So I added changing the heater valve out on my long list of while I'm in there things to do. I'm going with an all steel unit so my nice new clutch doesn't die a coolant death from a faulty HV.

Question is: how much coolant do I need to drain so I don't spill the coolant on top of my bell housing when I remove the HV hoses.

 

It tends to trap coolant so will probably leak some no matter how much you drain. Drain a few quarts and put a big puffy towel under there and/or have a shop vac positioned to suck up whatever comes out. Duck tape over the TDC site port is always a good idea when working in that area too. There's always something that might drop in... Good time to do those ground bolts too -- clean it all with baking soda and water and scuff up the contact points with a little emery cloth....