serpentine belt slipped off, tensioner pulley ripped apart
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2006 w211 e350 station wagon
serpentine belt slipped off, tensioner pulley ripped apart
I've had 4 stored codes for a while now, I have been putting off fixing them because of the cold weather and the snow recently. I have a code saying my charge flap is jammed shut, so I ordered a new intake manifold which is on the way. my other code is for the coolant temperature being below temperature threshold. I ordered a thermometer to replace and today I was getting ready to leave to go to a family members garage to fix it myself outside of the cold. when I turned the car on to leave it warmed up and got hotter then it as been while I've been having this coolant problem the past couple weeks. I popped the hood and realized that the thermostat is missing the little plastic lock that's supposed to be on the wire connected to the thermostat so I figured that i didn't need to replace the thermostat and it was just the wire being slightly disconnected all along. so I took it for a drive to see if it would hold temp. as I was going down the road my power steering went out and my fans stopped and the battery symbol turned on on the dash. I drove about 2 minutes back with no power steering and looked under the hood and my pulley ripped itself to shreds, where the pulley used to be there is a stump that is just the center of the pulley around where it bolts down, inside of the engine bay there are shreds of pulley and sharp rings of pulley scraps scattered around. my serpentine belt is off but it is fully intact and all the pulleys spin that should spin. I don't know why this happened. was my tension pulley just old? can I just replace the pulley and not the whole tensioner?
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Joined: Aug 2004
Posts: 545
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From: Southern California
I think it is a combination of a worn tensioner and a worn belt. New belts are tight. Worn belts have been stretched in that position for a long time, and over many heat cycles it looses its ability to keep tension. Combine that with a tensioner that weaken over time, perfect combo for a belt to slip. The pulley should also be replaced. But should also check anything else that rotates to see if there are any loose/worn bearings or damaged pulleys.
Last edited by F1Fan; Jan 29, 2026 at 07:42 PM.
