Being new to diesels, I have what is probably a stupid question to 99% of the users in here. Why do we let them idle ( when warm ) everytime we stop for 10 - 15 minutes, or so ??? I am used to a gas engine that we constantly shut off everytime we stop for awhile.
Be gentle with your comments. Remember, I am a newbie to diesels.

RB :confused: :confused: :confused:

I let my Dmax cool down when finished pulling a heavy load in order to cool down the turbo. I have had it explained to me that the turbo depends on engine oil for lubrication and because it spins so fast it needs to wind down before shutting down the engine. I understand this to mean that if the engine is shutdown then there is no lube going to the turbo while it is still spinning down. I guess what it boils down to is this. A cool turbo is a happy turbo................SWH...

You’ll get all sorts of answers, some will talk about thermal cycles and starter loads, but I suspect a lot of guys leave them idling because they see the Big Boys doing it. The only reason I leave mine running is to allow the turbo to cool after a hard tow. Remember diesel cars are driven like gas cars by most people, which means they turn them off when they get where they’re going and turn them on again when they leave. Also, I believe that UPS drivers turn their trucks off at each stop. They certainly wouldn’t do that if it caused lots of expensive mechanical problems.

TC

If my truck needs to idle for more than a couple of min.,It gets tuned off.If I've been running hard,i'll wait til my EGT hits 300*and then turn it off.

but I suspect a lot of guys leave them idling because they see the Big Boys doing it.

:exactly: ):h

however in the winter its so cold here that I rarely shut it off... -15 to -20 degrees even when high idleing it cools down. It was REALLY cold one night, I was driving, engine was at operating temp (180-192) and I stopped at a store, left it high idleing in the parking lot for maybe 10 minutes, came out and saw the ECT guage had gone wayyy down. Just for kicks I plugged in the Tech 2 and ECT had gone down to 159* :eek:

I started driving and it came right back up tho. In the cold you have to work a diesel to make it warm up. Starting it and letting it idle in your driveway for 10 minutes before you drive away in the winter is not gonna help it warm up at all.

ben

:exactly: ):h

however in the winter its so cold here that I rarely shut it off... -15 to -20 degrees even when high idleing it cools down. :eek:



benHow do you like living at the North Pole Ben?:muahaha:

I ususally let mine cool down for just a few minutes. Then shut it down.
I have been known to let mine idle for a time but I don't like doing it and it is not good for them.
If you do need to let them idle, rev them up a little to around 1200 or so.

If running normal, by the time I drive down the street to my home, typically my EGT are at 300 deg. or so when I pull in to the driveway and shut it down.

If pulling heavy, I will let it idle until my EGT are in the 300 deg range.

MaxRock

I do it to be cool like the "Big Boys":rolleyes:

I don't do it, but then I don't ever tow more than 4000 lbs either.

I have had it explained to me that the turbo depends on engine oil for lubrication and because it spins so fast it needs to wind down before shutting down the engine.

This is true but not practical, you would basically have to shut your truck off at speed going down the road. by the time you hit the brakes coast to a stop, find a parking spot,gas pump ect. your at least half way to where you need to be.

I only let it idle about a min or so after towing my trailer (15000 lbs). if there was a huge problem with this they would install a Pyro from the factory.

As far as shut down and restarts we have to do it many times a day (seems like hundreds) on the Air Force Flight lines. we have some 03/05 ford PSD's -:t and I've yet to see a starter fail. But the doesn't mean it doesn't happen.

Mostly I let it idle when it's very cold out and especially if I'm doing lots of short trips. Also if the fuel is on a company bill or the truck is a company truck. You can't get in the truck to warm up if it's not running.

ive heard that if the engine is shut down with the EGTs higher then normal idle temp (300 or so) that the oil left in the turbo will burn and cause carbon buildup in the turbo. which will make the turbo fail sooner.

How do you like living at the North Pole Ben?:muahaha:

):h ):h ):h Thats a cold question....:)

ive heard that if the engine is shut down with the EGTs higher then normal idle temp (300 or so) that the oil left in the turbo will burn and cause carbon buildup in the turbo. which will make the turbo fail sooner.


yeah thats true iv been working with turbo gasers and that is one of the main resons i have turbo timers on my gasers im thinking of putting one on the dmax iv pulled apart a gaser turbo with 2200 miles that i never cooled off and and it looked like sh*t compared it to the one i gave time to cool off and that one still looked new

You’ll get all sorts of answers, some will talk about thermal cycles and starter loads, but I suspect a lot of guys leave them idling because they see the Big Boys doing it. The only reason I leave mine running is to allow the turbo to cool after a hard tow. Remember diesel cars are driven like gas cars by most people, which means they turn them off when they get where they’re going and turn them on again when they leave. Also, I believe that UPS drivers turn their trucks off at each stop. They certainly wouldn’t do that if it caused lots of expensive mechanical problems.

