Q: Hi I have a coolant leak only seems to have when I remove cap it comes from underneath

The explanation for the drip when the cap is removed is that the cap seals the system and doesn’t allow the fluid to move. Think about it like this, when you put a straw in a drink, put your thumb over the top of the straw, and when you pull the straw up, it holds the liquid at the level in the straw. Then, when you remove your thumb, the straw is vented and the liquid is allowed to flow out the bottom. Basically, there is a leak in the system. It would be best to have a certified mechanic, like those available at YourMechanic.com, to pressure test the cooling system and identify where the leak is coming from.