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-   -   Driving in neutral bad for engine? (https://www.fuelly.com/forums/f8/driving-in-neutral-bad-for-engine-4600.html)

GasSavers_jkandell 05-22-2007 07:14 AM

Driving in neutral bad for engine?
 
I do a lot of coasting in neutral. This has me a bit worried:
"An idling engine isn't operating at its peak temperature, which means that fuel doesn't undergo complete combustion. This leaves fuel residues that can condense on cylinder walls, where they can contaminate oil and damage parts of the engine. For example, fuel residues are often deposited on spark plugs. As you spend more time idling, the average temperature of the spark plug drops. This makes the plug get dirty more quickly, which can increase fuel consumption by 4 to 5 percent. Excessive idling also lets water condense in the vehicle's exhaust. This can lead to corrosion and reduce the life of the exhaust system."
idling-myths

Hockey4mnhs 05-22-2007 08:34 AM

eoc is said to be bad for a auto tranny but other then that i havent heard much about outer things

jwxr7 05-22-2007 08:37 AM

you could turn off the engine instead of idling:) .

Fourthbean 05-22-2007 09:13 AM

I am no expert on engines, but have heard of the problems you are talking about. Though excess idling I imagine would be ALOT of idling. Not idling for a mile every 2 miles. I also would think that if you idled for a mile and then ran your engine somewhat hard afterwards you would blow out what was deposited during the idle. On the other hand if you were idling for hours I think it would be a different story.

That is my take on it. I am sure some more knowledgeble folks are typing up a reply right now ;).

Bill in Houston 05-22-2007 09:14 AM

The paragraph you quoted was written to encourage Canadian drivers not to idle to warm up their stone cold cars. Completely different from when you and I idle in neutral with a fully warmed-up engine...

rvanengen 05-22-2007 09:41 AM

Quote:

Originally Posted by jkandell (Post 52227)
I do a lot of coasting in neutral. This has me a bit worried:
"An idling engine isn't operating at its peak temperature, which means that fuel doesn't undergo complete combustion. This leaves fuel residues that can condense on cylinder walls, where they can contaminate oil and damage parts of the engine. For example, fuel residues are often deposited on spark plugs. As you spend more time idling, the average temperature of the spark plug drops. This makes the plug get dirty more quickly, which can increase fuel consumption by 4 to 5 percent. Excessive idling also lets water condense in the vehicle's exhaust. This can lead to corrosion and reduce the life of the exhaust system."
idling-myths

An idling engine should be running at NORMAL operating temperatures within a few minutes. If this weren't so, there are a LOT of police cars that would die prematurely. I just recently got rid of a used police car I picked up on ebay, and I am sure that the motor had a LOT of "donut miles" on it. Main problem that car had was just normal police pursuit and operational wear.

VetteOwner 05-22-2007 04:35 PM

driving in neutral is not bad for anything but if the engine is off coasting down hills then your goinna run into serious tranny problems

cfg83 05-22-2007 05:13 PM

jkandell -

Quote:

Originally Posted by jkandell (Post 52227)
I do a lot of coasting in neutral. This has me a bit worried:
"An idling engine isn't operating at its peak temperature, which means that fuel doesn't undergo complete combustion. This leaves fuel residues that can condense on cylinder walls, where they can contaminate oil and damage parts of the engine. For example, fuel residues are often deposited on spark plugs. As you spend more time idling, the average temperature of the spark plug drops. This makes the plug get dirty more quickly, which can increase fuel consumption by 4 to 5 percent. Excessive idling also lets water condense in the vehicle's exhaust. This can lead to corrosion and reduce the life of the exhaust system."
idling-myths

Welllllll, for Saturns, leaving the car in idle causes the engine to overheat :o , so I am guessing that combustion isn't a problem.

It would be interesting to know the "average temperature" of a spark plug, however.

I don't worry about coasting in neutral, but I do assume that I am wearing out my clutch faster.

CarloSW2

slurp812 05-22-2007 05:17 PM

Quote:

Originally Posted by jkandell (Post 52227)
I do a lot of coasting in neutral. This has me a bit worried:
"An idling engine isn't operating at its peak temperature, which means that fuel doesn't undergo complete combustion. This leaves fuel residues that can condense on cylinder walls, where they can contaminate oil and damage parts of the engine. For example, fuel residues are often deposited on spark plugs. As you spend more time idling, the average temperature of the spark plug drops. This makes the plug get dirty more quickly, which can increase fuel consumption by 4 to 5 percent. Excessive idling also lets water condense in the vehicle's exhaust. This can lead to corrosion and reduce the life of the exhaust system."
idling-myths

I blasted my car to 6000 rpm yesterday :eek: twice! but then I did about a mile EOC. But the reason I did that was because I thought I felt the car sputter when it wasnt warmed up the other day leaving a parking lot. I used to tell people cars need to be DRIVEN, not babied to death. Give that thing some gas at least once in a while. But I am leaning the other way now, in the name of saving $$$ and helping the planet just a bit. So I will still stomp it at least once per tank....

JanGeo 05-22-2007 05:26 PM

A rev is ok as it tends to loosen up the engine a little works some oil to the top of the pistons and breaks loose any carbon in the combustion chamber - I usually rev it once a trip but not flooring it just a quick rev in first gear with light throttle.

thisisntjared 05-22-2007 05:56 PM

Quote:

Originally Posted by VetteOwner (Post 52285)
driving in neutral is not bad for anything but if the engine is off coasting down hills then your goinna run into serious tranny problems

if its automatic

GasSavers_Ryland 05-22-2007 08:43 PM

You might wear out your pilet bearing, it's a $6 bearing, but you have to pull the tranny to get to it, and the ones that come with some of the new clutch kits are crap.
otherwise I don't see an advantage of keeping the engine engaged and running fast if you don't need the power, once your engine is warmed up any blow by gasses should get cooked out, along with any water, not letting an engine warm up is when you start to have problems with water in the crank case and in the exaust, the spark plugs use the head as a heat sink, so if your engine is warmed up then the plugs shouldn't foul easly, if you find that they are fouling, then go up a heat range.

