[s-cars] Dodged another bullet or "Oh My!"

audijim at comcast.net audijim at comcast.net
Mon May 28 12:52:31 EDT 2007


I have something to confess, my S4 is a problem child. Over the past few weeks, I have been secretly stressing about a knock in my engine. I would start the engine in the morning and get a horrible knock sound what would go away as the engine warmed up. It was getting worse, and this holiday weekend, I finally had time to take a look at it. Actually, let me go back a week when I thought I had it diagnosed as a serpentine belt tensioner pulley that had a bad bearing. I ordered new stainless steel bearings from McMaster-Carr and they arrived Friday (hell, I ordered them Friday and they were waiting for me when I got home from work the same day! Unbelievably fast) Side note: looking at the pulley, the bearing does not look to be pressed in, it is riveted in place by the two halves of the pulley. I have a spare serp tensioner and before I replaced any bearing, I swapped on to the AAN, no change in knock sound! But while I had the tensioner off, I put tension on the belt with my h
 ands a
nd I saw the serp belt pulley portion on the crank pulley move! I found my knock! Some how, some way, the four bolts holding the crank pulley to the crank's timing belt gear wore away and the serp pulley started getting loose. When the tensioner was applying tension to the serp belt, it was putting force on the pulley and making a knock sound at the same time as RPM would on a single cylinder. I had a spare crank balancer/pulley assembly and installed. Check out the pictures on what I found. http://www.tdif.com/phpBB2/viewtopic.php?t=1432#13621


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