Plastic cooling system parts can look normal on the outside, but what you can’t see is the plastic is getting heat stressed on the inside and can fail without warning.

This pair of heater fittings is from a 2009 Lexus LX470. The truck was in for normal service and I found a damp area near the hose that connected to the broken fitting in the image. I pushed on the hose to see if it was fitting loose, and the fitting broke apart with no effort. It was ready to fail, but from the outside it looked fine. Plastics older than 8 years of age can fail just like this part did. An engine for a Lexus is big bucks. A failure like this on the road, would lead to engine damage due to sudden coolant loss. HeyAnthonyAz.com