VetteOwner 05-23-2007 01:43 PM

Quote:

Originally Posted by thisisntjared (Post 52312)
if its automatic

ye ai forgot to add that....u can do whatever with a manual tranny, just automatics will be toast real quick with engine off coasting;)

JanGeo 05-23-2007 03:21 PM

Pilot bearing in a manual is not getting damaged when the engine is off because it is not spinning - the clutch and flywheel and input shaft to the tranny are all stopped. The only time the pilot bearing is in use is when the clutch is held in then the input shaft with the clutch disk can be turning at a different speed than the flywheel + pressure plate + engine crank. Coasting in Neutral with the engine off the flywheel and input shaft are stationary.

GasSavers_Ryland 05-24-2007 08:34 AM

Quote:

Originally Posted by JanGeo (Post 52461)
Pilot bearing in a manual is not getting damaged when the engine is off because it is not spinning - the clutch and flywheel and input shaft to the tranny are all stopped. The only time the pilot bearing is in use is when the clutch is held in then the input shaft with the clutch disk can be turning at a different speed than the flywheel + pressure plate + engine crank. Coasting in Neutral with the engine off the flywheel and input shaft are stationary.

you're correct, at the time I was thinking about coasting with the clutch disengaged, as well as the car being in neutral so you aren't turning the main shaft of the transmition as well.

GasSavers_jkandell 05-25-2007 07:15 AM

Quote:

Originally Posted by Ryland (Post 52603)
you're correct, at the time I was thinking about coasting with the clutch disengaged, as well as the car being in neutral so you aren't turning the main shaft of the transmition as well.

So if the engine is running, and I'm moving in neutral, and the clutch is not pressed in, then I'm ruining the pilot bearing?

jwxr7 05-25-2007 07:47 AM

Quote:

Originally Posted by jkandell (Post 52743)
So if the engine is running, and I'm moving in neutral, and the clutch is not pressed in, then I'm ruining the pilot bearing?

No, there should be no movement on the pilot bearing under those conditions.

Snax 05-25-2007 07:48 AM

Let's take a quick step back: A pilot bearing is NOT the same as a clutch throw-out bearing, which is the bearing that slides along with the clutch lever up against the clutch pressure plate fingers. A pilot bearing is usually a shaft-end bearing designed to stabilize, and it is often (though not always) designed to spin as fast or slow as the engine and or transmission will normally spin.

A throw out bearing by contrast is not designed for sustained high rpm spinning, but rather only during the momentary disengagement of the clutch pressure plate when it has both axial and radial forces acting upon it. In other words, it is designed to spin only when the pressure plate is disengaged (pedal in). And because the throw-out bearing lives in the same hot dusty environment of the clutch, it is normally assumed to be a wear item that is replaced with the clutch.

It is also worth noting that many modern transmissions do not even use a pilot bearing at the end of the transmission main shaft into the flywheel.

Telco 05-25-2007 10:17 AM

Coasting engine off in a manual should be done in neutral, not clutch in. The clutch is designed as a momentary break between the engine and trans to allow gear shifting, not as a means of coasting.

Coasting in an automatic should be done in neutral, engine running as the transmission pump is driven off the input shaft, not the output shaft. Running the auto with the engine off means no tranny fluid is being pumped around, which means the output shaft is not being lubed, which will burn out bearings and pump crap through the rest of the system when the engine is started again.

If a Saturn overheats when idling, even if coasting at speed, then the water pump isn't pumping enough fluid through the engine. Either that or the thermostat isn't opening all the way.

Hope this helps...

VetteOwner 05-25-2007 10:48 PM

well you should anticipate lights and shift it into neutral and coast up to them (should know your car good enough to be able to just take it outa gear without even having to press in the clutch.(its the point thats between acceleration and engine braking) then once you see the cross traffic lights turn yellow then push in the clutch and go to first and wait.

diamondlarry 05-26-2007 04:42 AM

Quote:

Originally Posted by Telco (Post 52766)
Coasting engine off in a manual should be done in neutral, not clutch in. The clutch is designed as a momentary break between the engine and trans to allow gear shifting, not as a means of coasting.

Coasting in an automatic should be done in neutral, engine running as the transmission pump is driven off the input shaft, not the output shaft. Running the auto with the engine off means no tranny fluid is being pumped around, which means the output shaft is not being lubed, which will burn out bearings and pump crap through the rest of the system when the engine is started again.

If a Saturn overheats when idling, even if coasting at speed, then the water pump isn't pumping enough fluid through the engine. Either that or the thermostat isn't opening all the way.

Hope this helps...

A Saturn automatic will not be harmed by coasting with the engine off. Some Honda automatics can be towed as well. This is why you see so many Saturns being towed behind RV's that are being transferred from the manufacturer to thier dealers.

As mentioned above, if the Saturn overheats, check that the thermostat is opening properly or that the belt is gripping enough. A slipping belt can be the belt worn out or the belt tensioner getting weak. I found this out last year on my Saturn when I kept getting the low battery charge/overheat light with a brand new belt and the temp gauge was in the normal range.


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