Hi All,

I decided to top up my coolant system expansion tank with extra coolant. I noticed that the the lower expansion bottle began to fill with coolant. I'm aware of the hose going from the top expansion tank to the lower one mounted next to the radiator so I avoided filling to that level.

How much pressure is the actual radiator cap supposed to hold before release coolant to the lower expansion tank? Should it pass on gravity alone?

 

The standard cap should take up 1.2bar.

 

Based on that then it must be passing. I'll get a spare CAP and have a play about to see if makes a different.