accessory belt still very loose after replacing alternator
 

Gentlemen,

I have a 2003 4.6 and just changed the alternator. I purchased and installed a new gates K070640 accessory belt from rock auto and correctly installed the belt only to find the belt extremely loose. Has anyone used this particular belt??? Or is it the tensioner that is shot???

I've got a different engine (M54), but assuming you bought the right belt, I'd double check the routing around all the pulleys. Somtimes there are different ways that it will route, and one is right and one is not right.

Step one is to compare old and new belt. You can measure with a string so you don't have to remove the new one. Make sure they are the same length. Then as suggested above your check the path. It took me a good 20 minutes to figure out the path on the M62 it's a doozy. There are a couple incorrect possibilities that will run all the parts but won't use enough length.

Basically most pulleys will have more than 180° wrap. If that's not the case you probably made a wrong turn

+1

When in doubt check with your measurements with Gates' website for length vs say Continental. Also confirm that the belt you received matches the sleeve part number your ordered. Seen this one also

Gates info
OE Comparison Rating OE Performance
Section K
Number of Ribs 7
Top Width (in) .947
Top Width (mm) 24
Outside Circumference (in) 64.64
Outside Circumference (mm) 1642

Continental
Belt Top Width (in) 0.965
Belt Top Width (mm) 24.511
Belt Effective Length (IN) 64.000
Belt Effective Length (MM) 1625.600
Number of Ribs 7
Belt Type Poly-V Belt

It always pays to double check

I was going to mention confirm part # accurate as above.


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The specs on the KO70640 I found via O'reilly's was an EFFECTIVE LENGTH of 1627mm. RealOEM specs the 4.6 with a 1623mm belt.

Gentlemen,

Thanks so much for the information. It seems that the continental belt is a 1/2 inch shorter than the Gates belt and to be honest that 1/2 inch might make the difference. and make it tighter on the pulleys... I cant measure the belt I took off as it snapped and melted around the crank shaft pulley.

1/2" is a huge difference in tightness but you may be able to make up for that if you didn't hit the limit on the tensioner


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Rule #1 in any car belt, use the dealer or OEM mfg belt. Aftermarket belt, even with 2-3mm difference, can cause a lot of issues (squealing)...

- For Honda, Toyota, I use Mitsuboshi belt.
- For European cars, Continental belt.