Drain cock kerfuffle
 

I have been running just water in my coolant system while I fixed my overheating problem. Fixed.


Now I'm flushing the radiator, and there's suppose to be two drain cocks right? One under the radiator (driver's side) and one on the back of the engine block.


Well I found both, and drained just the one under the radiator initially. Then I filled it with coolant and ran it for a couple days until I had time to do a proper flush.

So today, I go to drain the coolant... drain cock under the radiator spews green. Good.

Drain cock on the block comes out clear water. How is this possible? I immediately stopped draining from this location because I didn't want to drain something that I couldn't refill.
Is it not the same system?? If so, how is it possible that the fluid coming out of the block wasn't also green? I mean, I guess I suppose the coolant hadn't made it all the way though... I didn't drive it but 50 miles. But it's Austin Summer; it's hot. Is there a separate reservoir for the engine line?

No, it's all connected. If there was water against that plug then there must be at least a little bit of a dead-ended flow path there. still it's hard to believe that it didn't turn green.