I have a problem with my idler tensioner pulley bangs against the hydraulic pulley on the hydraulic pump when cold just started doing this . It bangs against the pump pulley for about 1/2 A minute and then every thing is normal till the next cold start I removed the belt and turn the pulley on the tensioner it spins freely both ways and it seems to have plenty of tension I turn the pulley on the pump it turn free and smoothly turning clockwise if I turn it counter clockwise it turns with a jumping movement not a roughness like a bad bearing but in a jump free jump free there is no end play and it is not noisy is this the way the pump is designed the tensioner was change three years ago has about 21000 miles on it.
The first time it happened it bang so hard at start up I figured it had dropped a valve or a rod but by the time I got to the back it had stop the next time again at cold start I had time to get to the back I could see the tensioner going back and forth hitting the pump pulley and then stop then the tensioner works perfect and every time I restart it runs as smooth as can be. This has happened two morning in a row the rest of the day the best.
My first thought is to change the tensioner but wondering if the jumping is normal for the pump. It's not a binding movement making me think it's normal
Not normal, When I changed out my tensioner pully I found that the 3/8" center bolt had elongated the mounting hole, allowing for a little slop in the mount when under tension. You would not notice this while the belt is installed, however when you remove the belt I was able to move the whole tensioner 1/16 to 1/8 of an inch. Which also allows the tensioner to run out of alignment, My cure for this was to drill out the mount hole, and the tensioner mount hole, to 7/16 and install a grade 8 - 7/16 inch bolt... no more wobble... ^.^d
We posted this 11 years ago on the Forum:
We replaced our two tensioners ourselves with new "sealed" Gates tensioners which are much improved over all other "open" tensioners. One new Gates tensioner doesn't hardly move and the other moves a little.
The hydraulic tensioner had a 1/8" flat spacer that I almost overlooked and if not re-used our hydraulic belt would not have tracked correctly. The spacer looked like it was part of the old tensioner could have been trashed with the old tensioner. I had to pry it off the back of the old tensioner.
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Replace the tensioner-- they do wear out. They not only tension, but dampen motion.
And verify that the pulleys are inline when installing.
Possible bad water pump, or what ever else is being driven by that belt. Won't be long before you find out what is bad.
It old runs the hydraulic pump of the Crankshaft pulley