Coolant leak

[MattYD25]

I've owned my thai built 2010 d22 for just a little over a year now and suddenly I've sprung a coolant leak. It happens about once or twice a month and very randomly which is making diagnosing difficult.
The latest incident has me scratching my head as to whats happened but basically it wasn't driven for 3 days however on day 3 there was a random 500mls or so of coolant suddenly on my garage floor.

Has anybody else dealt with this before or have any idea on what could be happening?

 

[Old.Tony]

This is a very odd problem. If the vehicle has sat still for three days with nothing under it for the first two, then I can only think that:

1) Someone's playing games with you and putting coolant under the vehicle to make you worried about it. Check the reservoir to see if the coolant is any lower than before (take pics so you can't make mistakes).

2) Some thermal variation (eg cold night, warm day) is causing the problem. During the night as the radiator cools with the ambient temperature the liquid within cools too, and ought to draw some small amount of coolant back from the reservoir. During the day, the radiator (which is a respectable heat transfer device) heats up again and pumps coolant back towards the reservoir. This is where it might have a fault - say in the radiator cap, which may allow air to be sucked in as everything cools, but won't push coolant out (because coolant is a lot denser than air). This results in the coolant bottle filling and overflowing.

Have a check of the reservoir and see what the level there is.