Community Forums

Pexring · 08-02-2015, 05:27 PM

I swear I saw in the manual that came with my Newmar Dutch Star 2000 DP with a Cummins 330, that if I'm going to be stopped and idling for over 10 minutes, to shut off the motor. Yet I see semi's, especially during the winter, idle all night long. Do I need to be concerned about the 10 minute idle time? Maybe I need to go find and reread that section of the manual.

djbmsu · 08-02-2015, 05:38 PM

I am going to assume that you mistakingly read something incorrectly. There is a short period when you pull off the hwy to stop that you want to allow the engine to idle down before shutting it down but that mostly refers to newer diesel engines. You should have no concerns with a diesel engine in idle.

Wizard · 08-02-2015, 05:41 PM

There is a lot of difference between your Cummins 330 and those semi trucks. After a highway run you should idle for a few minutes before shutting down, however pulling into a rest stop, the pull in is usually sufficient.

Hit_the_Rhod · 08-02-2015, 05:48 PM

Extended idling will not have any detrimental effects on your diesel.

ga traveler · 08-02-2015, 05:54 PM

You read correctly. We used to get bulletins in our shop about excessive idling of diesel engines. As you said, do not idle over 10 minutes.It has something to do with oil washing off of cylinder walls. I also was told this by engine reps at the Louisville show.

lllkrob · 08-02-2015, 06:20 PM

As per the Cummins ISC Operation and Maintenance manual:

Idle / Warm-up / Cooldown

Excessive Idle

Should be avoided when possible. Results in
reduced fuel economy and increased engine wear.
An automatic shutdown feature is available. Contact
a Cummins distributor for details.

Engine Warm-up

Do not operate at full speed/load until coolant
temperature reaches normal operating range. Do not
operate above low idle until oil pressure is indicated.

Engine Cooldown

Prior to shutdown, an engine should be idled 3-5
minutes after extended full throttle or high power
operation. However, under normal driving conditions,
such as exiting a highway, engine operation is
generally lighter in nature and thereby, the 3-5
minute cooldown is not necessary.

waternut · 08-02-2015, 06:30 PM

All the engine manufactures want to claim the best fuel mileage for their motors. When you shut it down you don't use fuel. That said whenever you get ready to stop for more than 10 minuets let it cool down after a highway run then shut it off. Mostly protects the turbo.

KIX · 08-02-2015, 06:33 PM

Quote:

Originally Posted by ga traveler

You read correctly. We used to get bulletins in our shop about excessive idling of diesel engines. As you said, do not idle over 10 minutes.It has something to do with oil washing off of cylinder walls. I also was told this by engine reps at the Louisville show.

That's what I've heard several times from mechanics too

speed racer · 08-02-2015, 06:53 PM

After coming off the highway it's a good idea to let the engine idle for a few minuets to let the turbo cool down. It is lubricated by the engine oil and if you shut it down right away the heat from the turbo will turn the lube oil to a sludge and in time will distroy the turbo from lack of lubrication.

Pa Miller · 08-02-2015, 07:10 PM

Get a ekg temp gauge and when it gets below 300 degrees shut it off...or turn on the high idle switch .

koda59 · 08-02-2015, 09:29 PM

When you see the truckers idling all night, they have put the engine into high idle.

Skip426 · 08-02-2015, 09:45 PM

Quote:

Originally Posted by koda59

When you see the truckers idling all night, they have put the engine into high idle.

AND are sleeping in the back, with either heaters or A/C running for their comfort.

Coaches have furnaces or gen sets and roof air for that.

38Chevy454 · 08-02-2015, 09:46 PM

Most all newer turbo diesels have water cooled turbos now, which greatly minimizes the oil coking that old turbos had. As stated, just the coast down off the highway is pretty good to cool it down. Couple minutes idling is more than sufficient for cool down.

Truckers do have a high idle setting they use, to keep enough heat in the engine. They may have an APU (auxiliary power unit) setup that allows then to run the A/C or heat and then they can shut off the engine. But extended idling at low rpms is concern as it does cause more wear. Refrigerator trailers have a separate small diesel engine for the compressor, and they will start and run on and off automatically. They are louder than the engine or the APU. Don't park by a refer unit if you can avoid it.

Skip426 · 08-02-2015, 09:55 PM

Quote:

Originally Posted by ga traveler

You read correctly. We used to get bulletins in our shop about excessive idling of diesel engines. As you said, do not idle over 10 minutes.It has something to do with oil washing off of cylinder walls. I also was told this by engine reps at the Louisville show.

100% Correct.

As a turbo charged diesel engine cools, the pistons and rings shrink away from the cylinder walls , resulting in excess clearances, and as the combustion chamber cools diesel fuel combustion becomes less complete, resulting in un-burnt fuel washing combustion chamber carbon down past the rings into the engine oil ( it's that carbon that makes diesel engine oil so black) so the less time your diesel runs below full operating temperature the better.
That includes start up time too.