[lowrydr310]

I've been doing some cooling system repairs ever since I decided to change my oil filter housing gasket and ran into a few snags.

When changing the oil filter housing gasket, I removed the plastic coolant connector going to the head to access the lower oil filter housing bolt and it crumbled so I replaced it.

My car had green coolant from the previous owner. In November, the car had a new thermostat, water pump, and radiator installed, and was filled with green coolant, not by me.

I bought two gallons of genuine BMW coolant (blue) but before I use that I wanted to flush out all the green coolant. I drained the radiator and disconnected the hose from the cylinder head to thermostat, and more coolant came out of that line. I refilled with distilled water, drove for a few days, drained the radiator again and refilled again with distilled water, however I'm still seeing light green in the reservoir. It's diluted, but not pure water yet.

How many more drain and fills with distilled water should I do before it's ok to add the BMW coolant (diluted to 50/50 with distilled water of course)?

Also, last week I went to drive home and upon starting the car I got a low coolant warning. I went to top off and discovered that my cap was stuck. The top part twisted off but the core with the pressure valve and o-rings was stuck inside the reservoir. I was able to pry it out with two screwdrivers, and the coolant was definitely low. After topping off with distilled water and checking for leaks, I saw some drips coming out the bleeder screw. Like an idiot, I overtightened it during the last drain and fill and cracked it.

I got a new bleeder screw installed which doesn't leak now, however I can hear a very slight hissing from the cap after I park. It seems it's not holding pressure, however the level in the tank hasn't moved in a few days. But still whenever I go to open the cap, the inner piece is stuck in the reservoir and has to be pried out with a lot of force (not touching the reservoir, I don't want to damage that). This didn't happen before I switched to distilled water. Any ideas what's going on here? Old cap with bad o-rings?

I ordered a new cap and I'm waiting for delivery, I just don't want the new cap to get stuck and break.