Coolant dripping out of coolant expansion tank

[snoopios]

Hi guys,

As the title suggests, I've got coolant dripping out of my expansion tank (the plastic bottle on the drivers side of the engine bay). I think it's been doing it a while because every now and then, I need to fill my coolant up because the car beeps at me.

I haven't had a proper check of the tank for cracks.

Does anyone know why it would do this?

Trying to not sound like too much of a noob but how do they work/what is the purpose of them in the first place?

I design central heating boilers for a living so I know how expansion tanks in central heating systems work; is it the same?

Thanks in advance.

 

[Nas80]

The problem is probably due to the cap being weak on the air seperating tank. But could be a dodgy coolant seal and the cooling system is pressuring up. You can replace the cap but first you need to wait till the car is cold and then open the filler neck on the front of the engine and see if you can see any little champagne bubbles.

I believe How it works is that as the coolant expands, the spring in the cap compresses and coolant goes down the pipe into the overflow tank.

When the car cools the coolant is sucked back in from the tank.

 

[snoopios]

Cool, I'll have a look.

I thought that was the way it worked but when I saw stuff about breather holes etc. I couldn't see how it was a closed system to do that.