Coolant leaked from expansion tank?

[Fully Loaded Cali']

Just been for a 5 mile drive up the motorway, got back, parked van up and about half a cup full of water came out top of expansion tank?? So, tested - now been ticking over for 20mins. Rad hot, fan cutting in and out, water circulating (could see it through main tank) water level in expansion tank half way up over the filler cap where I'd expected it be. All ok now. What would have caused me too lose the water? System last filled last year and never had to top up? Only thing, the temp needle sits just over half way, been like it for the past year. Could of it been air in the system? Leaked out when the engine was switched off. Any ideas?

[Bubble Meister]

How did it get out of the expansion tank? The coolant system is sealed apart from the expansion tank cap that allows water in and out via the pipe to the top up bottle.

[Fully Loaded Cali']

Ah, no, there is a small spout on the very top with 3 vent holes. I'm beginning to think it was an air lock. The expansion tank isn't really that hot so don't think I'm boiling.

[RogerT]

Do you have the top up tank behind the number plate flap? Mine pi55ed water out regularly, until I realised I had a missing top up tank.

[Fully Loaded Cali']

Yes, this is the tank the water came out of. I'm thinking it's an air lock that's finally found its way out of the system. Its been a year since the coolant system was interfered with, I changed the coolant sensor, since then the needle has sat over the half way mark. It's now in the middle.....but I only had time to test it whilst ticking over for 20 mins. Fan cutting in and out. Wondered if anyone else has had this??

[kervinmervin]

It could be the dalek cap isn't fully working (on main tank), have you changed it recently? i had a similar thing happen, easy fix- hope that's all it is.

[Fully Loaded Cali']

Thanks, I'll beat that in mind. It's the original cap. The coolant has always sat high in the expansion tank when the engine warm then drops back when cooled down so thought working, but could be the first sign of it failing... Thanks for that.