Short Commute Diesel

Big Nasty

I'm no mechanic but am aware of potential longterm issues with buying modern diesels for short commute, i.e. short hop to work, picking up the kids from school, running to the shops type of driving.

I've seen the terms DMF and DPF thrown around as potential issues with diesels on short hops. Can anyone explain to me exactly why a modern diesel car is not suitable for continuous short journeys?

vectra

MCMLXXV wrote: »

I'm no mechanic but am aware of potential longterm issues with buying modern diesels for short commute, i.e. short hop to work, picking up the kids from school, running to the shops type of driving.

I've seen the terms DMF and DPF thrown around as potential issues with diesels on short hops. Can anyone explain to me exactly why a modern diesel car is not suitable for continuous short journeys?

DPF gets choked up from pottering about. keeping it between 2k and 2.5k revs ( On a VAG anyhow ) helps to avoid problems I am informed.

DMF,
From what i understand these give early problems form people changing up too soon and end up with the engine laboring.

Again I am informed to keep the revs up a bit
ie. Drop a gear.

I stand to be corrected.

DPF will clog unless it gets to burn off the particles, it won't on short spins. I reckon DMF is just a sh1t feature that can fail due to an inherent design weakness, ie it should be solid

A DMF failed on a new ish Mondeo I had as a company car at 10/15K miles, it had done hardly any urban mileage.

TheAnswer

RoverJames wrote: »

I reckon DMF is just a sh1t feature that can fail due to an inherent design weakness, ie it should be solid

Sh1t feature? Hardly. They help cancel out vibrations and failures are usually caused (as Vectra quite correctly points out) by drivers short shifting at very low revs which can bring the engine to the point of stall which places undue loads and stresses on the DMF, I've known quite a few drivers replace the DMF with a solid one and had other engine components/brackets fail tru excess vibration. Plus they've had to put up with a less refined vehicle.

TheAnswer

TheAnswer wrote: »

.........failures are usually caused ......... by drivers short shifting at very low revs which can bring the engine to the point of stall

Hardly me thinks.

Nonoperational

Ive always thought there must be an aspect of driving style involved in the whole DMF thing. It's so so variable when they go. Obviously 10/15K is a faulty part but on a standard diesel they seem to go from 60-200k.

Reloc8

gpf101 wrote: »

Ive always thought there must be an aspect of driving style involved in the whole DMF thing. It's so so variable when they go. Obviously 10/15K is a faulty part but on a standard diesel they seem to go from 60-200k.

I'd be interested to hear views on this too - like yourself I see stories of them going across a range of models at ridiculously variable mileages.

Gael23

My grandad will only drive diesel and does on average 12k a year,mainly made up of town driving and a weekly return trip from New Ross to Waterford. Last year he bought the new VW Polo TDI and so far has had no issues with the DPF with about 16k on the clock. Every so often the light comes on the dash and you get that horrible sulphur smell which the dealer told him is the cleaning process.

Nissan doctor

Driving style can effect the life of DMF's for sure, but that doesn't change the fact that they have turned a part that used to last the life of the car into a very expensive wearable part.

As an example of driving type effecting it though, I used to have a Navara that I put over 100k on, 90% motorway/national road driving, without a single DMF/clutch issue, yet in work I have a customer who uses their Navara for deliveries around Dublin city and is now on their third clutch and third flywheel in almost 80k. At the last clutch change we fitted a solid flywheel as it was simply more suited to the type of driving they were doing.

With regards to DPF's, they are mainly a feature to keep EU legislators off the manufacturers backs. They have been fitted to most of the latest diesels but since no one in Ireland ever reads the manual that comes with their car, they have no idea how to get the best from it. There are also different types, some need a certain amount of higher rpm driving to keep clean, some don't, but again, unless you do alot of research into what system the car you are planning to buy has, you won't know how suited it is to the type of driving you will be doing.

My problem with all these latest system fitted for emissions/fuel economy or whatever is that they make cars too highly strung. IMO cars should be able for whatever driving you choose to do in it within the bounds of normal roads.

Big Nasty

What exactly is DMF and DPF?

