2.5 Auto diesel....idling in "D" for long periods

[Bongoplod]

It may have been covered before, but having read MikeonB4C`s reply to another post,he mentions starting his Bongo (2.5 auto) these cold mornings and leaving it in D to warm the gearbox,and goes back in for a brew .

Now I know autoboxes dont have a clutch,but is it OK to leave it in D for long periods without
causing amy harm to the gearbox/torque system?

Its been mentioned that leaving it in D at traffic lights is preferable to the wear and tear that is caused by selecting PARK then moving back to D,but Ive always wondered if leaving it in D at traffic lights and in long traffic queues for LONG period,may do some harm.

Anyone can enlighten me (Dandy,any thoughts?)

Brian

[mister munkey]

From a Numpties viewpoint it makes sense to me. Idling in D is pretty much a No Contact Sport, as far as I can see.


Getting the lube thinned & runny makes sense before subjecting any moving parts to stress.

[nfn]

My wife spent her late teens and early 20s in Minnesota, which is seriously cold in winter. She is of the school of thought where you start the car 20 minutes or so before you get in it and go. They don't leave it in D because the handbrake can easily become stuck frozen -- so the handbrake is not used in winter (actually North Americans tend to never use the handbrake unless parked on a steep hill, regardless of time of year). The main reason for starting the car up 20 minutes early is not mechanical -- it's done so the interior warms up a bit. Mechanically, surely you should just get in and go, warming it up fast without using excessive rpm. This should minimise engine wear by reducing the amount of time the engine is running cold/cool. There's also a small risk that something will go wrong while the engine is running and you're not in the car -- with a bongo probably cooling system related.

The bongo transmission has a built-in rapid warm-up procedure of not going into overdrive until warm, which should be enough to reduce wear in cold weather. For both the engine and trans I'd say you should just get in and go in winter.

[mikeonb4c]

My wife spent her late teens and early 20s in Minnesota, which is seriously cold in winter. She is of the school of thought where you start the car 20 minutes or so before you get in it and go. They don't leave it in D because the handbrake can easily become stuck frozen -- so the handbrake is not used in winter (actually North Americans tend to never use the handbrake unless parked on a steep hill, regardless of time of year). The main reason for starting the car up 20 minutes early is not mechanical -- it's done so the interior warms up a bit. Mechanically, surely you should just get in and go, warming it up fast without using excessive rpm. This should minimise engine wear by reducing the amount of time the engine is running cold/cool. There's also a small risk that something will go wrong while the engine is running and you're not in the car -- with a bongo probably cooling system related.

The bongo transmission has a built-in rapid warm-up procedure of not going into overdrive until warm, which should be enough to reduce wear in cold weather. For both the engine and trans I'd say you should just get in and go in winter.

I reckon that's pretty much right nfn. I use a wheel chock of course and I wouldn't do the 'D' trick on a public highway either.

I start the car to warm and defrost windows, as you say (although I think a minute or two on tickover could well be good for a big diesel as I know mine can stutter occasionally right after startup on cold/damp mornings). It makes sense to recover some of the fuel cost by putting it in 'D' at the same time as otherwise I find the gearbox behaves more or less as though you'd not warmed it at all. The result is a fuel inefficient few minutes while it runs at 2500 rpm in order to do about 30mph (that rpm would normally give around 65 mph in top gear lockout).

I think the safety issue is the one that requires the most careful thought. I'm clear in my own mind about the attractions otherwise.

PS - we're snowed in here this morning or I wouldn't be on here

[dave_aber]

Its been mentioned that leaving it in D at traffic lights is preferable to the wear and tear that is caused by selecting PARK then moving back to D,but Ive always wondered if leaving it in D at traffic lights and in long traffic queues for LONG period,may do some harm.

Anyone can enlighten me (Dandy,any thoughts?)

I'd like to hear any clarification on this too. My Bongo is my first auto, so I'm still getting used to it. (I did stick my Astra Van in reverse the other day without using the clutch, so I must be getting used to the auto now!!)

Whenever I stop at junctions / lights / etc, I move from D to N, as it seems more mechanically sympathetic than sitting in D with the vehicle straining -gently- against the brakes. Only downside is if you forget, and rev up before selecting D, and then (with brain in 'N') move from N to D at 2000rpm. Not smooth!

