I'm probably going to purchase a '91 Chevy Top kick Bucket truck with a Caterpillar 3116 engine that has 71K mi. I'm a little worried about the extended idel periods these PTO driven hydrulic bucket trucks see, you know ...drive to the job,set up the boom, idel for hours while running the boom. Maybe it's got a high speed idel control to keep the EGT's hotter while the pump is running. I would expect to see around 5000-6000 hours on the motor,of course most of them ideling. Don't we see alot of semi trucks ideling at the truck stops over night with out harm to thier engines? I'll try to get an oil analysis from the dealer but what else should I look for? Some are saying idel all you want with a deisel others say stay away from even low hour "ideled" engines.What gives?

 

Have you had any experience with these Cat 3116 engines in respect to long idle period failures? I already found out they are s-l-o-w-w-w-w-w as slugs.

 

Folks make way too big of a deal about extended idling. It definitely is a bad idea to try warming up a cold engine by idling it but once it's warmed up from driving it will cause little problem. The boom truck probably had it's pto engaged the whole time it was idling creating a load that kept the engine temps up anyway.
I wouldn't worry about it.
Sure fire way to tell if an engine has suffered from extended cold idling is to sniff the dip stick, if it has been over idled it will smell strongly of diesel even right after an oil change.

 

I work on boom (bucket trucks) every day.....when the boom is engaged the engines idle up to provide more power for the pump to operate the boom......at 750 RPM's the engine doesn't provide enuff power for the pump to operate the boom correctly........all this is built into the boom by the manufacturer

 

Extended idling IS detrimental to a diesel engine. What happens is that you get diesel fuel washing down the cylinder walls from incomplete combustion. The easiest way to avoid this is to simply install a high idle. The "big rig" manufacturers are realizing this extended idling thing. Back in 1997-98, we bought 8 new Mack dumptrucks. These trucks not only would only idle for 5 minutes and shut off, but they would not shutoff immediately. This addressed two problems (1- extended idling, 2- pulling in and shutting down hot).

I dont think that extended idling is gonna shorten the life too drastically, but it is an issue.

 

Like Pappyman said most units need at least 1200+ rpm to operate hydraulic accessories to maintain adequate pressures to operate properly. Second factor would be outside temperatures combined with coolant temperatures operating this way, like Pappyman said check for diesel in oil and tar like black streaks running down the stack. This is called slobbering where unburned diesel has been pumped out the stack and burned onto the stack. The little CAT is Sloooow- you don't qualify this statement, most of these little engines were in trucks at least double the weight of a pickup at the same or less HP ratings in a P/U. Secondly CAT diesels generally react and accelerate slower than a cummins of comparable HP ratings however CAT diesels are known for excellent holding power loaded heavier than other brands of diesels due to higher torque ratings. Engine configuration has a lot to do with it, Cummins B series are exceptionally peppy engines but don't expect this type of acceleration from an N14. Up here we haul super B's grossing 140,000lbs and CAT is the engine of choice because it maintains it speed on grades with this weight better than other brands in the same class. Also don't forget that bucket truck was driven to and from the work area creating heat which unless operating continously in extreme cold (-25-45F) would likely burn the excess off and clear the cylinders of residue. Diesel P/U's are no different people that idle around town vs those that drag 12000lbs regularily will see more carbon deposits and sluggish performance. Diesels including Cummins B's working steady at consistant higher coolant temps,EGT's and manifold pressures will be cleaner internally than those idled around town or short highway trips empty. Will they last longer, too many variables here to say definitely which ones survive longer. The topic of extended idling has waged war on these forums but due to our climate up here a lot of diesels including CTD's idle here to keep warm in the cooler/cold months and our engines get as many miles as the southern ones not idling. The method of idling has a bearing on the cleanliness of the engine, I personally don't follow Dodges recommendations and always run a winter front, high idle at 1400+ temperature adjusted to maintain coolant temp (175+) and don't drive my truck cold (140F and below). Take the 6000hrs it has x 50 mph= a basic equivalent of 300,000 miles highway, now how does it look for purchase. Hope this gives you some info to help understand the variables in a used diesel. PK

 

I may be wrong on this but we have a jet truck (Sewer Cleaner ) that runs the pump off of a PTO. When It is engaged the odometer still racks up miles on it I THINK . I know that it still registers MPH. It does put it under a load which is not much different from driving down the street. I would not worry about the Idle time on a truck like that.