What sort of money are you looking at when they go? (Average)

Is this problem primarily caused by short hop drives / short shifts, etc?

MCMLXXV

MCMLXXV wrote: »

What exactly is DMF and DPF?

What sort of money are you looking at when they go? (Average)

Is this problem primarily caused by short hop drives / short shifts, etc?

Dual Mass Flywheel and Diesel Particulate Filter.

DMF can be €1000 upwards.

Nissan doctor

MCMLXXV wrote: »

What exactly is DMF and DPF?

What sort of money are you looking at when they go? (Average)

Is this problem primarily caused by short hop drives / short shifts, etc?

DMF = Dual mass flywheel.

DPF = Diesel particulate filter.

They both tend to head towards the 1k mark to replace when they go wrong.:eek:

GTE

RoverJames wrote: »

Hardly me thinks.

I could be a contributing factor. If you go around the city never going over 2000 revs then the filter stood less of a chance in the first place with temp and I think I read the engine has to be above a certain rev before it can do a regeneration.
Anyway, I agree with you in reality. The filter is shagged if you do general city driving in the first place. Short shifting wont help but I dont see it as the cause.


Just reading the point about manufacturers turning a life long part into almost a wear and tear item.
What is the alleged advantage to a dual mass over a solid flywheel (single mass as I see in shops)?

Big Nasty

RoverJames wrote: »

Dual Mass Flywheel and Diesel Particulate Filter.

DMF can be €1000 upwards.

Ok. so DPF is an expensive filter that can clog due to short commute / short shift?

And DMF is an advanced (or maybe not) flywheel?

What causes the DMF to go?

shedweller

bbk wrote: »

What is the alleged advantage to a dual mass over a solid flywheel (single mass as I see in shops)?

Cuts down vibrations from the engine. I would have thought a bit of reprogramming the ecu would achieve that.

sentient_6

shedweller wrote: »

Cuts down vibrations from the engine. I would have thought a bit of reprogramming the ecu would achieve that.

how? I would've thought extra engine vibration(compared to a petrol) is an inherent property of a diesel engine. EDIT: i.e nothing to do but try cancel it out.

Nissan doctor wrote: »

As an example of driving type effecting it though, I used to have a Navara that I put over 100k on, 90% motorway/national road driving, without a single DMF/clutch issue, yet in work I have a customer who uses their Navara for deliveries around Dublin city and is now on their third clutch and third flywheel in almost 80k. At the last clutch change we fitted a solid flywheel as it was simply more suited to the type of driving they were doing.

I'd have to wonder if its more than just city driving with that customer & more him riding the sh*te out of it though? Seems a bit excessive?

vectra

MCMLXXV wrote: »

Ok. so DPF is an expensive filter that can clog due to short commute / short shift?

And DMF is an advanced (or maybe not) flywheel?

What causes the DMF to go?

The short shifting is not good for the DMF/DPF

I am not 100% certain what actually causes the DMF to go as they just apparently go when they feel like it.
BUT
I did hear that short shifting and Laboring is Bad for them so avoid that driving style.

The DPF is a filter which can be replaced
OR

Removed for possibly less than half the cost of a new one,to provide a much friendlier engine
Both in Power return and Driveability.

Big Nasty

vectra wrote: »

i think you got a bit confused there
The short shifting is not good for the DMF

The DPF is a filter which can be replaced
OR

Removed to provide a much friendlier engine
Both in Power return and Driveability.

I am confused!

A clogged filter I can understand.

We're always hearing about the 'dreaded DMF problems' - I just want to understand what is a 'DMF' problem, what actually happens when a DMF 'fails' or 'goes' or whatever and what causes it to fail in the first place.

I've also seen people imply that DPF and DMF failure in 3-4 year old cars will make them almost impractical to fix.

sentient_6

MCMLXXV wrote: »

I am confused!

A clogged filter I can understand.

We're always hearing about the 'dreaded DMF problems' - I just want to understand what is a 'DMF' problem, what actually happens when a DMF 'fails' or 'goes' or whatever and what causes it to fail in the first place.

I've also seen people imply that DPF and DMF failure in 3-4 year old cars will make them almost impractical to fix.