So what's the observed wisdom of the forum?

[mikeonb4c]

Its been mentioned that leaving it in D at traffic lights is preferable to the wear and tear that is caused by selecting PARK then moving back to D,but Ive always wondered if leaving it in D at traffic lights and in long traffic queues for LONG period,may do some harm.

Anyone can enlighten me (Dandy,any thoughts?)

I'd like to hear any clarification on this too. My Bongo is my first auto, so I'm still getting used to it. (I did stick my Astra Van in reverse the other day without using the clutch, so I must be getting used to the auto now!!)

Whenever I stop at junctions / lights / etc, I move from D to N, as it seems more mechanically sympathetic than sitting in D with the vehicle straining -gently- against the brakes. Only downside is if you forget, and rev up before selecting D, and then (with brain in 'N') move from N to D at 2000rpm. Not smooth!

So what's the observed wisdom of the forum?

Leave it in 'D' unless it is a really extended stop esp. if in hot weather. 'N' may save a tad on fuel, and it may keep the box a little cooler when stationary, but I reckon regular clonking into and out of 'D' could build its own legacy of wear damage over time. And it isn't pleasant (though holding the footbrake on whilst doing it seems to all but eliminate the clonk)

[Diplomat]

Glad I'm not the only one whose gearbox is extremely sluggish in this cold.

It's the first time I've really noticed it. Normally I get into lock up about a kilometre down the road in winter, half that in summer. At the moment it doesn't even want to get out of third.

With regard to using "P" at lights etc. I would never do it as it turns the vehicle into an immovable object if hit up the rear. Much more damage, much more whiplash.


Frank

[mikeonb4c]

Glad I'm not the only one whose gearbox is extremely sluggish in this cold.

It's the first time I've really noticed it. Normally I get into lock up about a kilometre down the road in winter, half that in summer. At the moment it doesn't even want to get out of third.

With regard to using "P" at lights etc. I would never do it as it turns the vehicle into an immovable object if hit up the rear. Much more damage, much more whiplash.


Frank

Nah the sluggishness is normal. Lets face it, the Bongo is best when (a) its engine has warmed up and (b) it hits the open road. Its just that - for a campervan type vehicle - it has to be one of the best for still using as a normal car.

Your point about not using 'P' is a very important one I think. I hate to think what damage could result from shock loadings going into the gearbox (I assume that is what happens). 'P' is for 'parking', 'N' is the one I always use if I do want to disengage the box in traffic etc.

[mikexgough]

I tend to not have an issue, as we are fairly flat here, start from cold in P....clear windows of frost or dew....jump in, engage D (dependent of the road and snow/ice) and away ...less than 2 mins..... after about a mile 1/2 .....warm enough for "lock up....oh and I tend to hit traffic in 300 yds to crawl for a mile in D.... which is probably the same/similar as Mike's engine running in D and inside for a Brew....

[BONGOCONGO]

Have driven autos for some years now - a Cavalier which covered over 130 k before I let it go but it was still changing smoothly. I currently own a Mazda 626 which has been in my family since 1998 and which I've driven for over 8 years. This car was bought new by my Dad and then onto me. It has also covered over 100k and is as good as the day it was bought. I ALWAYS move the selector into N when I come to rest at lights etc unless I see I am going to move off in seconds. I have recently bought a Bongo and will continue to drive this the same way. Mazda boxes are great in my experinece - very smooth changes throughout. I haven't had the experinece yet of sluggishness etc as I haven't driven it much in this cold weather so others with more experience may know better than I do with respect to Bongos.
Of course, leaving your engine running and going indoors for a cuppa, unless you live in a remote house, will invalidate your insurance if it's nicked from the drive while you sup!!!!

[mikeonb4c]

Have driven autos for some years now - a Cavalier which covered over 130 k before I let it go but it was still changing smoothly. I currently own a Mazda 626 which has been in my family since 1998 and which I've driven for over 8 years. This car was bought new by my Dad and then onto me. It has also covered over 100k and is as good as the day it was bought. I ALWAYS move the selector into N when I come to rest at lights etc unless I see I am going to move off in seconds. I have recently bought a Bongo and will continue to drive this the same way. Mazda boxes are great in my experinece - very smooth changes throughout. I haven't had the experinece yet of sluggishness etc as I haven't driven it much in this cold weather so others with more experience may know better than I do with respect to Bongos.
Of course, leaving your engine running and going indoors for a cuppa, unless you live in a remote house, will invalidate your insurance if it's nicked from the drive while you sup!!!!

