Do we really need to idle for 1 to 2 minutes?

jflem24 · **Posted:** Mon Oct 26, 2009 5:40 pm

Hello All,

Let me begin by saying that I do sit in the parking lot, driveway, downtown street parking and allow the Jeep to idle for 1 to 2 minutes. Admittedly, I am not nearly as anal about this as I was for the first few years of life, but, I have a question. Is this really necessary? Is so, why? I had a friend you told me that any car with a turbo should idle for a few seconds before shutoff, but was uncertain why the CRD asks for 1 to 2 minutes. I have friends that own both Dodge and Ford diesels trucks and they have never had to sit at idle after driving. Also, the same goes for the TDI.

Can excessive idling ruin your EGR valve? I had to have mine replaces to pass emissions as the valve had outright failed. The dealer told me that excessive idling can shorten the life of your EGR valve. I thought this might have been bunk, but I do only have 38K on the '05. (I am fortunate enough to be home based).

So, in combination of idling after driving...did I shorten the life of my EGR valve by following my owners manual?

Thank you,
Josh

UFO · **Posted:** Mon Oct 26, 2009 6:25 pm

Idling after driving is not nearly the problem as idling with a cold engine. Idling after a hot fast highway run allows the turbo to cool using the still-circulating engine oil. Your engine is warm and sealed, letting only the normal blow-by into the crankcase.

Nothing's going to hurt my EGR to the point where I care, it's disconnected.

stoutdog · **Posted:** Mon Oct 26, 2009 7:37 pm

I don't bother with idling unless I have just come off of a highway run... even then, meandering around a residential neighborhood is probably enough. I usually only consciously let the CRD sit and idle if I've just pulled into a truck stop for a quick bite or fuel up.

mikey1273 · **Posted:** Mon Oct 26, 2009 7:47 pm

I asked this before too.

I do idle some... not that long most of the time. I usually am in parking lots and neighborhoods before I shut it off anyway driving 30 mph or less the last few minutes of driving. so what I do is put it in park unbuckle the seatbelt grab up my stuff, (drink, cell, ect) change back to regular glasses from sunglasses if it daytime, open door and then turn off the engine.

if I am driving fast and pull off and park right away yes then a minute or two maybe more if towing is good.

ATXKJ · **Posted:** Mon Oct 26, 2009 7:52 pm

If I was on the highway - I always idle for a while.

If I was sitting at a traffic light - it's redundant

- it's not an EGR issue - it a Turbo bearing oil passage issue

if the Turbo is hot and you shut it down too soon it can cause the oil passages to overheat and clog
(theoretically the synthetic shouldn't but I'd rather not kill a turbo finding out)

if you have a real EGT - that's the best way to monitor.

tcoilburner · **Posted:** Mon Oct 26, 2009 8:22 pm

Most of my experiance is with tractors, and they are run alot harder than most any on-road engine. most of the time it would take 4-5 min. to get the egt down the less than 400 degrees to shut it off. I do not have a egt guage on my crd, but I always cool it down for 30 seconds up to 4 min. depending on the amount of right foot :twisted:

or how heavy of trailer I am pulling. I am do this to keep from having to buy a turbo. :wink:

geordi · **Posted:** Mon Oct 26, 2009 8:40 pm

I have an EGT gauge, and its located in the entrance for the turbo. Thusly, the reading is approximately 200 degrees higher (I've been told) than if I had put the probe in the exit of the turbo.

After towing a VERY heavy 6700 lb 7.5x20' enclosed car hauler about 20 miles at up to 60mph, the turbo was most likely NICE and warm. The EGT gauge hadn't been reading accurately (or was beyond the limits of the gauge) b/c it would go up to about 1250 degrees, then instantly pin itself at 1600 (the gauge max) if even a tiny bit more power was added.

At 60mph, the gauge was holding steady at about 1000-1100 degrees with that trailer. I think that is pretty good, myself. Once I stopped, it would drop to about 500 within 10 seconds and below 400 within 30 seconds.

I considered that those numbers were accurate when factoring in the heatsoak from a hot turbo, but what does the group think? Should I still be mentally adjusting for the 200 degree drop after the turbo, so that at 30 seconds the temp is more like 200?

Ripster · **Posted:** Tue Oct 27, 2009 7:00 am

One of the big factors of the GDE eco tune is the reduced turbo heat. Before I would
need to idle about a minute to bring it down to around 500 or less, Less yet if idleing
or coasting before stopping. With the GDE any amount of idle or coast and we are
easily at 400 with about 15 seconds or less sometimes. So I would say the times
everyone is mentioning are about right, with the GDE there is less heat and faster
cooling times, as the heat ranges from 200-300 less across all types of driving.
On level ground 70 mph my post EGT shows 500 which is amazing, compared to
700 or slightly higher stock with the same conditions.

naturist · **Posted:** Tue Oct 27, 2009 8:52 am

I don't have EGT gauges on either my Jetta TDI or my CRD, but I do have 130,000 miles on the Jetta and 95,000 on the CRD, including about 7500 miles towing a 5,000 lb travel trailer.

The deal is this: with a gas engine, it is really critical that you allow the turbo to cool before you shut it off. It is less so with a diesel, because the turbo runs cooler to start with. The only times a cool-down period is going to matter on your CRD is if you've been running it hard, meaning cruising at 60+ or climbing hills or towing heavy trailers. Time spent driving down city streets or getting into parking places counts as part of the cool down period, thus if you pull into a rest area straight off the freeway, a cool down period is a very good idea. But if you pull off the freeway onto a side road, and putter on into town, through a couple traffic lights, and around a block or two looking for a parking place, you have already done what needed to be done.

nursecosmo · **Posted:** Tue Oct 27, 2009 11:30 am

If you are shutting the engine off based on EGT, you may be surprised by actual temperature of the turbine housing if you check it with an infrared thermometer. The EGTs are a reflection of the combustion temps within the engine and pickup less heat from the manifold and turbo charger than you might think. If I have been running under any kind of load which I know heated up the turbo, I always let it run until I know that the snail has cooled down sufficiently. That may involve driving under light load on slow streets, or idling for a few of minutes in the rest stop parking lot.

007husky · **Posted:** Tue Oct 27, 2009 12:06 pm

there is no harm in letting it cool down .. you just loose a minute or two.

My egt is set right after the turbo... and i wait till is around 500 F before i shut it down... driving without a trailer can vary from 800-900 F if i m pushing it a bit to 600-700 normal driving... with EGR connected. when you have the egr disconnected (orm) temps go down at least 150-200 F on the egt

At our station, we had several turbo`s fail on the fire trucks... it turns out that most drivers were pushing the trucks with all the equipment water and ladders on the way home, not crazy but they were not grandma drivers... they would pull in the bay and shut it down right away... This killed a few turbo`s till the engineers were told that they need to let it idle to allow cool down, before they turn them off.

Do we really need to idle for 1 to 2 minutes?

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