My header tank has 2 bleeds on it. One come from the top of the rad and the other from the top of the thermostat housing. Now, i want to change my header tank to a clear on, the ones i have only have 1 small bleed on the top. If i T the 2 together will it be ok?

Should work as the idea is to let the air out so water can fill to the top of engine/ rad.
Put the T as close as physically possible, ie about an inch max.
Darren

That's what I've got, with a one way valve in the bleed from the radiator. Temperatures stable and not yet exploded.

Block the one on the top of the rad and just have the connection to the thermostat housing. This is how mine is and all ok.

As above Dan, i've blocked the bleed outlet on the polo rad on my zetec set up and only really use it if i'm re filling the water system to remove any air locks.

My running bleed is from the top of the thermo house to the to the header.

I have a pipe joining the two with a T to the header..

Previously I have just used the one from thermo housing with the rad one blocked.

Although the rad is lower than the water plain in the engine with the breather blocked it only half filled.

Both ways worked OK for me, just the rad fan used to come on more with the rad breather blocked.

Would recommend using both to make sure the rad is full.

Just remember to put the rad cap on and not drive 260 miles like I did last Sunday