When to close air valve for Highlander Hybrid radiator?

[paulri]

Doing a coolant drain & fill, I opened the petcock at the bottom of the radiator, and also turned open a similar-shaped valve towards the top of the radiator (a video said to do this, to release more air).

Now I'm closing everything up and getting ready to add coolant---at what point in the process do I close this valve--before pouring in the coolant, or after it is burped?

 

[paulri]

Well I'm thinking that the open valve would let more air in, so unless otherwise instructed, I'll close it off before adding the new coolant.

 

[mk378]

The top valve will let air out while you're filling. After it is full enough that coolant starts to come out the top valve, close it.

 

[paulri]

looks like I did it wrong (closed it just before I filled it with new coolant), but that's ok, I'm still burping it. I'll write that down for next time.

Originally Posted by mk378
The top valve will let air out while you're filling. After it is full enough that coolant starts to come out the top valve, close it.