Timing belt tension spring's purpose AFTER belt install?

[Allen McCready]

I have two sets of instructions for changing the timing belt on a 97 camry le, 4 cyl. Both say to torque the timing belt tension (upper) idler pulley bolt to 31 ft-lbs, after installing the timing belt and just before installing the upper timing belt cover. However, doing so, appears to freeze the belt tension applied by the spring. I thought that the spring was to continuously apply tension to the belt and dynamically adapt to operating conditions, particularly belt wear.

Is the upper idler pulley bolt supposed to stay torqued? If so, doesn't that mean that the spring has no effect other than to position and freeze the upper idler pulley at the timing belt's installation time?

I am leery of leaving the spring "out of the loop", but both sets of instructions appear to say to do exactly that. Obviously, if the bolt were left loose, it and the idler pulley could at the least rattle, and at the worst eventually allow the upper idler wheel to fall out.

[Brian R.]

The instructions are correct. The spring just positions the pulley. The belt doesn't stretch. If it did, the cam and ignition timing would change - bad for the engine.

[Allen McCready]

That's exactly what I wanted to hear. Now I can quit worrying about having to do this job again in a few weeks or months.

Thanks.