Does it hurt anything? Did it by accident today. Seems ok; not overheating or anything. Thoughts?
It's a 2009 Corolla if that makes a difference.

I wouldn't worry about it. An old carbureted engine might be a different story.

No. It's a Corolla.

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.

That's a half gallon of unleaded you'll never get back

I used to do it with Diesel powered cars in very cold weather. Let it idle and lock the doors.

Never found any damage to the car.

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

quote:

Originally posted by caneau:
No. It's a Corolla.

I would add a few hundred miles to the oil change clock. Unless it has an oil life monitor and should keep up with engine hours

It shouldn't hurt anything. I would take it for a drive after it warms up and drive it a little hard (acceleration) just to clean out the engine.

A friend did it with his new Lexus SUV. Five hours. By mistake. He said he did not hear the engine, it was so quiet.

An auto reviewer wrote that he takes a new car and parks it running in his driveway over the weekend. If it is still running normally after 2-3 days, it has passed the first test. (This was something I read maybe ten years ago but generally do not read both the papers and reviewers).

What's the point in that?

It's engine specific.
Some engines at idle do not oil everything as they rely on "splash" (especially older year engines).

Some will develop hot spots as coolant flow is not optimal.

But for the most part, it is unlikely to do harm, as most engine's computers manage/monitor fuel/air systems and will keep things in correct operating parameters.

"Stop and go" city driving will result in greater impact to wear and issues than standing idle for hours.

I have never experienced a short term effect, but have no clue about a long term effect. By this I mean long term effect would be doing this a few times a week for many weeks compared to a one time thing. When doing surveillance, I have sat in a car idling for 12 hours a day for around three days sometimes in 100+ degree temperatures. I would switch to a different vehicle every couple days when doing long term surveillance so the same vehicle wasn’t parked close or following them. Never had a problem with the vehicle. Would I do that in my own vehicle? No way; just because I do absolutely everything to make my POV last as long as possible.

quote:

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.

Won’t hurt it.

I heard drive train is okay but not good for the catalytic converter?

You have nothing to worry about.

I had a company truck, a 2011 F250 gasser with an auto tranny. The engine was running 14 hours a day, 21 days out of the month. Most of that time was at idle. This went on for 2.5 years. Oil changes at 5K intervals. I quit when there was 120K on it. I had zero issues with it.

My Tundra doesn't get worked hardly as much but when I'm in the field, it doesn't like it so much. It will idle for 14+ hours a day for, at most 5 days in a row. When Temps are in the 110* bracket I don't have a choice and sometimes lane departure warning come on etc, all related to underhood heat I would imagine.

I think you're going to be fine, carry on.

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.

My '97 Corolla ran at idle in the garage one day. I started it simply because it hadn't been started in like a month. Closed the door and I'll be damned...doors locked and I didn't have an extra key or fob. Had to call a tow truck to come get it open. Ordered a spare fob when I got back inside. And car still runs like a top...