This makes for interesting reading:

http://www.honestjohn.co.uk/forum/post/index.htm?t=84209

TheAnswer

TheAnswer wrote: »

Sh1t feature? Hardly. They help cancel out vibrations and failures are usually caused (as Vectra quite correctly points out) by drivers short shifting at very low revs which can bring the engine to the point of stall which places undue loads and stresses on the DMF, I've known quite a few drivers replace the DMF with a solid one and had other engine components/brackets fail tru excess vibration. Plus they've had to put up with a less refined vehicle.

bbk wrote: »

I could be a contributing factor. If you go around the city never going over 2000 revs then the filter stood less of a chance in the first place with temp and I think I read the engine has to be above a certain rev before it can do a regeneration.
Anyway, I agree with you in reality. The filter is shagged if you do general city driving in the first place. Short shifting wont help but I dont see it as the cause.

What you say is true bbk, but my comments were in response to a comment about the DMF, not the DPF

Big Nasty

sentient_6 wrote: »

This makes for interesting reading:

http://www.honestjohn.co.uk/forum/post/index.htm?t=84209

The whole DMF obsession on this forum is completely out of control. Yes, the odd one gives trouble but the vast majority do not. Many manufacturers have been fitting them for decades and no one knew what they were as they never went wrong.
I've come across many S40/V50 Volvo's with well over 100k on perfect DMF's so they are not a common failure point and one failing early is obviously a one off.
To be honest, on the list of expensive and common things which fail on modern, complicated cars I'd put DMF a long, long way down my list of things to worry about. Virtually all cars - including petrols - have them so are virtually impossible to avoid unless you get an auto (which have their own set of expensive issues).
There are one or two common models and makes which the DMF's are simply badly designed and poor quality on. This does not mean a DMF is an industry wide issue.

So it's a myth?:p

MCMLXXV

MCMLXXV wrote: »

So it's a myth?:p

Nope it's not, they are on some petrol cars for years, on diesels they fail. Not uncommonly either.

Big Nasty

RoverJames wrote: »

Nope it's not, they are on some petrol cars for years, on diesels they fail. Not uncommonly either.

Ok, and this is directed at RJ only, so say for example I have a new Clio that cost me €9k under scrappage. I drive the car to and from the shops, pick the kids up from school and do the odd long distance hike.

What is the likelyhood of DMF failure a couple of years down the road?

sentient_6

MCMLXXV wrote: »

So it's a myth?:p

I dunno! All i do know is i've 150k's put up on my 'modern diesel' without a clutch or flywheel issue yet (touch cheap wood).

Seemingly a more common issue i think on VW's/Audi the last few years. But i think its cos this country is VW/Audi obessed, therefore more way more cars of that brand on the road, if a certain percentage of those have issues your going to hear alot more about it.

I.e 1% of all passats/a4's is alot more cars than 1% of, i dunno, lexus for instance.

Why is it directed only at me?

Anyway, it's like asking what is the likelyhood of the fan belt snapping if you don't change it as directed.

I don't think a Clio has a DMF anyway.

Big Nasty

RoverJames wrote: »

Why is it directed only at me?

I'm trying to understand the issue and getting multiple answers, you're online right now and I trust your opinion - simple as.

RoverJames wrote: »

Anyway, it's like asking what is the likelyhood of the fan belt snapping if you don't change it as directed.

I don't think a Clio has a DMF anyway.

Doesn't have to be a Clio - that was just an example!

Seems to me that the 'dreaded DMF problem' is a bit exaggerated?

MCMLXXV

MCMLXXV wrote: »

I'm trying to understand the issue and getting multiple answers, you're online right now and I trust your opinion - simple as.



Doesn't have to be a Clio - that was just an example!

Seems to me that the 'dreaded DMF problem' is a bit exaggerated?

Well using Nissan Doctors data, Navara on the motorway no issue, Navara on urban spins 3 DMFs.

My own opinion is that the predominant factor with DMFs is the actual design, the fact that they are dual mass. Solid flywheels don't fail in any numbers to mention.

Regarding the DPF, I wouldn't buy a car with one unless I was on the motorway for a 50/100 mile spin every week.

