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  1. #1
    FEP Senior Member
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    Default 3.8 belt tensioner

    How tight should the belt tensioner be in a 3.8 in an 86? I am used to the automatic tensioners or the alternators you pry over to tighten the belt. This jack screw style is new to me and I am unsure of how tight it should be. I am chasing a squeak and I am thinking it has something to do with this. I am putting on a new tensioner tomorrow.
    1986 Notchback, Recently repainted Light Regatta Blue(3J) and getting put back the way it should be. It had a 3.8 and a C5. Now it has a 5.0 and a T5.

  2. #2
    FEP Power Member Mustang Kid's Avatar
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    I think it has to be fairly tight against the belt. I'll look on my 3.8 tomorrow.
    -Sam
    1982 Mustang GL two hatchbacks, 3.3l and 5.0l
    1983 Capri RS Black Magic Ttop
    1984 Capri RS Sunroof
    1984 Mustang GT 'Vert
    1985 Mustang LX SSP CHP 8337
    1985 Mustang LX SSP CHP 8362
    1985 Mustang LX 3.8l 'Vert

  3. #3
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    I would really appreciate it. If you could show the belt deflection that would be great.
    1986 Notchback, Recently repainted Light Regatta Blue(3J) and getting put back the way it should be. It had a 3.8 and a C5. Now it has a 5.0 and a T5.

  4. #4
    FEP Member 83glxdroptop's Avatar
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    Personally I wouldn't get too exact with this. On my 3.8 I tightened it until I got about 1/4" deflection along the longest span. The real test in my opinion is when the car runs. The belt shouldn't slip under acceleration. As far as the squeak you mentioned, is it a squeak as in a bearing that needs grease or as in a belt that is loose? There is "belt grip" spray you can put on your belt to make it "grab" better.

  5. #5
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    I am pretty sure it is the bearing in the tensioner. I am going to swap it out shortly and see what that gets me.
    1986 Notchback, Recently repainted Light Regatta Blue(3J) and getting put back the way it should be. It had a 3.8 and a C5. Now it has a 5.0 and a T5.

  6. #6
    FEP Power Member Mustang Kid's Avatar
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    What is Deflection? Is that just how far you can push or pull the belt when installed?

    Here's a few photos. Not sure if this is my original or not, but it looks too good to be original.




    This is how far I could push/pull
    -Sam
    1982 Mustang GL two hatchbacks, 3.3l and 5.0l
    1983 Capri RS Black Magic Ttop
    1984 Capri RS Sunroof
    1984 Mustang GT 'Vert
    1985 Mustang LX SSP CHP 8337
    1985 Mustang LX SSP CHP 8362
    1985 Mustang LX 3.8l 'Vert

  7. #7
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    Thank you very much. That is about how I have it. Yes, deflection is the amount of movement the belt has. I put on the new tensioner and it still squeals. I tried a new belt as well and it is still squealing. As of right now I have swapped out the A/C compressor(I had one laying around), front alternator bearing(it had some slop in it), the tensioner and the belt. With the belt off the engine does not squeak, so I know it is an accessory. The P/S pump does have some endplay in it, but makes no sound when spun by hand. I really hope it isn't the water pump. That was put on by the previous owner before I got the car in February. The smog pump is already gone on this car.
    Last edited by Domino; 07-31-2012 at 02:11 PM.
    1986 Notchback, Recently repainted Light Regatta Blue(3J) and getting put back the way it should be. It had a 3.8 and a C5. Now it has a 5.0 and a T5.

  8. #8
    FEP Member 83glxdroptop's Avatar
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    Not trying to be a wise guy, but when it comes to "minor" noises from under the hood, my solution is to turn up the stereo. Tunes by ACDC seems to do the trick.

  9. #9
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    No more squealing! It was the belt the whole time. That is what I get for buying the cheap belt the first time.
    1986 Notchback, Recently repainted Light Regatta Blue(3J) and getting put back the way it should be. It had a 3.8 and a C5. Now it has a 5.0 and a T5.

  10. #10
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    Quote Originally Posted by Domino View Post
    No more squealing! It was the belt the whole time. That is what I get for buying the cheap belt the first time.
    What year is your car? Mine is an 83 and I have a new tensioner looking exactly like this, but websites and such say this new tensioner won't fit my car...

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