blackwolf wrote:

The Puma EGR coolers are not known for being leak prone, but it is possible. As your EGR is turned off in the map, even if the EGR cooler is leaking you won't be leaking coolant into the engine - and water entering the cooler will be on the exhaust side and will probably simply evaporate into the exhaust gas stream. If you had a catastrophic internal failure of the cooler it would be potentially very bad since coolant could conceivably enter the block through an open exhaust valve when a hot engine is shut off. I have never heard of this happening though.

Over the years I have on three occasions suffered from noticeable coolant loss from my '07 2.4: The first was due to a faulty expansion tank cap, it looked fine but I would loose perhaps 1/2" per week of coolant. A new cap cured this. The second was a leak from the water pump gland, this is really hard to spot since the pump is buried under the fuel pump and the gland drain is between the timing case and the water pump. A new pump cured this. The third was a minor leak in the original radiator, which was squirting coolant at the fan and dispersing it so effectively that you couldn't see any trace of it leaking (just like ARC99 above). This was actually spotted by my helpful MOT tester when it dripped on him during an MOT. A new radiator cured this.

To be honest if it really is only a minor loss then I wouldn't worry about it, I'd just keep an eye on it in case it gets worse.