Extended Idle How Long Is Too Long????

[jgillott]

This is my first post so please excuse me if it is a stupid question. I have a 2001 24 valve 4x4 that I bought new. I basically use it around the place pulling trailers and equipment. I spend some time, 15-20 min, at idle dropping one load and hooking another. I have read several posts that talk about damage from excessive idle. Am I killing my engine???? Should I rig some type of idle control? I'm only at 10k now so I'm hoping that I have not done any damage.

 

[Fireman Dave]

Welcome to the TDR jgillott - there are no stupid questions.



5 minutes is considered about the limit for idling. After that, it's not good. As you may know, you do want to let it idle to cool the turbo before shut down. Some guys have auto shutdown devices - shuts the engine down when the turbo gets to 300 degrees. A pyrometer helps tell you when it's safe to shut down. If you keep the rpms up, longer idle is ok. An exhaust brake - if you have a stick - can also enable you to idle for long periods of time without a problem. There are others on here that will probably be able to give you good info on this question too.



Good luck.

 

[jgillott]

Thanks

To tell you the truth, I have never really considered how long I let the thing run. I've dealt with many big trucks, but they have always had some type of idle control. I'll have to look into something in the near future.

 

[Mingoglia]

I had my '01 idle for almost 2 hours about 2 months ago. I lost the second trailer tire in a single trip and my wife and niece were in the truck while I left to try to borrow a tire to get home. Keep in mind it was over 100 degrees outside (I live in Phoenix) so I don't think the truck was having any problems keeping the heat up. I don't think extended idle is too bad as long as the engine remains in the operating temperature range. Anyone disagree?

 

[Fireman Dave]

Agreed, Ming. J - the problem with a diesel idling is it runs so cool. If a load is kept on it with an e-brake or high idle, it's fine. At least that's my understanding of it.

 

[jgillott]

Unless I actually drive it somewhere, I don't think it ever reaches full operating temp. It seems that if it is just ideling, it never fully warms up. Especially in the winter.

 

[Got Smoke?]

Originally posted by Fireman Dave

If a load is kept on it with an e-brake or high idle, it's fine. At least that's my understanding of it.

correct me if I am wrong but you can't rig up a high idle without factory cruise control can you?

 

[MCummings]

Idling can't be TOO bad for the motor,, in my field of work, sometimes my truck has to idle for several hours on end.



With the outside air temp between 90-110* my water temperature doesn't fall below the lower safe range, and EGT doesn't go below 275* (with A/C on)



My truck has run 39 hours straight, and idled for 36 of them. I traveled 233 miles and used two tanks of fuel.



These motors are TOUGH,, as long as you run 'em hard occasionally, they will last a LONG while.



Change the Fuel filter, keep good Fuel Pressure,, Change the oil and filter every 3-5K (Depending on driving and BOMBs) Don't romp on it too hard when cold.



My $. 02



Merrick Cummings Jr

 

[BushWakr - RIP]

Someone will correct me if I'm wrong but part of the problem with extended idle is that since the engine tends to run very cool at idle you can start to have cylinder washdown. That's raw or unburnt fuel on cylinder walls. This is not a good situation. Also, you can increase oil contamination rate/levels as well.

You carbon up the cylinder/nozzles, and perhaps, exhaust valves as well.

If you have made any significant mods to fueling you will find that some or all of these items become even more pronounced since your pushing more fuel in than stock conditions do. If your idle is even a tad low, you'll have reduced oil pressure as well.



I may be off base here, but I think that idling for several minutes with an engine that has been run up to normal temps will not cause any lasting damage or harm to components.

If you cold start an engine, walk away, and let it sit idling for extended periods, then you may well have problems with that type of situation.



Just my thoughts on this...



Bob.

 

[MCummings]

BTW, I drove 110 Miles to the "Location" and didn't shut the truck off until I got back home (110 miles back to the house)



I feel that idling a motor with water temp below 140* is bad (For extended periods)



Heavily BOMBed trucks do require alot more maintanence.



Idling Heavily Bombed trucks isn't good because of large injectors, and lots of air flow will keep combustion temps Low with lots of un-burnt fuel.



