Are you definitely getting more water? Getting the water out can be a bit frustrating as it takes a few changes to do so. Take a careful look via the dip stick to see if the level is actually going up. Since you did a pressure check and it passed the block and manifold are good. That leaves the water pump or the exhaust back filling.
Another note, did you run the engine up to temp when you did oil changes? If the oil level is not rising (the careful check above) it may be you are not getting all of the "oil" out. Just a tiny bit of water will turn the oil milky. I usually add a table spoon of liquid dish detergent as it helps to emulsify the water into the oil and helps in getting it out. I do this twice then add just the oil and run. The oil will often look a bit milky still and you will see condensation at the oil fill. I just run her for a couple hours at cruise speed and cook the rest of the water out and when it clears change and your good to go.
Dave Neptune
