Idle for 12 hours - JeepForum.com
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post #1 of 12 Old 07-12-2018, 08:47 AM Thread Starter
Anthony Bruno
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Idle for 12 hours

HYPOTHETICALLY, if someone left their 2018 Jeep GC limited idling for 12 hours straight by mistake, what damage would that cause?
...asking for a friend
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post #2 of 12 Old 07-12-2018, 10:28 AM
jtec
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reputation.... but the IQ issue was all ready known -

Anyway - did the CEL come on? likely no

I would add a can of SEAFOAM and take a nice drive - anywhere but NJ.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 12 Old 07-12-2018, 11:00 AM
Fourtrail
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Should be no problem. The dealerships do it all the time during the winter when they start the cars to melt off the windshields and forget about one of the cars they started and it runs all day/night.

80 CJ-5, 74 CJ-6, 56 CJ-5
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post #4 of 12 Old 07-13-2018, 09:24 AM
vadslram
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Not fatal but not good either. At idle it never really gets up to or stays at temp and probably never went into closed loop. You will have a little extra carbon in the cylinders and probably some cylinder washdown. Nothing an oil change and some normal driving won't fix.
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post #5 of 12 Old 07-13-2018, 12:20 PM
OldJackTheJeep
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1 get smarter friends. 2 if it doesn't get up to operating temps in 30 minutes of idling, you have system problems.
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KE5PPH
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post #6 of 12 Old 07-17-2018, 06:12 AM
vadslram
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Quote:
Originally Posted by OldJackTheJeep View Post
1 get smarter friends. 2 if it doesn't get up to operating temps in 30 minutes of idling, you have system problems.
1 If you have smarter friends that makes you the dumb one in the group (Oh no were are laughing with you not at you)
2 Even perfectly working systems don't get to full temp at idle. The systems are designed for mixed operation with loaded speeds of ~2500 rpm. At 700 rpm there is enough cooling capacity at the radiator and bypass at the thermostat to keep it closed. If you don't believe it then why have a fast idle setting in both diesels and gassers and why during cooling system flushing do the instructions say run at ~1200rpm?


Like I said not fatal though.

[QUOTE]Prime vehicles for this kind of damage is police cars. Police cars spend an inordinate amount of time idling writing tickets, filling out reports and stake outs. I have replaced many a connecting rod bearing in police car engines because of this
The other effect is not so drastic. It is an idling engine may not get hot enough to start the catalytic convert working or hot enough to run efficiently. It may also load up the catalytic converter with fuel that could lead to an early demise of the catalytic converter.
this.http://autorepair.about.com/library/a/1h/bl151h.htm
/QUOTE]

In the summer I'll idle my diesel for 10 or so minutes after long highway runs to make sure the turbo has cooled but during the winter I don't bother. At idle it won't even warm enough to heat the cabin so the 4 or 5 minutes coming into the neighborhood is plenty.
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post #7 of 12 Old 07-24-2018, 06:25 AM
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Quote:
In the summer I'll idle my diesel for 10 or so minutes after long highway runs to make sure the turbo has cooled but during the winter I don't bother. At idle it won't even warm enough to heat the cabin so the 4 or 5 minutes coming into the neighborhood is plenty.
Not meaning to get off topic, but:
It makes on difference if it is winter or summer. The idea of "cooling down the turbo" isn't to keep the turbo from being damaged, it's to insure the oil trapped in it isn't cooked after shutdown. Your post run EGT's should dictate your cooling cycle, not the outside ambient temp.

