Turning Engine Off

Discussion in 'Western Star Forum' started by CDLman63, Dec 17, 2020.

  1. CDLman63

    CDLman63 Bobtail Member

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    My instructor in CDL school told me that after running the truck "hard" on the highway, it is not good for the engine to cut it off immediately after stopping somewhere. He said to let the engine idle for a few minutes before cutting it off. How would cutting the engine off immediately after running "hard" on the highway, hurt the engine?
    Thx.
     
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  3. Numb

    Numb Crusty Curmudgeon

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    hot oil in the turbo needs to cool down, I believe.

    shutting an engine off after a hard run and they water is not circulating and cooling and they actually get hotter for a while.
     
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  4. rbrtwbstr

    rbrtwbstr Road Train Member

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    Well, Three Mile Island was running hard before it stalled and melted down.

    Ok, might be a bit over dramatic.

    When you're running, working the engine, it creates heat. Your cooling system circulates cool water to cool the engine. When it's hot, and you stop the coolant flow, the engine, (and the oil) that's still hot, will get hotter. Heat is no good for the oil, or the engine.

    With the newer engines that run hotter, it's even more important to let them cool a bit before shutting them down.
     
  5. Judge

    Judge Road Train Member

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    Cools turbo off, used to old rule was 5 minute warm up and 5 minute cool down.
     
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  6. Hulld

    Hulld Road Train Member

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    Shutting it off with out a proper cool down cokes up the bearings with burnt oil in a hot turbo.
    Usually safe for a shut down when the turbo is 350 degrees or cooler on the pyrometer.
     
  7. AModelCat

    AModelCat Road Train Member

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    Mainly for allowing some cool down time for coolant, oil and exhaust. If you've got a manual fan, turn it on while idling. Helps pull the heat out better.

    Idling also allows the turbo to slow down. Those suckers spin upwards of 80,000 RPM and are precision balanced. If you just finished working that engine and then shut it off, you'll likely be letting the turbo dry spin for a little bit. Better to let it slow down while still being fed lubrication.
     
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  8. LameMule

    LameMule Medium Load Member

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    Different metals cool and heat or expand and contract at different rates. Also important for the turbo.
     
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  9. pavrom

    pavrom Road Train Member

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    If he mentioned this he must be good ! Listen to him :)
     
  10. bzinger

    bzinger Road Train Member

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    893k on my isx turbo (2012) always cooled down .
     
  11. Doealex

    Doealex Medium Load Member

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    Agree with all the above and also heard that turbos don’t have bearings. It gets lubricatated by oil only (RPMs are too high for any bearing). As it spins fast when you shut your engine off quickly that turbine is still spinning too fast before it stops coking oil that left there leading to premature turbo damage.
     
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