idle time

[Bandit1]

i was wondering how long is safe to idle a 12v? also does it hurt the engine in anyway to turn it off for a few mins rather than let it idle? thanks

 

[Joe G.]

The key is EGT. If you let it idle very long with the EGT below 300 the fuel doesn't burn right and varnish forms. That can cause sticking valves and/or rings. It's better to turn it off after you let it cool to 300. If you have an exhaust brake leave it on to keep the EGT up if you want to idle for a while.

 

[Cooker]

I went though this same thing when I first got my truck.



You shouldn't let the truck idle for more than 10 minutes. With a high idle device some feel that you can let the truck idle forever as long as your EGT's stay above 300. TAnother way to keep you EGT's up is with an exhaust brake. The high idler won't keep your EGT's too warm, but an exhaust brake will. Cummins says not to idle the truck for an extended period of time even with a high idle, but they say (approve of) you can idle for extended periods with the exhaust brake partially closed.



As far as shutting it down for a few minutes vs. leaving it running. As long as your post turbo temps have cooled off to 300 degrees you can shut it down no problem, and if the truck is going to stay warm (summer) you might as well shut it down vs. leaving it running. In the winter I prefer to leave my truck running because it cools off too quickly when it's real cold outside. I plan in installing a high idle device to keep the truck rev'ed to 1200 RPM's. Even though Cummins doesn't really appove of this method, I personally would rather leave the truck running for 10-15 minutes than shut it off.



This seems to be a personal preference topic, so to each his own.



I hope this helps,

Ryan

 

[Dennis Garrett]

If you come in off the highway hot, & let it run 10 minutes or so while you fuel it & do the glass, that's OK, it will stay hot for a while. If you let idle on a cool morning thinking it will warm up while you finish the paper & eat breakfast, forget it, it will not warm up. In other words, you can idle a hot or throughly warmed up engine for a while, but don't idle an engine that's still cold, it will stay that way. If you have an auto & idle more than momentarily, set the brake, & idle it in "N", not Park.

 

[barkerdl]

Why choose Neutral rather than Park? Thanks.

 

[Cooker]

The transmission fluid does not circulate in park, but is does in neutral.



-Ryan

 

[Eric_77]

Originally posted by Cooker

The transmission fluid does not circulate in park, but is does in neutral.



-Ryan

Huh? I had always been told to put a vehicle in neutral to start it if battery is weak or very cold outside because transmission was "truely" in a no gear state.



Maybe I was told wrong.



Anyway I have let my truck idle overnight while I was sleeping to keep A/C running and other than a hesitation when first starting out and bit of black/gray smoke all was good. Later I found out about extended idling was bad but still do it on occassion and don't burn any oil (5k oil changes). Maybe the a/c compressor was keeping enough load that things don't get too bad and outside temp was always 85+ degrees but with the rough running I bet I wasn't doing engine any favors.