TC
my friend drives for ups....they shut thier trucks off for safety reasons and theft and not because of engine or mechanical stuff.

I always let mine idle for at least a min or 2 when I'm not towing. When I am towing I let it idle for at least 5min. It can't hurt, it can only help. That’s why there are turbo timers or are they just a gimmick?
When does the most ware come on an engine.... during start up. I Leave it running for the 5 min I'm in the gas station.

ive heard some say it is bad to let diesels idle. why? i drive a pete mixer with a cat c10, which ides virtually all day and doesnt seen to have any issues. :wtf1:

Most people would be shocked at the EGTemps on there diesels,I was :o: when I installed my gauges, very surprised........

I have BD-Power's X-MONITOR with digital display for pyro and boost and the added bonus with this unit is the CES (cool engine shutdown timer). I have it set for 260'F or 5 mins whichever comes first. It seems to work great. Any temps below 300'F at shutdown should be good. :) ...................

I only do it at truck pulls, thats b/c the "Big Boys" do it!

ive heard some say it is bad to let diesels idle. why? i drive a pete mixer with a cat c10, which ides virtually all day and doesnt seen to have any issues.


Leaving it idle keeps it too cold to burn all the fuel. The fuel will wash down the cylinder walls.

Oil pressure is usually low also at idle meaning it's not getting lubed very good.

The Cat engines I've been around here lately (C-9, C-15) idle at 1100 which is not too bad. The ones idling below 1000 is the ones that's bad.

I was one of the bigboys before I switched jobs so Its more of a bad habit than anything, But In the Winter its nice to be warm too!!

I leave mine idling all night when I sleep in it.

Leaving a Duramax idle is not in anyway going to wash down the cylinder walls no matter how cold it is. Your truck would have to idle for days pouring out smoke before the rings would be affected by the wash.
Duramax trucks usually idle at 25-30psi when warm, and that is more than enough to keep the engine lubed at idle without load. My street/strip car idles 10psi@ 1300rpm and runs 45psi@ 7,000rpm and has been doing that for 6years!

if you have a ZF6 extensive idling will not be very helpful. Peter of SBC recommend (primarily for DDC) to get the idle up to 900 rpms. The diesel spike will have an impact on the DMF and possibly on DDC if you do extensive idles. A Fluidampr or a sprung hub clutch plate will help but I extensive idle may still be a problem. I suspect that an allison does a better job of absorbing the spike than a DMF does.

I suspect that an allison does a better job of absorbing the spike than a DMF does.

Well seeing as the Allison's, or any automatic for that matter are fluid driven throught the torque converter, I would imagine that they wouldn't have issue's with the torsional harmonic vibration from the motor passing through the planets since it's gotta pass through the fluid first and never makes direct contact during idle ;) .

Cheers,
Wade

Some good info on why not to let your truck idle here (http://u15205752.onlinehome-server.com/forums/thread-view.asp?tid=12119&mid=80026#M80026).

Leaving it idle keeps it too cold to burn all the fuel. The fuel will wash down the cylinder walls.

Oil pressure is usually low also at idle meaning it's not getting lubed very good.

The Cat engines I've been around here lately (C-9, C-15) idle at 1100 which is not too bad. The ones idling below 1000 is the ones that's bad.
Agree 100% with what is said above, about lubrication and towing. I think the oil pressure is too low (about 20 on my truck) but they say its enough so you dont float the bearings. I usually use a 5 minute rule, under 5 leave it run over 5 shut her down. I dont think itll cool too much in 5 min to wash the cylinder walls unless it gets real cold out and hten ill have high idle on and the witner front.

Alot of truck drivers do it cause they odont pay for the fuel, know , or care. + want the truck warmed or cold fuel dosent come out of most guys pockets or reparis.

Always better to be safe then sorry.

i always let mine idle down after ive driven on the interstate or highway, usually 3 mins or till it gets close to 300egt's. as far as ideling it when i go into a store, if im in there for more than 10 mins then i usually shut it off. in the morning i let mine idle for 5-10 mins before i hop into it. ill engage the high idle if its really cold out (below 30)

I let mine idle down to 300 - 350 degrees then shut it down. If I am running into the store for a soda or something I will leave it run.

I think your engine will rev up before you wash down the cylinder walls, because the nature in the way diesel burns. Also more food for thought, we have a complicated ECM running the engine I do believe it would make the neccesary adjustments to fueling to keep wash down from happening. My LB7 has 9,000 + hours on it... a lot of that is idling....it has no problems to date.

I do it because it won't hurt it. I figure the couple of minutes idleing is better than cranking on the starter. Also, a diesel will actually cool down when idleing. Agas engine will heat up.

I think the big boys do it because the trains do.

big boys do it because they like to have a warm/cool sleeper when they bed down for the night.