1987 Peterbilt 379 arge air cooler repair

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by mile marker 27, Aug 30, 2022.

  1. mile marker 27

    mile marker 27 Road Train Member

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    ‘87 Pete 379. The charge air cooler has a crack on the passenger side, upper front side corner and the top bracket, that attaches it to the front of the radiator is broken. Im pretty sure all 3 of these can be tig welded and repaired. It was very easy to remove, so not a big job. After I repair the crack, I’ll air test it to look for other leaks. What psi should I charge it to? Another thing, are the charge air coolers specific to truck model or engine model? This truck is a very early ‘87 379 and was told(by Peterbilt) the radiator in my truck is a 359 radiator.
     
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  3. mile marker 27

    mile marker 27 Road Train Member

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    This crack is literally 3” long and 1/4” wide at the top 1”. I really don’t see how it ran like it did.
     
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  4. Animosus

    Animosus Heavy Load Member

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    I've always pressure tested at 30 psi and let it sit for like 10 minutes and see if it drops at all. The thought of the plug shooting out at a higher psi always scared me. Charge air cooler should be chassis side, so truck model.
     
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  5. lester

    lester Midwest's #1 Feed Hauler

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    Turbo moves a lot of air, so a crack won't really affect it that much. If I'm not mistaken even a new CAC has a spec of how much air it can lose under pressure and still be good. And it was more than you'd think. I'd pressurize it to what ever boost pressure you usually run
     
  6. mile marker 27

    mile marker 27 Road Train Member

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    I tig welded this morning, installed it and runs better in a pull.
     
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  7. 359 classic

    359 classic Bobtail Member

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  8. 359 classic

    359 classic Bobtail Member

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  9. lester

    lester Midwest's #1 Feed Hauler

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    Me too
     
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  10. mile marker 27

    mile marker 27 Road Train Member

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    This truck has really came alive. Seems to get a little better fuel mileage and smokes less. Gonna try and run the OH tonight, with the numbers Wore Out gave me.
     
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  11. mile marker 27

    mile marker 27 Road Train Member

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    What I don’t understand, is why this truck doesn’t have a boost gauge? It has a manifold pressure gauge but it stays very low. That gauge my not be working correctly?? I’d rather have a boost gauge. What’s the difference in the two?
     
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