High Idle w/ Engine Fan on for 10 hours..????

Back when I ran a mechanical truck it would idle at 900-1000 with the fan on all night long. But those are just a knob on the dash that screws in and out. I idle all the time now but it's only during the day haven't spent the night in a truck in a few weeks.

 

One can get by idling 800-850. There is no need idling higher than that. Anything higher is considered excess idling.

The fan relay and AC relay are tied together along with the fan switch and ECM. So the AC on an additional load on the engine makes a difference. But why idle unless you have the AC on?

There's a heatwave going on too so that plays a part with the cooling system temp.

I assume you are idling as fast as the cruise will allow? No that is not necessary and considered a nuisance by your neighbors.

If your boss wants to do the right thing then invest in a tripac. They pay for themselves in 12-13 months and nothing but increased profits and less wear and tear on the engine.

 

the fan comes on to reduce high pressure in the condensor.

keeping the fan on.cools the water down. and cools the oil down. cooler oil provides higher pressure then hotter oil. and provides better a/c.

higher idle increases oil pressure. and keeps lubrication going in the transmission. the shaft bearings have a habit of making noise from low idle. lack of lubrication. supposedly there's a pump in the transmission. the engine crankshaft also spins faster. creating a better oil splash up into the lower cylinder walls.

higher idle provided better fuel consumption. as the engine isn't struggling so much to idle. back in the carburated days. when backyard mechanics LOVED to lower the idle on the V8's. the engine would run rough. to compensate. you'd richen the air/fuel mixture screws. to smooth out the lower idle. thus, burning more fuel. you would also fail emissions. and couldn't license your vehicle.

higher idle provides better fuel burn. cleaner emissions.

back to the fan. be nice if ALL manufactures had switches in the dash. (((( FREIGHTLINER ))))

i spent the night once. where some idiot idled at 1500 all night. with his fan on. he was the only truck running. temps were perfect for sleeping. if the windows could have been left down. but who wants to hear that idiot all night.

 

Its for the emmisions to high idle. Certain components get sooty with carbon at low idle. Depends on year if that would be reason to high idle.

 

The other day it was hot, someone was idling probably in excess of 1,300 RPM I suspect, and the fan was cycling on/off. You could hear that truck literally from the other side of the [large] truck stop. There was no reason to idle that fast.

 

Dd13 operators book specified sulfuric acid build up, aside from emissions control. Cummins isx 15 made a mention about it as well.

 

You just have to drive something besides a fleet truck, snowwy!


I've seen fan overrides in every brand of truck. It's all about the spec.

 

I installed a manuel switch in mine. I turn it on prior to climbing the hills. Helps keep the temp down faster in a hard pull.
Mine is idling now here in Baytown as it's hot and I have the a/c going..900 rpm.
Yes the fan can and will stay on like others have posted due to the a/c running and the outside temp and humidty.

 

Condenser pressure equates to temperature of the condenser.

I don't get this, if your coolant temps are high just sitting, then you have a cooling problem and need to have it checked. Idling or no load high idle no matter what engine should not produce the temps that are needed to have a fan kick in to cool it down.

 

Actually, if you're faced downwind, it's quite easy to have an engine warm up enough to kick the fan in. The hot under-hood air flowing forward through the radiator dramatically reduces the cooling efficiency due to the much lower fin to air temperature difference.