This has probably been answered somewhere in the forum some place. Here it goes again: according to the owners manual you should wait 3-4 minutes after you have driven your truck hard and heavy before shutting it down. I think its so the oil lubing the turbo can cool down. I remember sometimes to let it cool and forget at other times. How much damage will it cause if any "I have Senior Moments now and then". I have a 1995 /4x4/diesel/ext. cab/ basically stock no serious mods but a K/N filter and air bags/ 103,000 miles on it.
Thanks

 

From http://list.priceweber.com/cummins/summer.html

Question: I tow a trailer during the summer. Is there any special cooldown needed?

Cummins Service Manager: If you are towing heavy loads this summer, you should let the engine idle for a three- to five-minute cooldown after extended full-throttle or high-power operation. However, under normal driving conditions like simple highway driving, a cooldown isn’t needed.

 

Thanks for your input "firebill," I am going to install a pyro meter, trans temp., and boost guages . I don't pull any heavy weight for a very long period of time,{4500# boat} according to Cummins service manager if your not pulling hard and full throttle for a long length of time and your driving the hi-ways without a heavy load a cool down isn't really needed. I don't mind waiting the 3 minutes in the truck when I do have a heavy load. I am retired and "have more time than money" cool--Thanks again:

 

The reason you don't shut it down immediately is to keep the dino oil from coking on the hot turbo shaft and to keep the bearings lubed as the turbo spins down (this usually don't take more than about 10 seconds though). If you run synthetic there is no coke, so supposedly there is no problem with that at any shutdown temp, but I'd rather take a minute or two and just listen to my Cummins growl as she cools down.
I have found that the 5" exhaust make my EGT's cool down over twice as fast as they used ot with the stock exhaust.

Chris

 

Stamey, The "synthetic" oils burn just like thier less refined origin. Synthetic oils originate from the same crude as regular oils. This thread proves the statement and the documentation links are there embedded in the articles. http://irv2.infopop.cc/6/ubb.x?a=tpc...2&m=3596097864

 

Ray thats not entirely true.....true group IV synthetics (yes I realize that there are only a handful) - such as Delvac 1 and Amsoil are derived from completely systhetic POA basestocks.

 

I, like Evil, have heard the same thing, and I use Amsoil, so that's where I come off stating synthetic does not exhibit the same characteristics. As said, supposedly. I'm no metalurgist or oil engineer. All I know is I have been running Amsoil in my gasser BMW for well over 100K with 25K oil changes and it burns no oil at all.

Chris

 

easiest way is to get a pyro and shut down at 300F

 

The PAO oils are derived from petroleum otherwise they can't be certified by the American Petroleum Institute (API).
In my work in agricultural research we developed an excellent canola oil based motor oil, good as most synthetics. Snag we ran into was API wouldn't certify it because it didn't contain petroleum. Since most vehicle warranties require the use of API certified lubes we were up that well known creek. API wouldn't bend it's petroleum only rule even after months of our "lobbying" efforts.
While PAOs aren't made in the traditional way dino oils are from crude they are made from chemicals that are derived from crude, in a sense they are still a petroleum product, just far removed from the goo that comes out of the ground.
And yes they do coke but at much higher temperatures.