Intermittent coolant leak when car cools down??
 

This has happened three times since December turbo install. After the second time I've begun checking my engine bay/tray for leaks on parking the car. The third time it happened (shortly after the second occurrence), I saw no leaking in the engine bay when I parked the car and checked it. The next morning there was about 1/4 cup of coolant that had leaked out from under the hot side of the engine. On pulling the tray, there was no visible path leading to the source of the leak or puddling on components.

I'm thinking that the O ring on the pipe leading to the heater is leaking but can't figure why it would happen when the car is cooling down, rather than when hot and under pressure.

Ideas/suggestions? Thanks...

Honestly, look to see where it's coming from and trace it back. If you realy cannot find it then just put some dye in the coolant system and use a black light to see where it might be coming from.

It's probably coming from the lower rad hose. I had this problem and since there is suction on that side of the radiator, it only leaked when parked. Get some dye.

Because when you first shut the car off, the coolant temp actually rises (and so does pressure in the system) because the heat from the engine is still moving into the coolant, before beginning to cool down to room temp.

Thanks for the replies fellows. It looks like I'll need some dye.

Once I see the puddle under the car and pull the tray, the coolant seems to have already dripped/dried off the engine components making a simple visual trace next to impossible. I turned up my boost some today just to add some more heat/stress, but at this point...no leak today.

At least with the dye, it will provide a path to the leak even if it doesn't happen for a while. I'll report back the findings once I locate the leak. Thanks again.