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Diesel cool-down cycle?

Discussion in 'Car Forum' started by Tennessee Slim, Oct 4, 2007.

  1. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    I just bought an Isuzu D-Max turbodiesel. There is no water jacket on the turbo, which put me to wondering. I had a Porsche 944 Turbo that did have a water jacket, as well as a pump that would keep the water circulating briefly after shutdown to prevent the oil in the turbine being cooked. Nonetheless, I habitually let it idle half a minute or so before switching it off, especially if I’d been rawhiding it.

    The D-max diesel has a sterling reputation so I’m guessing its exhaust is enough cooler than in a gasoline motor that coking is not a problem. So is it pointless to go to the trouble of an idle cool-down before switching it off?
     
  2. Toxie

    Toxie

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    Read you manual, it will tell you if a cooldown is required, but FYI 30 seconds isn't enough time to make an impact. You need to wait around 4 minutes at idle to make a serious impact on water/oil tempatures if you were "hotdoggging" it right before you shut it down. ANother FYI - most turbos today are oil-cooled, not water cooled. There should be an oil return line and it should have at least one oil-cooler attached to it.
     

  3. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Thank you for completely ignoring the question.
     
  4. knightkrawler00

    knightkrawler00

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    In six years of working on the Duramax, I've never replaced a turbo. I've heard of a few, but that turbo seems to be pretty bulletproof. A cool down probably won't matter too much in the long run. With that being said, it won't hurt either, and at least a few minutes would be preferred. I've seen exhaust temps hit 1300 degrees farenheight with no mods to the engine, aluminum starts to melt at that temp, and oil will definately coke at that temp. The biggest problem facing turbos is that the blades are spinning after the engine shuts down, after the oil pump quits supplying it with fresh oil, while the turbine shaft is hot enough to burn off the oil that is there.

    I tell my customers to not worry about it if you've been cruising around town, but to let it idle for a few minutes if they've been running hard.
     
  5. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Thank you, knightkrawler00. That was exactly what I needed to know. Neither the dealer nor the manual offered that sort of expertise.
     
  6. g29andy

    g29andy CLM

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    I have a pre-turbo egt probe in mine, and I usually let it cool to <300 degrees. However, this is usually only a few seconds to a minute, and that's after "spirited" driving. I do have a 4 inch Magnaflow exhaust, to that helps a little.

    Normal around town stuff, not at issue.

    Come on over to The Diesel Place, the GlockTalk of the Duramax world.
     
  7. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    Thank you, lovette, looks like I'm gonna have to memorize another user name and password. ;)
     
  8. Toxie

    Toxie

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    Uhhh. . .ok. Guess that your whole I-had-a-porche cooldown story didn't relate to your question at all. Moron. Thats exactly why people stop being helpful.
     
  9. Tennessee Slim

    Tennessee Slim Señor Member CLM

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    I s'pose if I'm that worried about it, I should invest in a cool-down timer. That makes more sense than always relying on my patience. BD Diesel Performance makes one for ~$150.