Engine radiator bleed valve leakage

Hello, I am new to the site, a fairly technical 'shade tree' mechanic type. Daughter has an '08 Prius, with almost 98k miles, dealer just did a warranty transaxle replacement. They also recommended replacing the radiator due to leakage, and we told them we'd take care of that ourselves if necessary. Upon inspection this evening after getting the car back, the only signs I could see of any leakage at all on the radiator (pinkish sludge) were on the drivers side around the bleed valve at the top to the right facing the front of the car. The bleed valve was closed, but not tight, and when I put my allen wrench to it, I got about 1/4 turn tighter, did not want to push it any more, for fear of stripping or breaking it, since it's aluminum. My question is has anyone seen a similar issue, or problems with this valve in general?
I'll be inspecting it nightly the next few nights after work just to make sure that was the issue, and nothing else is going on. Otherwise, it seems fine, smoother than ever with the new transaxle.

 

Thanks Britprius, will do. So far, so good

 

No leakage after several days, and radiator has remained full to the top. Happy campers!