How to adjust tension on Serpentine Belt

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letterman@invalid.com - 13 Oct 2008 03:29 GMT

1990 F150 with 302 engine.
It has that serpentine belt and I changed the water pump so I had to
unbolt the tensioner to get it out of my way. Now I wonder how to
adjust the tension and how tight to make it.
Anyone know?

Thanks

LM

PS. I wanted to check the clutch fluid reservoir. Cheap plastic cap,
it does not unscrew by hand. I'm afraid a wrench will break it,
besides that, maybe it lifts off or is childproof, or ?????
Anyone know?

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lugnut - 13 Oct 2008 16:20 GMT

>1990 F150 with 302 engine.
>It has that serpentine belt and I changed the water pump so I had to
[quoted text clipped - 10 lines]
>besides that, maybe it lifts off or is childproof, or ?????
>Anyone know?

It does not have a tension adjustment that you can do. There is an idler which
does not move and another that is spring loaded to apply the correct tension.
It has been my experience that the idler and tensioner bearing tend to go bad
about the same time as the belt. I always replace the idler and tensioner with
a new belt. They are not terribly expensive. I have replaced the bearing in
several of the idlers if they are metal - not plastic. The bearings are common
parts stock and should be around $5-6 each. You will need some sort of press to
replaced them. A 1 ton arbor press will do the job if you have one. Be sure
you stake them in place. Also, you should have a belt installation diagram
either under the hood or on the radiator header support. You will need a 1/2"
drive breaker bar or the special tool to load the tensioner spring and install
the belt. There is no adjustment required. Make sure the belt is properlu
aligned on all pulleys before starting the engine. It will eat a belt quickly
if they are not aligned.

Lugnut

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letterman@invalid.com - 14 Oct 2008 10:50 GMT

>>1990 F150 with 302 engine.
>>It has that serpentine belt and I changed the water pump so I had to
[quoted text clipped - 27 lines]
>
>Lugnut

Thanks for your help. My tensioner needs a 3/4" (or was it 5/8)
wrench to load it. Glad I did not need a special tool. I did find
out that a box wrench was not enough. I had to use a breaker bar.
Yes, there is a diagram for the belt "route" under the hood. I did
not replace the belt, it's still good. I just changed the leaky water
pump. I'll keep in mind changing the bearings when I replace the
belt.
I thought the bolt that holds the tensioner was tightened at a
specific pressure. I guess not. There is a little tab on mine and it
says "Range". I thought that was the adjuster.

LM

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lugnut - 14 Oct 2008 15:41 GMT

>>>1990 F150 with 302 engine.
>>>It has that serpentine belt and I changed the water pump so I had to
[quoted text clipped - 40 lines]
>
>LM

You must have used the idler pulley retainer bolt to rotate the tensioner. If
you look at the idler support arm between the pulley and the mount pivot, you
will see a 1/2" square hole intended to be used with either the special tool or
a 1/2" square drive. You may need a short extension bar in some applications.
You should not use the idler pulley bolt for this as it can either loosen or
break the pulley (sheave) bolt. IIRC, the pulley bolt is a left hand thread.
Congrats on getting the job done.

Lugnut

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letterman@invalid.com - 15 Oct 2008 07:07 GMT

>>>>1990 F150 with 302 engine.
>>>>It has that serpentine belt and I changed the water pump so I had to
[quoted text clipped - 50 lines]
>
>Lugnut

Hmmmmmmm
If it wasn't raining, I'd go outside and look for that hole?
I probably did use the pulley bolt.

There's a square hole under the bolt that holds on the whole assembly,
but removing that bolt made the whole idler assembly go airborne. (I
didn't notice the diagram and instructions before I started the job,
and after scratching my head for an hour, I just started to remove
bolts). But everything works, so I guess I did it right but wrong :)

Thanks

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Jeff Strickland - 15 Oct 2008 19:06 GMT

>>>>>1990 F150 with 302 engine.
>>>>>It has that serpentine belt and I changed the water pump so I had to
[quoted text clipped - 81 lines]
>
> Thanks

The arm of the tensioner has a square hole in it that fits the drive of a
1/2" Ratchet Wrench. You may find that a breaker bar is a more suitable tool
because of the added leverage, but the extra length of the breaker bar has
its own overhead that might make it a poor choice. I have found that the
tensioner is easiest to move from underneath the truck, but this means you
might need a helper to position the belt for you.

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