radiator bleed valve stripped

I just went through this with my replacement engine project on my 2005.
After the 6mm hex stripped out , I used a flat blade screwdriver jammed in the hex slot and needle nose vise grips to break it loose.
The replacement bleed screw was only $6 at the dealer

 

Without risking damage to the radiator itself, you cannot get the valve out.

You CAN drive the car up on ramps to elevate the nose, higher on the passenger side would be even better to help. Then remove the RADIATOR pressure cap (cold engine) and insert a tightly fitting yet tallish funnel into the opening, adding fluid as you squeeze the upper radiator hose (about in the center middle of the forward underhood area) to try and force the air out. Once you get no more air that way, start the engine and allow to idle until hot. Refill as needed during this process, once complete allow to cool and refit the cap and top off the overflow to "full cold".

 

I did this with the radiator in its factory mounting location (utilizing the hole in top radiator mount)

 

Air trapped in the system.

When the coolant get HOT, it EXPANDS and should force some into the catch/overflow reservoir. As it cools, the coolant CONTRACTS and should siphon the coolant from the overflow back into the closed system.

Your system is remaining pressurized, at least slightly from the sounds of it, so you most likely have air trapped in it. Get the nose up!

 

Did this trapped air problem start after you drained and replaced the engine coolant or did it start out of the blue?

 

Some of the things I did to get rid or air:

Front of Prius was elevated
Ran engine with heat on full and radiator cap off
Cycled CHS pump in 15 second burst by jumping CHS relay contacts
Opened stripped/stuck radiator bleed valve

 

I only elevated the passenger side of the car and used the Lisle no-spill funnel.

 

Air is trapped in one place and that's the highest point of the system which is the cylinder head. Most new cars have the cylinder head higher than the rad. Its next to impossible to bleed the air out of this system properly without cycling the CHRS system. You will need to jump out its relay to start that pump motor while bleeding it or air will be trapped in that bottle. The rad is the least of your air problems.

Good test for air trapped is turn on the heat and listen for gurgling under the dash. If gurgling you still have air trapped.

 

Check out this link:
I just used a piece of copper wire instead of meter probes.
You are jumping the dark brass contact terminals of the removed relay

Changing engine coolant | Page 6 | PriusChat

video below:

 

I had to replace my Prius 2nd Gen Bleeder Valve because it was completed corroded and the 6mm hex key wouldn't turn it. I hammered a flat screwdriver into the old plastic bleeder valve and turned it counterclockwise to take it off. Here's a photo of the new parts (bleeder valve and O Ring), part numbers, and location of the bleeder valve.

 

Last Gen 2 I worked on had an aftermarket radiator that didn't even have the bleed fitting. Got the system refilled anyway, just took more patience. Longest part of the job was me going "why am I having such trouble finding the bleed fitting? Supposed to be right below this hole..."