Boiling Coolant Expansion Tank

[Fawbs]

Ok just put a downpipe on with a cat welded into it, i have wrapped it in fibre glass exhaust tape to stop so much heat radiating from it as it doesnt have the standard cats heat shields. Since its been on only now and then the coolant in the expansion tank will start boiling and today some of it went out the over flow hole and leaked out the bottom of the car when i was at a garage. I had just topped it up though to the brim of the radiator, last time my coolant boiled the block was cracked however when that happened it really did boil to the point where u turned the engine off you could quite clearly hear it which is not the case at the moment. Just would like peoples opinions, should i be worried?

[Fawbs]

ok dont worry about this its sorted

[GTForbes]

what was it?

[Fawbs]

Well spoke to a few owners for a bit of camparitive servicing if you like. Basically cause i filled it to the brim when the pressure went up the rad cap opened and shot all the hot coolant into the the expansion bottle. I know when you fill the rad and expansion bottle up once you run it some coolant gets pushed out, i think its just cause its the first time i saw it happen on the road as i pulled up to a garage and seen red coolant coming out the bottom of my car alarms bells just went off. One guy said his radiator just finds its own level which is usually a few cm's about the first of the cooling fins when you look inside which is the level mine always sits at. I have a 40mm core aluminium radiator so it is usually about just under a litre down but it takes loads of coolant so everything is fine thankfully.