Are most of you draining the block when you do a coolant change? My coolant looks really good, but is probably due. Those petcocks on the block look easy to use, but easy to break. Do they ever snap off? I don't think I need to flush much, just replenish most of the system.

 

They're pretty durable. I drained both this one and the one on the back of the block (thanks to TunedRX300 for locating the one on the rear for me).

 

And the one on the rear.