Heard you don't need to let the 6.7 idol for a bit after driving. Is this true?
I thought you should let any engine with a turbo idol before turning it off.

 

Suggested cool down times are listed in the owners manual. My question is what is the real downside of not following these guidelines as I never let my truck cool down while idling since it takes 5-10 minutes?

 

well I know that my dad has an 07 5.9 and his turbo housing cracked and they said that it could be caused from exesive heat. but he also has a 40 ft. trailer hooked up every day. He never lets his cool down he just shuts it off no matter what.

 

The main reason for letting the turbo cool down is so the heat doesn't cook the oil out of the bushings on the turbo. If you havn't been working it really hard you're probably fine not letting it idle for a few minutes.

 

Was it a warranty repair? Or did they give him some story...

 

Allowing your turbo to cool down is only important if you want it to keep working
If your not pulling anything at least give it 30 seconds. I never shut off the key until I see 350 or lower on the pyro.

 

The water cooled variety takes less cool down time no doubt. I used to tell a guy here when he rolled up in his 2001 6 speed with a dual tandem goosneck hooked up and a big skytrack on it to at least stop before shutting the engine off. He would argue that "Oh I let it coast in", then he called me to put a new turbo on it, I did, then I put a new engine in it about 60k later. Cool down time is never a bad idea.

 

yes fixed under warranty

 

Sometimes you need more than a minute, even unloaded. Its best to get an EGT gauge and know when its ok to shut down.

 

This is a difficult one to answer to, exhaust housing 400+ degrees, oil that cokes into a hard ball of carbon after 270 degrees F on a shaft that turns 85,000+ rpm's= turbo destruction X $1500.00 to $2500.00 per turbo. Alternate method cool for 3-5 minutes = oil on shaft/bearings 270 F or less = oil that lubricates--- Cool!!. If you ever witness the leftovers from a violent turbo explosion from "coking" the oil and a broken turbo shaft the relationship between time (I cant wait) vs repair and operating cost of a 3-5 minutes per trip cool down time is drastically different. PK

 

it is VERY important to let your turbo cool down to at least 400 deg. you can get a turbo timer for about $100 and it takes 10min to install, or get an Edge like mine and it does it for you. shut the key off, get out and walk away, the engine will not turn off untill the egt's get to the temp you set it to. too easy and much cheaper than a new turbo

 

just like some have explained why you need to wait that has nothing to do with the temp of your egts. You are letting the oil/turbo cool not the manifold or engine but at least 5 min is the best.

 

i know it is the turbo/oil that you are trying to cool, but there is no temp guage on the turbo itself, the egts will give you a pretty good idea of the temp that the turbo is at

 

My turbo spins until it gets to a temp. safe to shut down. I can hear the whistle and watch the the EGT gauge to see the right time to shutdown. Mostly happens in regen mode.

 

I will try this again in layman's terms, OIL a carbon based substance starts to breakdown from heat at approx 268F (synthetic 400F) and reduces itself into a compound known as Carbon (black and hard). When the oil gets too hot from heat transfer of the hot exhaust housing of the turbocharger it "cokes" into this tar like substance just before it becomes hard Carbon. The Cummins diesel prevents this by feeding cool oil at 20-50 psi through the turbocharger bearing/bushing while the engine is running-hence the coolant fed oil cooler on the side of your engine. When the hot engine is shut down and the exhaust housing of your turbocharger exceeds the temperature that the oil can remain in it's original state (268F/400synthetic) it "cokes" into this lovely tar Carbon substances and siezes the turbocharger shaft to the bearing/bushing. You then start it up and try to drive away but the turbocharger impeller NO longer spins creating more additional heat and usually totally finishes the turbo off----- $2000.00++++. Carbon in it's raw form is an abrasive and that is why we have "oil" filtration on our Cummins diesels among other impurities. Simply put next time you have a camp fire imagine putting the black powder stuff off of a burnt log in your 70,000+ rpm turbo and think about how well it will lubricate the parts. If you cant afford the time to let your engine cool down or buy a shut down timer sooner or later you will pay for the turbo replacement. Clear like mud???? PK