Nismopowered is right on with the "invisible" leak analysis. Since day one, I have had the smell of coolant in the air after parking my July '06 RAV (V6) in the garage after driving - I never found a leak, nor could I see one. Slowly, over a time frame of about a year and a half, the coolant level ever so slowly dropped down to the LOW mark WHEN WARM. Obviously, it would be below LOW when cold. All the dealer did was to add a small amount of coolant to bring to the proper level.
At just over the two year point, a different dealer (second) pressure checked the coolant system both when bone cold and when warm. Pressure check was perfect - no leaks were observed and the system did not lose any pressure. At this point the "consumption" of the coolant had increased, and the smell was still there after running the car, especially after highway speeds. Yes, the dealer had even asked me if it wasn't a sulfur smell instead of a coolant smell. Of course, big difference and I said "no way". However, I still didn't have any proof! Until......
Last month! Washed the car, and voila! While wiping down underneath the hood, I saw spray marks (individual spray droplet marks), pink in color on the right side of the firewall and (above) the underside of the hood. Of course, what could be doing that? The water pump (seal). I looked below the top right side engine mount (which appears to surround the top of the water pump) and saw a small area stained pink on a mounting bolt head. I hadn't been able to see any such staining before in this area; I believe that the leak rate had been so small that it instantly vaporized the coolant without a trace.
I took it to a different dealer (third) and they confirmed that it is the pump - didn't "need" them to confirm this really, but it is now official. Covered under the 5 year/60k part of the warranty. Further, the mechanic said that a different mechanic team there had just replaced a water pump on another RAV V6 with the identical problem. Also at this time the level when WARM was well below the LOW letters, so the loss rate has definitely increased. Dealer topped it off for me.
The dealer has ordered the pump (backordered, with no estimate of delivery) and also informe me that they have to pull the engine to make the swap. I will clarify this BEFORE work is started because to me it looks as if they simply support the engine (above/below), then they can remove the top right engine mount and IMO have access to the water pump. Have to wait for that.
Hope this helps those having the same issue, but maybe driving a newer vehicle. Mine has 37.5k on it to date. I still love the thing - best vehicle I have owned....did like my '98 Regal immensely, but I digress.