They are safe at idle, but there may be an issue when your system is under load.
Seen as your chip is not overclocked, I would check that that Cooler is counted correctly { Check that the bracket behind the motherboard is straight and that the cooler does not wobble over your chip }
Also check that the pump and fans are moving okay.
I actually had a similar problem with my Corsair Liquid cooler, which led to a replacement. It is possible that something inside the cooler isn't working.
Also, what are you CPU temperatures under load?