 

I agree, the truck will have to "idle" faster for the pto. Most are set to atleast 1400 rpm, but the 300,000 miles, wait a minute, even of it was equal to 300,000 miles, would they not be considered "hi-way" miles, as there is no stop and go, so how much would that take off the mileage #'s. We've fixed some blowers on the Poo Poo trucks and they use a pto for the blower, you can't idle a diesel and get the correct rpms for the blower without some un-godly sized pulleys. Anyways, the engine speed is controlled to maintain a constant speed for the pump or blower $.02 worth

 

The 50mph is an average used to relate hours to miles and yes with different applications city to highway miles will vary. That said you are right but then a truck driven at - 40F and no water temp showing on the guage will also have higher wear than one at proper temps. A truck driven at extreme high temps will also show higher signs of wear so when converting we talk about an average that covers most applications when insufficient owner records are unavailable. One can start to interject all kinds of variables but unless the exact maintenance logs and driver logs are available it becomes speculation. An eg; would be a tandem gravel truck with an automatic trans city owned versus the same vehicle privately owned with a manual trans both trucks may or may not have same hours or miles but wear problems will appear in different components at different times. So when buying and trading used equipment the 50 mph rule is used as an average OK. Only scientific engine or component oil testing will give a more accurate indication of usage and life expectancy. VPI your pto should not register miles as this illegal to show inaccurate milages in vehicles being sold, only the hour meter should register if the vehicle is not moving. The pto runs off the side or top of the transmission the speedometer is supposed to register off of the trans output, driveshaft or drive wheel. PK

 

We just got a new Sterling boom truck for moving concrete forms. It has a C 12 Cat in it and the factory rep/trainer they sent out very strongly recommended against long idle periods, especially since the computer logs idle time. If any problems they will look at idle time. It does have a high idle for the PTO, kinda nice uses the cruise control buttons.

 

I have never heard or seen so many people worried about idleing times. I never worried about it, with a semi, bucket truck (yes I have been in a many of them),Bobcat,loader,tractor,or my DODGE. It is a diesel and that is how I treat it. MY truck has sat and idled for hours, so has anything else I ran. The bucket truck should never be off, last thing i want to worry about is being in the air and not getting down. When we worked in the cold months, the trucks were started in the mourning, and none of them were turned off till we punched out, didn't hurt'm.

 

OK folks, lets not get out of hand here trying to answer an innocent question.
The real answer is to check with the manufacturer, which ever engine you have, and see what they say about idling the engine. You will get as many answers that say not to idle as you will that say it is ok on here. It is like the oil debate wars, they never end.
It is your vehicle or your responsibility if it is a company vehicle so check with the maunfacturer and go from there.

Just FYI, I've had three of these trucks and I do not let them idle to warm up and I very seldom let the engine idle more than five minutes. To me, idling equals wasted fuel.

Thanks
Joel

 

This is not a fact for all trucks.
We have many trucks in our dept. [ Fire Dept. ]
And most spin the speedo and run miles up on the odometer while in pump gear.
While pumping on a fire scene or wreck, training whatever they will avarage about 45 mph.
They also have an hourmeter.
These are all factory design.
And in our dept. now the years of these trucks range from 1981~2003.



: Eddie :

 

Same with the fire trucks when I was in the fire service. They all racked mileage when in pump gear.

 

Fire trucks in pump gear will register mileage and speed because those pumps are enganged through a drop box and not a PTO. The drop box disconnects the d/s from the box to the rear wheels and connects the d/s to the pump while in pump gear. The front part of the d/s is still spinning, therefore registering speed. Very common on misdship pump designs.

Trucks that drive the pump off the PTO of course act like any other PTO driven unit.

We have both types in our dept.

Brian