The turbo can be very hot after making boost. The exhaust temp at idle will cool the turbo so you do not coke the bushings.

Any time you shut down, the oil flow stops. If the turbo is too hot, you will coke the bushings and lead to turbo failure.

I think the Cummins is capable of having low cylinder temps in truly cold weather (not like I know cold weather in Alabama) and the cylinder can build up deposits from unburned fuel.

Does all that help?

Ronnie

 

With my trucks, once it has oil pressure, its ready to be driven. It won't get warm by idling. Most that I let it idle is to scrape the windows off and get the snow off the truck. I don't have that auto tranny issue though. Letting it idle for 20 or 30 minutes won't help anything, even in the real cold.

 

i leave my truck running all the time...people hate it! but if its really cold ill let it run while i go eat or shop, pretty much anything that requires me to start it again within 30mins ill let her run.. even during summer.... just habbits... also i let it run all night when im at rodeos sleeping in the camper running off the truck.. when cold in the mornings i let it warm for 5-20 minutes....

 

Great replies! I definitely wouldn't have known a number of these points. Especially about putting the 727 into neutral if I want to circulate the fluid.
S.

 

Over here on the left coast we call the results of extended idling "washdown".
What happens is at idle not enough heat is generated for complete fuel combustion. The unburnt fuel washes the lube oil off the walls of the cylinder, not good.
Some unburnt fuel gets past the rings and starts diluting your motor oil.
On some over idled engines the oil level will go actually up with the addition of the unburnt fuel.
All and all not a good situation.
I wait till my oil pressure comes up then drive easy for the first few miles.

 

My current truck will never see cold weather, but my 1991 saw lots of it. It was a 4X4, 5 spd. In really cold weather, I put a sheet of heavy cardboard right against the rad with an 8 inch hole in the middle. I would always plug in the block heater when temps got below -10 C., and used 0/30 semi/synthetic oil in the crankcase. In -25 C or lower, I would place the T-case in neutral, and put the transmission in 4th gear, than let it idle for 5-10 min. at the most.
with the cardboard, the motor would warm up much faster, and stay warm in stop and go traffic around town. If you travel at Freeway speeds, you would need to remove some or all of the cardboard, especially if you are towing. I ran the truck this way for 10 years with no problems.
If you are not able to plug in the block heater, running 0/30 oil, will really help with the startup, on a real cold morning.

 

Especially because I have large injectors, I get moving as soon as I have oil pressure. It's of prime importance to get the RPM up and get temp into the engine ASAP.

If you have oil pressure, you have all you need to run higher RPM, so get out there and DRIVE IT. I wind out the gears until its up to temp and don't shift until 2500 rpm or so. This extra rpm raises EGT and also helps a more complete burn for a given amount of fuel.

Babying an engine from a really cold start just prolongs the cold operating conditions that you want to avoid.

Now-- I wouldn't go put a heavy load on a stone-cold engine. I'm not talking about a huge thermal shock going from cold start to mega-loads and redline EGTs.

I'm just saying that the higher the average temperature, the better.

Justin

 

Run 5W40 synthetic or at the very least 10w30 when it's cold. 15W40 is like molasses when it's truly cold.

EGT's take no more than a few seconds to hit below 300'F when it's real cold out. No real need for a cool down.

I don't believe extended idling is good, let 'er run for a few minutes then gently drive away for the first few miles.

If you're not pulling anything, you can block off the whole rad, just slide cardboard in between the intercooler and rad. Some around here have even removed their fan with no problems, in the winter months of course and not towing.