Testing Tensioner Pulley Spring (1 Viewer)


Oct 11, 2017
Pasadena CA
I'm working on fixing coolant leaks in my '99 LC. One spot is the lower radiator hose at the water inlet housing. I'm prepping to replace the drive belt (it's been dripped on), lower radiator hose, and probably the water inlet housing itself with a gasket and thermostat.

I'm also trying to figure out if I need to do something with the tensioner pulley spring. The alternator died a couple of months ago and I had a local Toyota/Honda shop replace it for me, and they noted that the serpentine tensioner spring was weak and might need to be replaced. They don't work on a lot of LCs. I'm trying to test that out to see if it's true, or if I can just replace the bearing.

The FSM isn't entirely clear on this. I tried pushing down on the belt per the diagram below, but the tensioner didn't move much. Not clear how to measure "pushing down" with 22# of force.


In another thread, @2001LC suggests testing it out using a wrench: "Very easy to determine. Using a 14mm socket with socket wrench or breaker bar. Turn the nut that retains the tensioner pulley CCW, just as you do when removing or installing the drive belt. You should feel a lot of spring force feed back."

Here's a quick video of me doing this. Gotta love the irony of coolant leaking onto the socket while trying this out.

I know the video doesn't really communicate how hard I was twisting (not too hard, pretty smooth)... but the pulley seems to spring up and down... though I didn't need to muscle it. The torque wrench was set to 22 lbf and didn't click. Any thoughts on whether it's operating as should be expected? Thanks!
Nov 4, 2007
Not new, but looks like enough tension. I say that because I see belt snap back in the idler pulley.

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