Henry Ford III

I wouldn't buy a diesel car for urban stop start work. During the winter it takes a couple of miles for the heater to work. Petrol engines warm up much quicker.

Some take so long to generate excess heat there are auxiliary heater yokes fitted.

opinion guy

Seems like there problems can be avoided by driving with a bit of ooomph

Big Nasty

RoverJames wrote: »

Well using Nissan Doctors data, Navara on the motorway no issue, Navara on urban spins 3 DMFs.

My own opinion is that the predominant factor with DMFs is the actual design, the fact that they are dual mass. Solid flywheels don't fail in any numbers to mention.

Regarding the DPF, I wouldn't buy a car with one unless I was on the motorway for a 50/100 mile spin every week.

Now we're getting somewhere!

So DPF has a tendency to clog with short commute driving and can cost up to €1k to replace. Correct?

DMF is there to make the engine / tranny partnership more smooth than a solid flywheel? But has a tendency to fail more regularly than a solid because.....?

Is the DPF not an unnecessary filter added to meet regulations? If so surely the car would run fine if not better if it was simply removed altogether.

voxpop

The dual mass flywheel has a spring to dampen the vibration - the spring wears, which causes more play, which causes more wear, and on and on. Driving the car smoothly can alleviate this wear.

Tbh diesel have dmf, clutchs and turbos - all will need replacing cause of the mileage that gets racked up on diesels - depending on how much you spend on fuel, 6 months or a year will have saved you what it will cost to change one of the above - you may never see any of them fail during your ownership - some ppl see all three fail.

BTW - clutch and dmf on a 1.9 passat is 480stg parts and labour - so its not the super killer expense ppl make out.

Sunny Cuddly Piccolo wrote: »

Is the DPF not an unnecessary filter added to meet regulations? If so surely the car would run fine if not better if it was simply removed altogether.

DPF can be removed - the dpf is like and extra CAT, scrubs up the emissions a bit more

edit : Link with pics DPF removal

voxpop

voxpop wrote: »

DPF can be removed - the dpf is like and extra CAT, scrubs up the emissions a bit more

I thought so. Removing it and then reinstalling for the nct if required is surely the way to go so.

Big Nasty

Ok, so these theories of modren diesel cars becoming uneconomical to repair a few years down the road is plausible?

Potential problems compared to petrol models are:

DPF
DMF
Clutch
Turbo

If all or a combination of the above are to fail on a, say 4 year old car it's potentially an economic write off?

GTE

RoverJames wrote: »

What you say is true bbk, but my comments were in response to a comment about the DMF, not the DPF

OMG SOZ! lol!

All these letters. My bad!:)

MCMLXXV

MCMLXXV wrote: »

Ok, so these theories of modren diesel cars becoming uneconomical to repair a few years down the road is plausible?

Potential problems compared to petrol models are:

DPF
DMF
Clutch
Turbo

If all or a combination of the above are to fail on a, say 4 year old car it's potentially an economic write off?

Well if the car is serviced frequently the turbo should be ok , it's unlikely the DMF and the DPF would fail together, even if they did, €3000/€4000 wouldn't make many four year old cars an economic right off.

Are you thinking of buying one of the modern diesels?

200motels

The long and short of it is buy a petrol car. They are far superior and that's only my opinion.

Big Nasty

RoverJames wrote: »

Well if the car is serviced frequently the turbo should be ok , it's unlikely the DMF and the DPF would fail together, even if they did, €3000/€4000 wouldn't make many four year old cars an economic right off.

Are you thinking of buying one of the modern diesels?

God no! :eek:

I've just seen it mentioned here and on other forums alot and I want to understand it. You don't ask, you don't know!

Going back to my €9k Clio example (DMF or no - this is hypothetical), how much would one of those be worth in 2015? A €4k bill would more than likely make them an economical right off, no?

Big Nasty

200motels wrote: »

The long and short of it is buy a petrol car. They are far superior and that's only my opinion.