Hey,, but do what ya want. ,, I'm bombed heavily, but still idle alot,, but I do have a sponsor for my oil



Merrick Cummings Jr

 

[Shovelhead]

My understanding is that the "Extended Idle" problem was related more to "Warm-Up" idling on cold mornings.

If the truck is at operating temps, whats the diff between idling while parked and sitting in bumper-to-bumper traffic?

 

[illflem]

My experence with extended idle and washdown

Have a JD tractor that is used only for spraying, the engine would idle for up to half an hour while refilling, engine totally warmed up. Never could figure out why the oil level kept on increasing till I realized it was diesel from washdown getting in the oil. Now run the engine at high idle while refilling, no problem. I vote for 5 minutes max warmed up or not unless you jack the idle up.

 

[Pit Bull]

I can see where there would be times when you would need to idle longer than 5 min's (like, flat tire and family in truck with 100 degree weather) but these would be rare. I guess I am wondering why you would want to idle more than 5 minutes? Just as easy to start it and stop it. I let mine idle when I fill up with fuel (around 5 minutes) because it is easier than sitting and waiting for the engine to cool down before shut down.

 

[WadePatton]

EPA

I believe that (until proven wrong) Cummins has to go along with every little whimsicle notion promoted by the EPA. Hence we have prohibitions on fuel/oil additives and extended idle--and of course BOMBing!



If my cylinders are washing down, then I should be able to detect fuel in oil and there would be smoke at the tailpipe, no? I will continue to leave mine run for the dog's sake 10-15 minutes at a time.



I don't buy it.

 

[Steve St.Laurent]

I've read articles from performance vendors as well stating that extended idling is bad news for diesels - including big rigs. The problem has nothing to do with coolant temp but has everything to do with combustion temp. What happens is if your combustion temperatures are too low (<300 degrees is the number I've heard) then you will get incomplete combustion of the fuel in the cylinder and get cylinder washdown like said above. Caterpiller has installed exhaust brakes on some engines right from the factory and uses them for warm up for this reason. The recommendation I've seen (from performance vendors as well as oem's - so it isn't an EPA thing) is to let the oil pressure come up and then drive conservatively until the engine is warmed up instead of trying to idle to warm up unless you have an exhaust brake. I use my exhaust brake for warmup and for extended idling and my EGT's will sit at 550 degrees or so which is plenty to burn all of the fuel in the cylinders. A friend of mine idled his 12 valve for a couple of hours once with the A/C on waiting in line at the dunes once. When he pulled out it belched out HUGE clouds of white smoke - scared the . . . . . out of us - we thought he'd blown it up, didn't know anything about diesels at the time. JMHO

 

[CUMAPART]

I agree with Steve. Idling isn't good for our trucks and that goes for big rigs as well. You hit the nail on the head about incomplete combustion. I let mine idle for three minutes in the morning then I'm off keeping the RPM's below 1800 until she's warmed up. I'd much rather warm it up by driving it conservatively than by sitting there letting her idle.

 

[Mingoglia]

I think the idling to warm up is a completely different animal than driving for hours and then sitting in a truck stop for an hour or two with your exhaust brake and idle control on to catch some ZZZZ's during a cold winter (like the Hotshot's do). Yeah, it's not good for it, but is it really 'that' bad as long as you can keep some load on the engine?

 

[BCaldwell]

Idling

m2c worth, I have driven big rigs for too many years[old mossy back] I was taught[not in a drivin' school] to get oil pressure and then bring rpm's up to 1000 high idle and let engine come up to operating temp. This method has served me well with detroits cats macks binders and cummins engines, and pyro down to 300 to shut down 3-5 minutes. bill

 

[FAllen]

BCaldwell



Thanks for sharing your ops tips but as a new and untrained diesel operator what is the proper operating temperature that was suggested in your training?



TIA



Fred

 

[BCaldwell]

FAllen, as far as temps go on our dodges the suggested spot to mount the thermocouple for the pyrometer is in the exhaust manifold just before the turbo mounting flange, on the first gens 1250 is about as high as you want to take it for a very short period 1150 1200 should not hurt anything but you should have even lower temperatures than these during normal unloaded operation. bill