How Long can I idle

[budbud7]

I have a1999 Cummins 5.9 Thomas bus. I want to camp out in it one night and run the on board a/c. Will it hurt to run the engine all night? it has a high idle switch also.

[Brad_SwiftFur]

I drive big trucks for a living and generally leave mine idle all the time. Of course I'm not running the 5.9 engine either. I remember reading something about using the high idle to avoid excessive low combustion chamber temps (I forget the details of it now), it's particularly relevant in winter temps. On a regular basis it will increase wear and tear on the engine and such, but for one night every so often it should be fine.

You'll want audible warnings and shut-downs enabled. You won't want a ruined engine if you snap a belt in the wee hours and the engine overheats, you'll want it to shut down instead.

[cowlitzcoach]

Idling a bus, even on fast idle to run the A/C system, is not a very good idea.

It will tend to not get the engine warm enough which will tend to create a lot of moisture that will condense inside the crankcase and exhaust system which will cause premature wear and failure.

Also, with the engine running fast with virtually no load the engine will not be running very efficiently. It will tend to not burn all of the fuel that is entering the combustion chamber. That excess fuel will tend to leak past the rings into the crankcase where it will dilute the oil. With the oil diluted it will tend to cause more wear in areas like cylinders, bearings, rockers, etc. The no load will also tend to make the exhaust dirtier and it will tend to gunk up the valves, the top of the piston, the top ring, and the exhaust system.

If you need A/C either plug in or get a genset to run a window shaker or roof top RV A/C.

[JDOnTheGo]

Howdy Bud, my 1998 Detroit Diesel 60 manual says the following, not certain this is applicable to your motor but I suspect it is:

"Avoid Unnecessary Engine Idling. During long engine idling periods, the engine coolant temperature will fall below the normal operating range. The incomplete combustion of fuel in a cold engine will cause crankcase dilution, formation of lacquer or gummy deposits on the valves, pistons and rings and rapid accumulation of sludge in the engine. NOTE: When prolonged engine idling is necessary, maintain at least 850 r/min spring/summer and 1200 rpm fall/winter."

[bigskypc50]

Buy a $300 dollar generator and $100 dollar window AC and idle that all night and not your $5000 plus engine and drivetrain. I agree with others not good for the engine at all or fuel you will 0 MPG

[mmoore6856]

the high idle switch was put in at the factory for extended idle periods. if you cant maintain engine temp at high idle then you have thermostat issues that need to be addressed. one nite a week is not a problem

[jazty]

Originally Posted by mmoore6856

the high idle switch was put in at the factory for extended idle periods. if you cant maintain engine temp at high idle then you have thermostat issues that need to be addressed. one nite a week is not a problem

I don't know for certain, but in my opinion the high idle switch was put in place for winter idling, usually to warm things up a bit, or for short idling situations. Most engine manufacturers consider long idle times as "Severe Engine Service". If you're going to be doing it on any regular basis you need to follow the severe engine service maintenance schedule, which is expensive.

[mmoore6856]

It was put in for summer ac use also for us truckers sleeping on a asphalt parking lot in the day if you are on a nite drive schedule

[Brad_SwiftFur]

I will agree with comments made by others regarding lowered coolant temperatures. It should remain at operating temperature the whole time, if it doesn't, it should be checked (mine does). I will also agree about the various incomplete combustion and oil dilution comments. It often does put an engine into "Severe Service" rating which, for the most part, includes much more frequent oil changes which addresses the oil dilution concern.

With all that said, I would (and do) leave it idle and let the A/C run. Keep a check on the oil, change more often as needed, and the most important thing is to leave auto-shutdowns enabled. You don't want to wake up to an overheated and blown engine because of a snapped fan belt.

[BowserJournal]

This is one of the reasons we are moving from our stock roof mounted AC units to RV style. SO we don't have to idle to be cool.

[Iceni John]

It makes no sense to run a 200 HP engine to power one little A/C. Just because you can crack a nut with a sledgehammer doesn't mean it's a smart way to do it. Buy a small generator like a Honda or Champion and use that instead. Mind you, if it's so hot that you need an A/C running all night long, maybe it's not the best time of the year to be tin-tenting at all!

John

[joeblack5]

I agree with what has been said but I would nor worry about idling it after it ha gotten on operation temperature. Most of the professional truckers ignore these realities and let their 400+ HP engines happily idle all night long to get a little heat or cool out of them. For the recreational users like us that probably do not put more then 150.000 additional miles on our engines the extra wear and tear would hardly put our engines over the edge.

later J

[CaptSquid]

The ONLY time I idled my Freightshaker was on Long Island. The temp dropped to 1º that night and I didn't want to freeze portions of my anatomy. Later, I bought an electric mattress pad, which I still have.

[BlackJohn]

I use my high idle to act as cruise control when rolling.
Mostly on at warm up once the engine fire up so I can go out to remove snow on the hood etc. last couple of nights here were chilly at or below 0C. And it is only September. Haven't resorted to lighting the woodstove up yet.

John

[cadillackid]

Originally Posted by BowserJournal

This is one of the reasons we are moving from our stock roof mounted AC units to RV style. SO we don't have to idle to be cool.

that will work for being parked but you'll roast when driving... esp into the sun in the south... I suggest you keep both.. that will give you best of both worlds..
-Christopher

[cadillackid]

on my last trip home I got sleepy durimng the day so i left my bus running wioth the A/C on to take a couple hour nap.. heck it was going up to 205 just sitting and turning on the Coolant fan.. then dopwn to 195 and off..

in winter my red bus has a built-in computer program that automatically idles the emgine up and down to maintain a preset coolant temp.. I think I have it set at 175..

-Christopher

[budbud7]

Well I'm still not sure what I should do. I know very little about diesel engines and I don't want to mess mine up letting it idle all night. When I have used the high idle switch, it don't seem to be cold because the electric fan kicks in every now and then. I don't have a generator but i do have a small window a/c unit. Not sure if it will fit in my window with some modification. Is it anyone on here with a 5.9 24 valve that want to make a comment?

[cadillackid]

some added thoughts...

is this a permanent thing or a one night thing? ie is this how you plan to camp all the time? or just this one trip? if its just one noght and its hot enough to need A/C, your engine isnt going to cool down unless the thermostat is bad and the fan is blasting away... in fact simply perform a test.. go drive your bus for an hour... then on an evening with similar weather you expect to be in when camped let your bus idle for an hour. with its A/C on.. fill it to the brim close to home before you start, and see after an hour does the temp gauge stay up or drop some.. if the cooling system is over-zealous it usually cools down quickly.. then go drive it right back to the fuel station and top off the tank to the brim.. gets you an idea how much fuel you'll burn also..

a genny and a portable 2 hose A/C unit will cool your bus at night.. during the day forget it.. but thats also an option and doesnt require any mods... you'll need a good powerful generator to start the compressor...

-Christopher

[mmoore6856]

Go talk to your local dealer ask a mechanic as here are lots of opionions and few facts. Not many here are certified mechanics however the drivers have lots of firsthand experience at this but its hard to sort them out sometimes i feel like i should be wearing rubber boots here

[budbud7]

No this is not what I plan to do on a regular bases. I have to go to East Texas to work on a house with no electricity. Not ready to buy a generator large enough to run a small a/c. I might have to find a hotel but I will play it by ear.