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post #8 of 12 Old 07-27-2018, 05:47 AM
vadslram
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Quote:
Originally Posted by jeepdaddy2000 View Post
Not meaning to get off topic, but:
It makes on difference if it is winter or summer. The idea of "cooling down the turbo" isn't to keep the turbo from being damaged, it's to insure the oil trapped in it isn't cooked after shutdown. Your post run EGT's should dictate your cooling cycle, not the outside ambient temp.
Because the incoming air in the winter isn't ~90 degrees. and the ambient temp in the engine compartment isn't well over 100.
The oil flow on mine is set up so the oil feed to the turbo is after the bypass filter and the oil cooler.
The synthetic oil I use won't "cook" unless the passages are well over 600 degrees AND have access to oxygen. So even the compressor side of the turbine shaft will cool well below that given a few minutes. Pretty much my EGTs max out at 1100 degrees at full load and WOT. during normal highway driving they settle about 800, By the time I ~idle into my driveway on the neighborhood road my gauge says it is ~400 even in the summer. But I don't have my engine chipped and try very hard to make sure all the BTUs go into making it go forward, not blowing coal out the back end
I may not need to idle it more in the summer but since I've had this truck since '99 and it hasn't burned a quart of oil between changes and still starts up immediately, I'll keep playing it safe.
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post #9 of 12 Old 07-27-2018, 06:24 AM
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Originally Posted by vadslram View Post
Because the incoming air in the winter isn't ~90 degrees. and the ambient temp in the engine compartment isn't well over 100.
The oil flow on mine is set up so the oil feed to the turbo is after the bypass filter and the oil cooler.
The synthetic oil I use won't "cook" unless the passages are well over 600 degrees AND have access to oxygen. So even the compressor side of the turbine shaft will cool well below that given a few minutes. Pretty much my EGTs max out at 1100 degrees at full load and WOT. during normal highway driving they settle about 800, By the time I ~idle into my driveway on the neighborhood road my gauge says it is ~400 even in the summer. But I don't have my engine chipped and try very hard to make sure all the BTUs go into making it go forward, not blowing coal out the back end
I may not need to idle it more in the summer but since I've had this truck since '99 and it hasn't burned a quart of oil between changes and still starts up immediately, I'll keep playing it safe.

Idle cool down was a technique perfected when general public turbos were brand new and oil didn't have the current standards we enjoy today. Back then combining paraffin based oil and high heat would cook the oil in the turbo after shutdown, resulting in turbo failure at best and engine failure at worst.



My point wasn't to bash how you shut down your engine, but to point out that the average operating temp of diesel exhaust is between 400 and 1250 degrees (depending on load). With those parameters, an ambient temp difference of app 50 degrees between summer and winter doesn't make much difference. given the vast amount of air they pump through the turbo at idle, it only takes a minute or two of off idle driving to bring the turbo itself down from highway temps. This is usually accomplished between the off ramp and parking, making "cool down" idle time a non issue.
That being said, there is nothing wrong with doing something that is "safer".

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post #10 of 12 Old 07-27-2018, 06:37 AM
vadslram
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This was my first highway diesel so I was a little paranoid. I got the joy of working on someones 80s GM diesel debacle so I actually got to see what happens when bad design, cheap oil and lax maintenance collide. First he noticed a lack of power then about a month later it not only wouldn't shut off but he only stopped it by stompng the brake in 4th gear. During the teardown we saw that there was so much tar in the turbo shaft passages that it stopped turning, then the added heat borked the seal on the intake side and the engine started running on leaking engine oil.
I've never needed it but I also carry a 10 lb CO2 fire extinguisher under the seat "just in case" my engine starts sipping lube oil. With an auto trans I'm not sure you can brake stall it, even running on oil.
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post #11 of 12 Old 07-30-2018, 06:44 AM
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Quote:
Originally Posted by Anthony Bruno View Post
HYPOTHETICALLY, if someone left their 2018 Jeep GC limited idling for 12 hours straight by mistake, what damage would that cause?
...asking for a friend
Probably nothing that a couple normal drives won't take care of. Back in the day I had too many shifts to count that resulted in my car idling for up to 10 hours. I doubt it did anything good for the longevity of the engine but it did t cause any immediate problems.
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post #12 of 12 Old 07-31-2018, 11:20 AM
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Most places state that idling for 1 hour is approximately the same as driving 30 miles
When I first got into construction, I would idle my truck for 8-10 hours a day because it was my generator and air compressor. Did that for a few years then bought a generator, but went back to the truck system because the generator used more fuel.
I believe that reaching operating temps depends on the vehicle, every vehicle except one that I had would reach normal temps within 20 minutes, the oddball was a 2.9 V6 with a 351w V8 radiator.
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