I periodically read a thread that relates to an engine that idles too frequently ( an unknown amount of times ) and not run at highway speeds is not a good idea. But .... I never read the mechanical reasons why. I usually start and let my Cat 400HP run for 30 minutes every 2 weeks. Mostly the thread answers are: it's the oil that doesn't have the ability to lubricate correctly or something relating to ???? Anyone have the facts? Just the facts Mam, as Sargent Friday would say.

2ndhom wrote:I periodically read a thread that relates to an engine that idles too frequently ( an unknown amount of times ) and not run at highway speeds is not a good idea. But .... I never read the mechanical reasons why. I usually start and let my Cat 400HP run for 30 minutes every 2 weeks. Mostly the thread answers are: it's the oil that doesn't have the ability to lubricate correctly or something relating to ???? Anyone have the facts? Just the facts Mam, as Sargent Friday would say.Diesel engines will not reach operating temperatures when sitting at idle.Most diesel vehicles have the ability to raise the idle of the engine by using the cruise control. Even my F350 Power stroke engine will automatically raise the idle if sitting still and in park (the ECM does it). My American Dream has the ability to raise the idle with the cruise.If you are starting your engine so that it does not sit all winter the 30 minute time range is ok, but raise the idle to 1200. Other wise it is best not to start it.

Your engine will not get up to operating temps. This is very hard on the injectors for one. The colder temps inside the combustion chamber cause the fuel to cause build up on the tips and also to sort of sand blast them as the cold mixture swirls around them which greatly expedites wear.Your much better off letting it sit than idling for it 30 minutes.

When I started driving semi's I was taught that when you idle a diesel engine the oil pressure is too low for an extended idle. Tearing engines apart after drivers idled to sleep, it was found that a lack of oil pressure did most of the idle damage. By bumping the RPMs up 200 or 300 it raises the oil pressure to better lubricate the engines component. The engine will also run closer to normal operating temperatures. The "high idle" function of the cruise control serves this function. Turn your cruise control on and bump the accelerate button. The RPMs will come up to 900-1000 RPM. Turn off the cruise control or press the brake peddle to drop RPMs before you turn off the engine.It is not needed to start and idle the engine every two weeks for 30 minutes. Unless you plan to drive it just let it sit. Put a battery charger on it if required but running it at idle will not get it up to temperature and can harder on the engine than letting it sit. Farm engines sit for months between use.

Do NOT start your engine every two weeks and just let it idle, even high idle.All you are doing is adding moisture to the crankcase.If you start it, drive it at least 25 highway miles-- enough to get the oil, not just coolant up to operating temperature. This advice is from both Caterpillar Corp and Cummins Corp. Has not changed-- has always been this way.And, yes, with 2007 and newer engines, idling clogs up the DPF (Diesel Particulate Filter). They are much more sensitive to long periods of idling than previous engines. Doesn't matter what engine brand.

A Diesel at Idling RPM’s ....... | Good Sam Community

32 Replies

hone_eagle
Explorer
Feb 02, 2014
My ECM can be read in the dash DID ,fully 1/3 of the engines( D12)life has been at idle,it has now more the 800,000 klms.
A recent dino shows power is still at over 90% of new.
hooligan
Explorer
Feb 02, 2014
More info here. PowerSpec

Cables now are expensive $$$$.
Mr_Mark1
Explorer
Feb 02, 2014
hooligan wrote:
It's all in the ECM...
I have Cummins PowerSpec. Reads engine parameters. ECM gives following info:
Engine faults-(codes)
Total (lifetime) ECM hours, fuel used, idle time, idle fuel used, engine hours.
Trip totals, trip time, distance, idle fuel and total fuel used, drive fuel and distance, number of coasts out of gear,total top gear time and distance, sudden decelerations, maximum engine and vehicle speed, service brake actuations, trip fuel used and fuel economy, engine running not moving time, and a few dozen others.

FWIW- The computer shows 7 sudden decelerations since new (2001) I remember all of them and a few more.:E

The next time I have our coach in for service, I would like to know all of those answers just for curiosity sake.

MM.
hooligan
Explorer
Feb 02, 2014
It's all in the ECM...
I have Cummins PowerSpec. Reads engine parameters. ECM gives following info:
Engine faults-(codes)
Total (lifetime) ECM hours, fuel used, idle time, idle fuel used, engine hours.
Trip totals, trip time, distance, idle fuel and total fuel used, drive fuel and distance, number of coasts out of gear,total top gear time and distance, sudden decelerations, maximum engine and vehicle speed, service brake actuations, trip fuel used and fuel economy, engine running not moving time, and a few dozen others.

FWIW- The computer shows 7 sudden decelerations since new (2001) I remember all of them and a few more.:E
RVUSA
Explorer
Feb 02, 2014
wallynm wrote:
I can not convince you as you need to go talk to the service manager of your local franchised Cat repair facility. I can tell you that they can read how much time you let it idle by reading the ECM. Ask me how I know.

I'll ask, how do you know that Wally?
RVUSA
Explorer
Feb 02, 2014
wny_pat wrote:
Here is what Cummins says about Extended Cold Weather Idling:
"Extended cold weather idling

That was a great read. Thanks for posting it.
Airstreamer67
Explorer
Feb 02, 2014
Some diesel engines have exhaust brakes. If the exhaust brake can be activated while idling, this could raise exhaust temperatures enough to help avoid idling problems related to low combustion temperatures.

At least one engine, the 7.3L International (Ford PowerStroke), has a factory exhaust restriction device that is automatically activated on cold start-ups. It was designed to warm up the engine faster. Some folks modify it for use as an exhaust brake too, as it works on the same operating principle.
Alan_Hepburn
Explorer
Feb 02, 2014
ScottG wrote:
Your engine will not get up to operating temps. This is very hard on the injectors for one. The colder temps inside the combustion chamber cause the fuel to cause build up on the tips and also to sort of sand blast them as the cold mixture swirls around them which greatly expedites wear.
Your much better off letting it sit than idling for it 30 minutes.

It's not so much that the injectors get build-up on them - the cool combustion chamber temperatures cause the fuel to not burn completely. It ends up condensing on the cylinder walls, and washing the thin film of oil off the walls. The fuel ends up getting past the rings and into the crankcase, thinning out the oil. So, you lose lubrication on the cylinder walls, causing wear from the rings, and thin out the oil, causing more wear on all the lubricated parts.

Look up "wet stacking" for a fun read...
down_home
Explorer II
Feb 02, 2014
We don't idle our at "idle" we bump it up with the cruise control if it doesn't itself. Only while we are disconnecting or when it is especially cold a little longer.
I had thought it was a new emissions caused problem when they upped the operating temp, lowered compression and increase fuel leading to wash down of cylinders at idle. I think it all started about 04 for diesels.
So I learned something new. :)
imgoin4it
Explorer
Feb 02, 2014
I had a Cat 330hp 3126. The Cat book that came with the coach explained it very well. Causes cylinder liner wash down because of inefficient fuel burning and would score the liners. Do you have the book that should have come with the engine?

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A Diesel at Idling RPM’s .......

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