Interesting you say that. I have always put my manual cars in neutral when I stop, and was inclined to do the same when I got my first auto, the Bongo. But opinion on here was strongly against that (including one professional driver who had always left his vehicles in 'D' with no bad result, and another who made the valid point that having an automatic was about having an automatic). I was for saving fuel by putting it in to 'N' at lights (and indeed I started with this habit). But again, I was advised the saving would be minimal. What really decided me was that I disliked the clunk each time I engaged 'D' in readiness to move off when the lights changed etc. I reckoned it was more damaging than leaving the box in 'D' so I applied similar reasoning to the one I used for not leaving a manual car in gear, with clutch depressed.

Hopefully, the tea-leaves are no more likely to nick mine with engine running than engine off as I leave the steering lock on and lock the car with the spare keys.

[dandywarhol]

I don't see any advantage in idling in D. With the brakes on the only difference between D and N is the front clutch is applied but nothing else is working/turning. In fact, idling in N will probably warm up the oil faster as the torque convertor is running/slipping a little faster.

Sitting in D at the lights does no harm whatsoever

[mikeonb4c]

I don't see any advantage in idling in D. With the brakes on the only difference between D and N is the front clutch is applied but nothing else is working/turning. In fact, idling in N will probably warm up the oil faster as the torque convertor is running/slipping a little faster.

Sitting in D at the lights does no harm whatsoever

Thats interesting. I assumed it had to be in 'D' for the magic to work, but are you suggesting 'N' would do just as well? It would clearly be a less controversial option if so. But then again, the revs drop when you move from 'N' to 'D', which suggest to me the engine is dissipating more work energy into the box and thus will also generate more heat energy. I'll have to try experimenting with 'N' (think I'd still chock the car though in case the stick got knocked).

What I can say with certainty is that moving the box into 'D' whilst warming the engine/car on idle gets the box ready for lockup in top much sooner after moving off than if it is left in 'P'

[dandywarhol]

When in N, drive comes from the torque convertor into the gearbox via a multiplate clutch pack. The clutch pack is disengaged in N (much like a motorcycle multiplate clutch). In this position the oil is picked up in the torque convertor, idles around inside it warming up and is pumped around the gearbox valves and hardware also warming it up.

When D is selected, the clutch pack engaged, trys to create a solid drive through an epicyclic geartrain but can't because the brakes are on, so it just sloshes around the torque convertor and gearbox. There could be a little extra heat build up in the torque convertor in D now that I think about it, it certainly heats/overheats the oil if revs are applied with the brakes fully on! - difficult to know if it produces that much more at idle. There's probably more chance of doing mischief if someone inadvertantly stepped on the throttle, chocked or not! the torque convertor does just as it says - converts torque - and multiplies it by as much as twice at low revs - thats why they're so quick off the mark compared with manual boxes

http://auto.howstuffworks.com/automatic ... ission.htm

[mikeonb4c]

When in N, drive comes from the torque convertor into the gearbox via a multiplate clutch pack. The clutch pack is disengaged in N (much like a motorcycle multiplate clutch). In this position the oil is picked up in the torque convertor, idles around inside it warming up and is pumped around the gearbox valves and hardware also warming it up.

When D is selected, the clutch pack engaged, trys to create a solid drive through an epicyclic geartrain but can't because the brakes are on, so it just sloshes around the torque convertor and gearbox. There could be a little extra heat build up in the torque convertor in D now that I think about it, it certainly heats/overheats the oil if revs are applied with the brakes fully on! - difficult to know if it produces that much more at idle. There's probably more chance of doing mischief if someone inadvertantly stepped on the throttle, chocked or not! the torque convertor does just as it says - converts torque - and multiplies it by as much as twice at low revs - thats why they're so quick off the mark compared with manual boxes

http://auto.howstuffworks.com/automatic ... ission.htm

Interesting stuff that

I'll try putting it in neutral and seeing if I get a similar benefit to 'D'

Oh and you're right about stepping on the throttle. The other day I drove off and wondered what the bump was as I did so. I'd forgotten to remove the chock of course