Along with DPF, DMF, etc I've heard the above said many times. I want to understand why!

voxpop

MCMLXXV wrote: »

a few years down the road is plausible?

more like 10-15 years


Clutch and dmf issues are just wear - diesels have more torque are so can be harder on the clutch and dmf. Drive a big torquey petrol and you will prob have some clutch and dmf issues after 150k miles also.

Turbo will be ok with good oil its whole life unless there is an inherent flaw, like recent diesel bmws

Dpf needs a decent run once a month - if you are an old lady who just goes 10 mins to the shop, the dpf will give issues as it cant burn off otherwise it will be fine or just get it removed.


On top of all this - if we are talking modern cars - many modern petrols also have turbos and have gotten complicated. A modern petrol could still have turbo,clutch and dmf issues.

MCMLXXV

MCMLXXV wrote: »

Going back to my €9k Clio example (DMF or no - this is hypothetical), how much would one of those be worth in 2015? A €4k bill would more than likely make them an economical right off, no?

Touch and go I suppose, if the diesel Clio had a DMF and both that and the DPF need doing €4000 would cover it but I reckon they'll be making more than €4000 when they are 4 years old, also were the diesels available for €9000?

r3nu4l

Here's some excellent DMF material from a guy who went all 'CSI' on his DMF after it failed

Link

shedweller

r3nu4l wrote: »

Here's some excellent DMF material from a guy who went all 'CSI' on his DMF after it failed

Link

Good link. I was going to post a video of a DMF animation but the first youtube link within your link already covers it. Being a maintenance fitter i can see how they are prone to failure. Are they all the same design?
http://www.google.ie/search?hl=en&biw=1280&bih=839&gbv=2&tbm=isch&sa=1&q=dual+mass+flywheel+designs&oq=dual+mass+flywheel+designs&aq=f&aqi=&aql=&gs_sm=e&gs_upl=1609l5365l0l18l16l0l0l0l12l325l3222l2.6.6.2
One quick google search later and i see that Renault even managed to squeeze gears into it, just to complicate matters more!:eek:

DoubleBogey

Recently went diesel myself. Was convinced on here to avoid it and stick to petrol but changed my mind in the end. I actually couldn't buy a petrol model of the car a wanted, it had to be ordered in with a 10-12 week lead time. Also spoke to a few people who hadn't got a clue what I was talking about. They've had care free diesel driving for years and like most people have never even heard of a DPF or DMF.

It goes without saying that the more parts something has the more chances there are ofvthings breaking.

shedweller

I think they are passive rather than switched on or off. The extra torque available in lower gears would deflect the springs more than in higher gears. Maybe this is why hard driving will wear them out over time?

DoubleBogey

DoubleBogey wrote: »

They've had care free diesel driving for years and like most people have never even heard of a DPF or DMF.

Are the diesels they have been driving for years equipped with a DPF?
Do they do lots of miles?

Antomus Prime

I drive a 02 Mondeo 2.0tddi. I mainly use it for commuting to and from work (very short trip, about 7km) and i find it grand on the short journeys... Although I was told by a mechanic frend of mine that I should be taking it out onto the m50 once a week and giving it a good blast to clear all the s**t out of the exhaust system.

The clutch and DMF went at about 120k miles and I got a new clutch and a solid flywheel supplied and fitted for €680, which i was told was a fantastic price!!

Personally I woulndt buy a petrol car again unless i got a savage pay rise!! lol

DoubleBogey

So what are the tell tale signs of a broken DMF? I've a 2 year guarantee so figure if nothing goes wrong in that period then my driving style is suited to the car. Otherwise I'll trade it for a petrol. Dont planning keeping it more than 4 years anyway.

DoubleBogey

DoubleBogey wrote: »

So what are the tell tale signs of a broken DMF?

Vibration, rattling or knocking.

When the DMF went in the Mondeo I had when the clutch pedal was to the floor I could feel the knocking through my foot and up my leg. If the DMF is goosed you'll know

Antomus Prime

RoverJames wrote: »

Vibration, rattling or knocking.

When the DMF went in the Mondeo I had when the clutch pedal was to the floor I could feel the knocking through my foot and up my leg. If the DMF is goosed you'll know

It was the exact same symptoms in my mondeo, and they werent gentle knocks!!