Scored Serpentine tensioner pulley

Checksix · Post by **Checksix** » 23 Mar 2016, 23:19

As I was pulling into the garage tonight I noticed a slight "burnt rubber" smell. I opened the hood and noticed that the serpentine tensioner pulley has score marks matching the grooves of the belt (the belt looked fine). My 1st thought was the bearings had seized, but when I started the car the pulley rotated as it should, and seemed to be free. I'm ordering a new belt and pulley (I had just replaced both 25K ago) but to do otherwise seems foolish.

Anyone with a similar story?

Checksix

Post by **vtl** » 24 Mar 2016, 01:42

They all have marks.

Post by **vtl** » 24 Mar 2016, 01:43

Check alternator overrun pulley, it may be seized.

Post by **oragex** » 24 Mar 2016, 05:48

With the engine off, pull with a long extension ratchet 14mm socket to release the tensioner, then try with the free hand each tensioner, alternator and A/C compressor pulleys. Alternately, push on the belt to release some tension on it, then ask a bud to start the engine while looking at the tensioner. If it moves a lot when the engine is cranking it means there is a pulley about to seize. If the tensioner is about to seize, you can buy some time while waiting for the parts by removing it, removing the bearing plastic seal, then grease the bearings with bearing grease much like in this video

The belt might be fine, but cheap pulleys such as tensioner can fail in less than 20K miles. I put a Dayco timing belt kit 15K miles ago and the roller is already failing.

Checksix · Post by **Checksix** » 24 Mar 2016, 15:29

Thank you oragex for the suggestions. I did reduce the tension and rotated each part in the system and found they all felt correct with no sign of roughness in the bearings. Since I was there, I pulled off the plastic part and replaced it with the one I had pulled during PM at 150K. Before replacing it, I pulled the dust seal and re greased per your suggestion.

Now that I have the failed one in hand, the bearings on it seem just fine. My guess is the supplier used a cheap plastic that couldn't handle the heat. I've attached a picture and you can see the groves worn into the surface and where it had melted some. I sure wish I had kept better records from where I had bought this from, but unfortunately I can't.

While I see the one on there right now as a fix to keep driving until the new part arrives, I still intend to replace it with new.

Post by **oragex** » 24 Mar 2016, 17:30

Impressive, that pulley basically melted. I would think there is a pulley that is about to seize because normally the belt doesn't get warm or at least not hot when operating properly. Only when the belt starts slipping over a seizing pulley it will get hot because of the friction. Perhaps checking again the alternator pulley - it works differently than the other pulleys because it has a clutch. This video shows how to test it, only they guy uses a metal screw driver which is a big no-no because the alternator has charged cables when the engine is off. Instead, using a plastic piece should be safe

Checksix · Post by **Checksix** » 24 Mar 2016, 20:32

oragex, nice and helpful link on testing the alternator pulley, THANK YOU. I'll do that tomorrow for sure. I agree with you that it seems logical something has to be binding to cause this. After I replaced the bad pulley, the new one has been run about a total of 20 minutes without issue. Still there has to be something causing this. My guess is somehow it is intermittent.

checksix

Checksix · Post by **Checksix** » 25 Mar 2016, 13:07

oragex, I did the alternator pulley test this morning and everything looks good and felt real smooth. I used a Popsicle stick to jam the alternator in the back.