirror or just by going by feel......either way, the 3.5L is MUCH easier to perform this repair on
Here is the driver side rear cam aluminum plug (that contains the O ring seal). Note that I have a manual tranmission with my V6, so the rest of you will have a transmission dipstick tube to deal with. This view was taken from underneath the truck- this plug can also be accessed from the side (through the fender well splash shield). The passenger side can be accessed from the top and can be easily seen.