I have been told to let the truck idle for about 5min before turning off the vehicle. This is to prevent any bearing / turbo damage. Basically, letting the turbo wind down. Is this true? How do I tell when it has reached a certain temperature? Where is the gauge reading?

 

Thats about right if youre running it hard or towing heavy. Normal driving will be much shorter. My truck will cool down (to 350 deg. which is what I allow it to do) usually in under a minute under normal driving circumstances, some let it cool to 400. It really varies from person to person.

 

I don't have an EGT so I'm guessing but I had my auto start set to wait 1 minute 15 seconds prior to shutdown. Wouldn't want to hurt that turbo!

 

I've been told by the mechanic at the diesel performance shop that if you pull long and hard let it idle for a few minutes, normal driving should be a few seconds or so. I'm on my third truck 1 cummins and now my 2nd powerstroke and i've never had any problems. I pull a 33' gooseneck horse trailer about 14k in weight to go camping when I get somewhere I let it sit for 10 min. while finding the best spot to park.

 

Yes, you should let the engine idle for a few minutes after a hard run to let the turbo cool down. What you are trying to do by letting it idle is to let cooler exhaust flow through the turbo, which will allow the temperature of the housing to drop. You want that temperature to drop so that your bearings and oil lines cool off.

It goes like this: turbochargers spin pretty fast, and because of this they require pressure-lubricated bearings. This pressure lubrication is accomplished by having oil lines come up to the housing from the engine. Now, the problem with that is that you are going to put engine oil right next to a very hot chunk of metal. Given enough time, that metal will be equal in temperature to the exit temperature of your exhaust gas. When you've got the truck under a stiff load, that temperature climbs up into the 1000°F range. If you shut off that engine after a hard work, the oil quits circulating, and it is left next to 1000 degrees. That will cause the oil to burn, forming a film. This is called coking. Over time, that film builds up inside the lines and bearing journals, restricting flow. Before you know it, the turbo isn't properly lubricated, the bearings fail, and you find yourself cutting a hefty check to Henry Ford or your Friendly Auto Parts Store for a new turbo. Given that the turbos on here are VGTs, I'll bet the price is pretty stiff.

As a result, it is a good idea to let the truck idle down for a few minutes. Exhaust temperatures are much lower at idle than when the motor is under load (350°F Range), and if you keep that oil circulating as well, the turbo temp will drop pretty quick.

Unfortunately, you do not have a turbo temperature gauge from the factory. I'm pretty sure that the truck's computer has that data, but you don't have it shown on the dash. You can get that data by installing an EGT gauge, also known as a pyrometer. That is basically a thermocouple that is placed in your turbo inlet on the exhaust side. I am one of the folks who has hounded Ford for years to put a pyro gauge on these trucks from the factory, but this has been to no avail. Otherwise, you just give it a few minutes after a hard run and hope for the best.

 

Great break down. Thanks, I now understand completely

 

Cowboy Brett,

Thanks for such a thorough explanation. Like many other folks I had heard that the engine should idle for a bit before turning off the truck but never understood anything about the reasons why.

Now I want one of those gauges you are talking about!

 

Brett, very nice....thanks!

 

Wow, really good explanation. I've heard turbochargeres can spin at 100,000+ rpms so that generates heat which common sense told me to let it idle to cool off. But the rest of that I had no idea...

I'd like to suggest that that explanation find its way into the tech folder for any other interested or new user to see.

 

I'm not sure I buy into this completely. Although I know this is common practice for heavy machinery I've never really found a need to do it with light duty diesel motors - here's why:

Let say you are going down the interstate around 75mph with load, for argument sake even up a grade. You decide your gonna take the next exit. By the time you hit the stop sign at the end of the exit your egts are already gonna be pretty low probably at or below the 350 mark. The only way I think you could do any damage is to turn off the truck under load pulling grade and have some pretty high egt's to begin with. The dif being that big machinery (cats, etc...) hold quite a bit more heat becasue of the size and weight of the motor and actaully require this time to do what Brett suggested.