Back in the 80's we'd idle gas carbed pickups all night as we monitored gas well graphs ..... They'd start running terrible in a month.
I'm not a mechanic. I haven't a clue why.

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It's a 2009 Corolla if that makes a difference.

This caught my eye because I have the same car, with 156,000 miles on it. And no, it won't harm a thing if everything is in good working order. The biggest stress on the engine would be the cooling system, but as long as it is full and clean and the electric fan operates as it should, no problemo.

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Originally posted by marksman41:
With diesel engines, is "cylinder wash" (I think that's the correct term) a concern when idling for extended periods?

Yes, I always had thought you can let a diesel run all day without a problem. That was the old diesels. Todays modern diesel should not be left at idle for an extended period. Diesel wash after allowing a diesel to run will make the cylinder walls coated with burnt oils, and resulting in oil blow by. When I first bought a new diesel pickup I had never heard of this. I spent many an hour researching this. Even when I was driving a Concrete truck which we left running all day and we got new trucks with modern engines we were told to turn our trucks off when sitting for lunch to prevent diesel wash.

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Originally posted by jhe888:

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Originally posted by mrvmax:
Some mechanics claim it can melt components under the hood from all the heat. Some professions do it all the time so it can’t be that bad.

But driving it for several hours doesn't melt it?

It just burns gas to no end.

I think ha has 50 years of mechanic experience but you can believe whatever you choose to:
https://m.youtube.com/watch?v=i4W03Xn2FSY

I lost a friend in high school decades ago to exhaust toxins from letting his February date night heater run while they were inside the car.

We have some trucks at work that idle... a lot. It's fun to play with the odometer/computer and see the estimated MPG it's getting. (like 4 MPG lol) I tell people the milage on our trucks is like dog years.

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Originally posted by Woodman:
A friend did it with his new Lexus SUV. Five hours. By mistake. He said he did not hear the engine

I did the same thing the first time I drove my parents new Toyota Highlander.

Left it on for 6 hours!

was the air conditioning on ?

The exhaust will kill shrubbery.

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Originally posted by jhe888:

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Originally posted by mrvmax:
Some mechanics claim it can melt components under the hood from all the heat. Some professions do it all the time so it can’t be that bad.

But driving it for several hours doesn't melt it?

It just burns gas to no end.

Biggest difference between the two being the rush of fresh air while driving, as opposed to idle air constantly heating while sitting.

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Originally posted by rtquig:

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Originally posted by marksman41:
With diesel engines, is "cylinder wash" (I think that's the correct term) a concern when idling for extended periods?

Yes, I always had thought you can let a diesel run all day without a problem. That was the old diesels. Todays modern diesel should not be left at idle for an extended period. Diesel wash after allowing a diesel to run will make the cylinder walls coated with burnt oils, and resulting in oil blow by. When I first bought a new diesel pickup I had never heard of this. I spent many an hour researching this. Even when I was driving a Concrete truck which we left running all day and we got new trucks with modern engines we were told to turn our trucks off when sitting for lunch to prevent diesel wash.

Actually it's not good for either new or diesels. They will load up with fuel and it can cause the cylinder walls to wash out and excessive wear/scoring and dilute the oil with fuel. The newer diesels are better about regulating fuel at idle than the new ones and can actually tolerate it better. How much excessive wear is anyone's guess and in most diesel engines it didn't seem to be a big deal. The only engines I know of that it really shortened life on were Detroit Diesel 92 series engines.

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Originally posted by erj_pilot:
OK...I'll be the one to ask. How did you "accidentally" let the car run at idle for hours? Obviously you were parked somewhere.

"Accidentally" does not need to be in quotes; it was accidentatal. I am asking myself the same question of how I could have done that, but I did. I was distracted by an unusual situation as I pulled up at work and didn't turn off the engine immediately. Then gathered my stuff, got out, locked the door, and went inside. Astonishing, I know, but there it is.

Drive home was uneventful, and all seems well. Thanks for replies.

We used to leave our patrol cars idling for hours on end...

I had a Chevy Caprice, and three different Crown Vic’s in my career...it never hurt them.

Granted they were always in the city garage for something or another, but mostly the last three cars had issues with vampire drain with all the electronics on our days off...couldn’t keep it charged enough to start on day three....city didn’t want to buy them from the factory with the extra battery and bigger alternator...

The k9 guys would alwYs pop the hood so the ac wouldn’t die...

I've got a 2012 Jeep Grand Cherokee V8 with 166,000 miles on it and 6,300 hours on the engine. It's idled for many, many days over its life and is still running strong. The only mechanical issue was with a water pump going bad at 105k and the 5.2L Hemi motors are known for that.

To seal the deal entirely, due to my error or an electrical glitch (my Jeep has had several over it's life), I once left her running at an airport when I went on a business trip. Yes that's correct, left it on and idling with about 1/3-1/2 a tank of gas in it! When I came home several days later the tank was bone dry and I had fried the fuel pump. Replaced that fuel pump and the engine is still running strong. So as you can imagine, I'm going to go with not worrying about extended idling.

Here’s a dumb story ...

A decade or more ago, worked all day, then met a friend for dinner, got home around 9 PM, and crashed. Woke up at 6 AM, shower, shave, get dressed, and walk to the kitchen ( which is attached to the garage ) and hear my 2001 Yukon Denali idling. I’m like WTF... Open the house door and it just reeks and the garage door is closed.

I hit the garage door opener and go in the house and start sweating - thinking I could have died from 9 hours of exhaust fumes if they would have leaked into the house ( 1500 sq ft patio home ).

Truck was fine and no alcohol was involved. As I said, dumb story.

MDS

I have to do it in the Summer with my work van to keep my 'employee' cool while I'm working...

What do you think police cars do? They idle for hours and then race around at mach speeds. They do this for 150K miles 24/7 then get auctioned off to cab companies to drive for another 200K miles. You have no worries.

I had a police car that basically idled for 8 hours a day. My current family vehicle idles for 1 hour every day in the car pickup line at school, doesn't do any real harm.

Your car is fine.

 
K-9 officers leave their car on all the time for the AC, for the dog. They usually have some sort of heat alarm that will notify them while they're in getting coffee or otherwise away from the car. For a long idle period, they usually raise the hood to aid air flow in the engine compartment.