Water pump mounting bolt feels wrong. (Ecotec)

(’07 Cobalt LS, vanilla 2.2, 70K mile)

Putting the timing chain cover back on. [1] One bolt goes through the cover into the water pump. Initially, it threads OK (not cross-threaded); But, when I get near (but still definitely below) the spec’d torque, the torque stops increasing, while the bolt continues to turn. It feels ‘stretchy’, like something bad is going to happen.

This looks to be an ordinary M8 bolt. Torque spec is 18 lb-ft. The water pump is probably aluminum.

I’m inclined to let it go where I am, around 15 lb-ft. But, it doesn’t seem like the spec should be anywhere close to a failure point. So, replace the pump?

Update: No problem: I just pushed through, and the torque came up to spec. My guess is it was flatlining while it pulled the middle of the timing chain cover up against the boss it sits on.

[1] After a timing chain problem. Nothing was done to the water pump or its bolts or its (separate) chain.