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johnhicks · 12-03-2020, 11:31 AM

Let's assume that the MH can't be driven, and it has a mechanical 6BT Cummins. Of course this engine is subject to "old-timey" engine rules and problems.

It's widely said that an idling diesel will never reach "operating temperature" that would drive moisture out of the oil. Can it be reached by fast idle at around 1500rpm or even higher? If so, is there any reason to not do that occasionally?

HarryStone · 12-03-2020, 11:49 AM

It needs a load, and you can't generate a load by idling, even a fast idle.

twinboat · 12-03-2020, 12:07 PM

Heating and letting it cool will create more moisture the just letting it sit, why not leave it off between uses ?

wolfe10 · 12-03-2020, 12:18 PM

Both answers are correct.

If you can't drive at least 25 highway miles, don't start the engine.

Equally important while storing is to have a BIOCIDE such as Biobar JF in the fuel tank and tank full to minimize condensation.

Talloaks · 12-03-2020, 12:51 PM

Quote:

Originally Posted by johnhicks

Let's assume that the MH can't be driven, and it has a mechanical 6BT Cummins. Of course this engine is subject to "old-timey" engine rules and problems.

It's widely said that an idling diesel will never reach "operating temperature" that would drive moisture out of the oil. Can it be reached by fast idle at around 1500rpm or even higher? If so, is there any reason to not do that occasionally?

Often, what is "widely said" is not as useful as what the manufacturer of the engine says.

Here is a link you can use to find the operating manual for your engine. You will need to enter the ESN. https://www.cummins.com/support/manuals

My CAT C9 engine operating manual warns against excessive idling. It states that if excessive idle time is required, increase and maintain engine RPM above 1000, and ensure engine coolant temperature exceeds 180 degrees F.

Ray,IN · 12-03-2020, 08:06 PM

So there you have it JohnHicks; 5 replies and we all agree extended idling is bad for a diesel engine.(Cummins defines extended idling as >10 minutes)

Talloaks · 12-03-2020, 08:39 PM

OBTW, OP Hicks, thanks for prompting me to learn something new today. I had never heard of the "Gnat Line" until reading it on your post.

But wouldn't it be better to be wandering "above" the gnat line? Just trying to understand.

johnhicks · 12-03-2020, 08:54 PM

Talloaks, it appears that Cat suggests that fast idle and 180F temp is ok for extended idling. Do you read it the same way? My operating manual just says to avoid excessive idling but the engine doesn't have any way to set fast idle other than hold the pedal down.

Yes, it's lots better to be above the gnat line but I always find myself below it for some reason or other.

johnhicks · 12-04-2020, 11:23 AM

I did a lot more research and concluded that if idling more than about five minutes fast idle is greatly preferable if not virtually required. I knew that, but what I wanted to dig into was getting moisture out of the oil, and that fast idle will get the temperature up enough to do that plus prevent wet stacking.

Also of note is that low idle causes lots of problems with exhaust systems in modern engines.

So no, I still won't be cranking it up to "exercise" the engine, but if I do need to let it idle more that a few minutes I'll be more careful to keep rpm up.

Thanks to all.

Talloaks · 12-04-2020, 02:19 PM

Quote:

Originally Posted by johnhicks

Talloaks, it appears that Cat suggests that fast idle and 180F temp is ok for extended idling. Do you read it the same way? My operating manual just says to avoid excessive idling but the engine doesn't have any way to set fast idle other than hold the pedal down.

"Avoid excess idling. If the vehicle is parked for more than 5 minutes, stop the engine... Excessive idling can cause carbon buildup and/or excessive idling can cause the engine to slobber. This is harmful to the engine.

If extended idle time is required, control the engine rpm to 1000 rpm or above 1000 rpm. Ensure that the coolant temperature exceeds 82C (180 F). Consult your Caterpillar dealer for assistance."

This is from the Cat Engine Operations manual. It is discouraging idling your engine especially beyond 5 minutes. But...if for some reason you feel you have to... at least run the rpms up and get the coolant temperature up. And, my own editorial comment here, recognize that you are not doing your engine any good in the process.

Bobby F · 12-04-2020, 02:46 PM

We used to keep magnetic block heaters stuck on the oil pans of old Thiokol snowcats during the offseason storage to drive the moisture out of the oil. That was Thiokol's recommendation. They certainly wouldn't reach operating temps, but we'd leave them on for days at a time, and the heat would eventually vaporize the moisture out. Kept the internal rust away during the summers.

ArtJoyce · 12-04-2020, 03:08 PM

Quote:

Originally Posted by Talloaks

Often, what is "widely said" is not as useful as what the manufacturer of the engine says.

Here is a link you can use to find the operating manual for your engine. You will need to enter the ESN. https://www.cummins.com/support/manuals

My CAT C9 engine operating manual warns against excessive idling. It states that if excessive idle time is required, increase and maintain engine RPM above 1000, and ensure engine coolant temperature exceeds 180 degrees F.

My cummings also warns about idling. My cummings when parked, if I trun on the cruse controller and hit the set button. It will increase the idling to 1,000 RPM.

Which what I do when getting ready to head out to build up air and warm it up a little for about 10 minutes. Also before shutting down to cool down the top end for a few minutes.

johnhicks · 12-04-2020, 07:05 PM

I do agree that no idling at all is best.

Intersting note about block heaters. I do have a block/oil heater.

Ray,IN · 12-04-2020, 07:07 PM

Quote:

Originally Posted by ArtJoyce

My cummings also warns about idling. My cummings when parked, if I trun on the cruse controller and hit the set button. It will increase the idling to 1,000 RPM.

Which what I do when getting ready to head out to build up air and warm it up a little for about 10 minutes. Also before shutting down to cool down the top end for a few minutes.

A side note; your Cumins manual also says there is no need to cool down their engines unless you have been running hard. The time between exiting an interstate and arriving at the CG is adequate cool down time. Same for warm-up, by the time you reach the interstate the engine is warm enough to run without full-throttle.