1990 ford f150 xlt lariat serpentine belt

Chris Streett

Asked by Dec 28, 2015 at 06:25 PM about the 1990 Ford F-150 XLT Lariat LB

Question type: Maintenance & Repair

OK. You guys convinced me to stay original
with the belt although I don't agree with
some of what you say but we could argue
certain points all day. So you're the experts
answer me this. I replaced my water pump
and when I got back to putting the belt back
on it was very loose. Its a new belt and I
routed it according to the diagram. Why is it
so loose? Any answer you can give would be
appreciated. I've always done my own
repairs but this has got me stumped.
Thanks. Chris

4 Answers


The last 4 numbers of the belt's part number is the length. The first two, which aren't of concern here, just for future reference is the number of ribs the belt has across it's width. A belt that has part number 060808, for example, is a 6 rib width and 80.8 centimeters long. Make sure that the new belt and the old belt have the same last 4 digits on the part number. If you can't still read the part number of the old belt, measure it. Most auto parts stores have a belt measurer to size up the old belt. HTH. - Jim

1 out of 1 people think this is helpful.

Is the belt tensioner good? If the spring goes bad, or weakens, the belt will not be tight. Does it look like this? What engine.. the 5.0L?

1 out of 1 people think this is helpful.
Tom Demyan

I had to go a belt smaller when I replaced my Serpentine belt on my Mustang 5.0 as the tensioner was out of range. Just go back to the parts store and swap it.

2 out of 2 people think this is helpful.

Replaced a belt in an explorer (stock) and took the part number right out of the catalog. It was to short. Had to return to the store with the old belt, have it measured, and get one longer. The one that worked, according to the catalog, was the wrong belt. Could be a lot of reasons. Misprints in the parts catalog, even various size pullies being installed during manufacture.

2 out of 2 people think this is helpful.

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