i pull up to where im going and i shut mine off. never any problems. i can pull 10-12k up a hill at 1250degrees, turn in my subdivision, make a couple turns, going the speed limit, pull in the drive, and shes right around 350 or so....i hear of all these guys having to let them cool for minutes before shutting them off, i have owned 2 cummins in the past 4 years, and have never let it idle for any period of time to cool...

 

might be why you've had 2 in the last 4 years

(sorry I couldn't resist, it's still early, I need my coffee . It seemed funny at the time )

 

I try to take it easy when approaching my destination, but always shut down when pyro gets down to 400F. Never had a turbo problem since I bought my truck in August of 04. I think you are wasting fuel waiting until 300F or less.

Waylan

 

I've had a 1989 that I put over 140,000 miles on, a 1992 that had somewhere around 148,000 or more (Boatnik's truck now), a 1995 that had near 100,000 miles on it, and my 1999 that has over 180,000 miles now. My sons truck had over 225,000 on it when he sold it. I nor he ever had a turbo problem shutting down less than 400 degrees. All of the stock trucks I ever owned never had a temp gauge on them so there was no way to tell what the temp was. Unless I missed it, there is no specific temp in the books anywhere, maybe a note to let it idle for a few minutes after pulling a load prior to shutting it down if I remember right. I usually coast into town and into the driveway and let it idle a minute or two once in the car port and turn the key. In my personal opinion, if you're waiting to get to 250 degrees, your wasting our precious fuel but that's just my opinion.

 

To each their own. I religously cool down. I have seen pre and post turbo temperatures increase after shutdown. Most notibly post turbo. It all depends upon the level of heat soaking prior to switching the key off.

Once on the dyno, I almost got heart palpations when they told me to shutdown, for the safety of the strap guy, after my second run.

For my part I think the 300F is just a thumb rule. I think it comes from the notion that dino oil used to like to coke up at around 400F. I am not sure about todays oils, nor synthetics.

But basically, if you are working the engine let it cool off a bit before shutdown. During those times, my turbo can can still be in the high 600F range. It can take a few minutes at idle to pull it down and get it to stay down after shut off.

Now if you are just delivering groceries, cooldonw is probably not required unless you were forced to stop light race a few ricers along the way.

If you have to wonder, take a cooky sheet and fill it to 1/8 inch with your engine oil. Turn your oven on full blast and let it heat up fully. Put the pan in the oven for 15 minutes and see what happens.

FWIW, typically industrial gas turbines typically have a 5 minute cooldown. Even when running high dollar synthetic oil and ball bearing bearings.

Jim

 

haha good one!! the real reason is because i blew up the auto tranny in the first truck i had, so i had to trade it for a manual.

 

I go 400 also. No problem --without a pyro you wouldn't know the difference and would do it. Neither Dodge nor Cummins thought it was important to make it mandatory.

My Perkins 105 HP in my Bobcat says to let the turbo cool 30 seconds and it would have been just running wide open -- I know its not a Cummins but the situation is the same.