How much is too much idling

[chuckd]

I have a fast idle on my Shorty Prevost with a 6V92, and use it when I am idling.  See lot of warnings here about not idling, and sometimes I have no choice.  Low air pressure being the primary reason, but also when changing the leveling valves etc.  So my question, for how long a time can I idle my two stroke?

TIA Chuckd

[Eagle Andy]

Hey Chuck when I bought my 68 with a 92 the PO told me no more than 5 min Now I wonder how when they used these thing for over the road trucking back in the day . How did the truckers get away with it ? Iam sure they Idlled a lot . Iam just wondering myself

[robertglines1]

In the real world my first MCI was a transfer coach from a airport to down town..it spent hours a day sitting still awaiting passangers but after idle time it was run up to speed for about the 45 minute Tripp to it's destination then sit again..I ran bus 5 yrs after getting with no engine problems. Do you think truckers shut engine off at truck stops or rest stops in cold weather and get cold..I know some have other heat sources now.But remember our 2 strokes came from days of cheap fuel..so not good for---but in real life you are doing less than was practice in commercial use..back (cheap fuel)it cost less than $2 a hr idle time  now $15 plus..Note I did say not good for....but       Bob

[lostagain]

If you have to idle, use fast idle. You need to spin the alternator fast enough to charge. You need to circulate the coolant and the oil.

Even at fast idle, it will run well below operating temperature: not really good.

When I drove in the '70s, if we were overnight in a hotel at 30 below, we would just park at the back of the lot and leave it idling all night. Off course these old buses had functioning rad shutters, which helped with the temp.

The MCI D I drive for the hockey team has a Webasto, greatest invention since buses were discovered...

A few years ago when we had the Greyhound agency in Invermere at our gas station, a memo came one day from the VP of fleet maintenance in Dallas about idling: it said avoid it as much as possible to cut down fuel and maintenance costs, noise and pollution. And if absolutely necessary, use fast idle.

I shut mine down as soon as I can.

JC

[trucktramp]

I put many miles on an old Jimmy Astro with a Silver 8v92 and I idled it alot.  My mechanic said that it should be brought up off idle to around 1000 rpm because that brought the oil pressure up from around 5 lbs. to about 30.  Back in the day there was a theory that at idle the oil pressure was so low that the back 2 cylinders wouldn't get enough oil for lubrication.  I can't recall anyone having problems of that nature though.  Clifford could probably confirm this if it is so.  My mechanic also said that fast idle kept the lubricant from being washed off the cylinder walls.  I do recall that it made the truck shake less when sleeping.

[bevans6]

The manual says if you have to idle, keep it over 800 rpm.  It says that the engine coolant temperature will fall below normal operating range, leading to incomplete combusion of fuel leading to dilution of crankcase oil, formation of lacquer, gummy deposits  on valves and rings, and sludge...  and to keep it over 800 rpm.

brian

[TomC]

Thee hardest thing you can do to ANY Diesel is to let it idle-why?  Because at idle it produces the most amount of vibration (less on a 2 stroke) and all that vibration is being transmitted through the rod and main bearings.  When I was driving my 8V-92TA, my mechanic put a shim in that allowed me to pull my hand throttle and the governor would bump up against 900 rpm for long idle times (like on a very cold winter night).  On my truck with the Caterpillar, as soon as the oil pressure goes over 65psi (in about 20 seconds), I have a ball point pen that is just the right length that I jam between the gas pedal and the dash to produce a 1,000rpm fast idle (Caterpillars have full rpm governors that hold the rpm with the pedal).  1.2 million miles on the engine (with 2 in frames, but never out of the truck [even the mechanics said the old jacket water aftercooled engines didn't go much more then 500k miles between overhauls-that's another reason they came out with air to air intercooling]) says I must be doing something right.  Good Luck, TomC

[CrabbyMilton]

You can always just say that you are not idling. You are simply using the bus engine to power ac and generator.

[Lin]

Not being a true expert, I do not know for sure what effects idling can have.  I do know that it spits more oil, which is something I like to avoid.  No matter how much idling does or doesn't have negative effects, I also know that not idling has less.  My practice has become to avoid idling at all.  Obviously, you will be idling at lights and in some types of traffic, but other than that, if I stop I shut her down.  I try to air up with the electric compressor, so when it's time to move, I just put it in gear and go.  If I am going to air up using the engine, I do it at over 1000 rpm.  I have to sit there to do it since Don ruined my fast idle switch with his fangled Jakes.

[4905 doc]

In the 70's and 80's,in VT, whenever the temps were heading to somewhere near 20-30 below, we left the entire fleet of trucks idling all night. rolled bearings in them every 500,000 miles. most bearings looked as good as the new ones. granted, fuel was cheaper, but still, the fact remains, idling didn't seem to affect the lifespan at all. this included 2 stroke detroits, and 4 stroke cat and IH.
lets remember, that sometimes, the facts get lost in the fog of PC.

[chuckd]

Thanks guys, appreciate all the feedback.  Take away is idle on fast idle, and if you get into a situation where you have to idle, do it guilt free.  At least from the engine standpoint.

Chuck - who is using the Texas technique for snow removal - let the sun melt it.

[Len Silva]

I think that like most commercial operators, if you are going to get up and run after a long idle, it probably wont hurt anything. If, after a long idle period, you are going to shut it down, that would not be a good thing.