Why does my new belt look like this?


Old 10-29-05, 04:03 PM
Bill W.
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Why does my new belt look like this?

Chances are I worry too much but I have to ask. I just replaced the accessory drive belt, a one piece serpentine belt, on my 2001 Ford Escort ZX2. I spent the extra money for a Gates belt rather than the discount brand. The tension is not adjustable being an automatic tensioner. It took a couple of tries to get it installed properly but I can see there is only one way you can really put it on with the grooved pulleys contacting the ribbed surfaces and the flat pulleys on the smooth side.

Anyway the car runs fine, no noise, no problem. My question is that after about 20 miles I looked under the hood and observed the flat side of the belt is now discolored and bears markings that appear like lines running lengthwise. The smooth surface still feels smooth. I instantly wondered if the belt was too tight and wearing out rapidly so I checked the thickness with my micrometer and came up with about 170/1000 versus 162/1000 for the 40,000 mile old belt I replaced. I can see that the flat pulley at the top that contacts the flat side of the belt was originally coated with a black paint which has partially worn off and Iím guessing that imperfect surface could be leaving an impression on the new belt.

Is what Iím seeing normal? Do you see the same thing with your new belts? As I said it is a quality belt, Iím sure itís installed correctly, and it operates noiselessly. Thanks in advance for your time and knowledge.
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Old 10-30-05, 04:38 AM
the_tow_guy's Avatar
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As long as all of the pulleys are in good working order, especially the tensioner and idler pulleys, I don't see a problem. We tow an awful lot of vehicles where the owner replaces a serpentine and shortly thereafter it spits the belt, often ruining the belt. Cause: One or the other of the tensioner or idler has a bearing going bad which misaligns the pulley with the belt. Not a bad idea to replace both pulleysa when you do the belt. The paint on the metal pulleys rapidly rubs off and leaves a shiny surface where the belt runs.
Old 10-30-05, 12:51 PM
Bill W.
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Thanks for the info tow guy. Now that I shine a light down and study the lower idler pulley which has lost some of its black factory paint I can see that the pattern on the back of the new belt looks like that on the pulley. My guess is that the Gates aftermarket belt is a few thousandsth's inch thicker when new than was the original equipment Motorcraft belt, hence the impression made by the idler pulley. Thanks again.

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