Are DMFs in petrol cars just as unreliable?

Honest John Back Room » Motoring discussion
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Sun 11 Apr 2010 01:27
Are DMFs in petrol cars just as unreliable? - BackOfTheNet

Once again I'm thinking about changing my car.

I've spotted a manual C-Max 2.0 petrol with just under 50k on the clock which I rather like, but from what I've read on HJ's car-by-car breakdown, these engines are fitted with a DMF.

Does anybody know if these petrol engines more or less reliable than the diesels with a DMF fitted (not just the Ford diesels)? How do they compare in terms of reliability?

I haven't come across many tales of petrol engines failing due to DMF problems so I'd be interested in anyone's thoughts or experiences with petrol engines fitted with a DMF.

(Also, as an aside, do the Mazda 2.0 petrol engines have a DMF fitted? I wasn't sure if they were the same units as the tech spec and power outputs are different)

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Sun 11 Apr 2010 10:12
Are DMFs in petrol cars just as unreliable? - bimmer-driver

Far far more reliable in petrols than diesels. I've never sold one but sold hundreds of diesel ones.

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Sun 11 Apr 2010 10:18
Are DMFs in petrol cars just as unreliable? - corax

I shouldn't worry about buying a petrol car for that reason. A havn't heard of many petrol cars failing due to the DMF. I think you'll find many petrol cars are now fitted with one. The Haynes manual for my '98 BMW 323i says that it is fitted with a DMF.

Quite why a car with one of the smoothest straight six engines in the world needs one is beyond me, considering they were designed to reduce the vibration/harshness through the clutch pedal of a diesel engine, but thats progress I suppose. The clutch occasionally judders in damp weather, but I don't think its down to the DMF. Hopefully :-)

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Sun 11 Apr 2010 10:44
Are DMFs in petrol cars just as unreliable? - Alby Back

DMF equipped petrol cars may well be less prone to problems than diesel ones but it is worth mentioning that not all DMF equipped diesels will automatically fail. I've have done hundreds of thousands of miles in in DMF fitted diesel cars and never had a problem. They don't all go wrong by any means.

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Sun 11 Apr 2010 11:16
Are DMFs in petrol cars just as unreliable? - DP

My mk4 Golf GTI 1.8T has a DMF, and it's juddering like a good 'un on pull away, but it's done 130k on what we believe is the original clutch.

It just turns what would be a £100-odd parts job into a £300+-odd one. But at 130k, you can't really complain.

In any case, this will be converted to a single mass when the time comes so I never need think about it again :-)

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Sun 11 Apr 2010 14:43
Are DMFs in petrol cars just as unreliable? - nb857

My mk4 Golf GTI 1.8T has a DMF, and it's juddering like a good 'un on pull away, but it's done 130k on what we believe is the original clutch.

It just turns what would be a £100-odd parts job into a £300+-odd one. But at 130k, you can't really complain.

In any case, this will be converted to a single mass when the time comes so I never need think about it again :-)

I'd try bleeding the clutch first before you get too worried about the DMF. My car judders when the clutch need bleeding and shifts as smooth as silk after.

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Sun 11 Apr 2010 12:11
Are DMFs in petrol cars just as unreliable? - corax
I've have done hundreds of thousands of miles in a DMF fitted diesel cars and never had a problem.

I've said it before HB - buying a car previously owned by you would be like a one way ticket to trouble free automotive bliss! :-)

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Sun 11 Apr 2010 12:21
Are DMFs in petrol cars just as unreliable? - Sofa Spud

The dual-mass flywheel seems like a retrograde step. A single piece flywheel was about the last thing that was likely to fail on a car, unless perhaps a tooth got broken off the starter ring-gear. Isn't a DMF really just a glorified crankshaft damper?

Looking to the future, I'm also wondering how the Fiat Multi-Air pressure-hydraulic variable inlet-valves will fare as the engines age - but that's another story!

Edited by Sofa Spud on 11/04/2010 at 12:29

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Sun 11 Apr 2010 13:04
Are DMFs in petrol cars just as unreliable? - xtrailman

Its funny how any juddering on the clutch is placed at the DMF door. We had juddering clutches years ago with the solid flywheel. Too many assumptions are being made. I believe the real reason is the large torques produced by todays engines are the problem, along with under engineered parts

On my thired car with DMF, with no problems.

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Sun 11 Apr 2010 12:59
Are DMFs in petrol cars just as unreliable? - Alby Back

Not necessarily obviously Corax but I do fear that sometimes the tendencies of the few become believed as the norm for the many. When people encounter a problem, particularly a relatively expensive one, they perhaps quite understandably, shout about it. The ones who don't have problems tend to not mention it as they most likely hadn't even heard of the possibility. I know for sure that I'd never heard the term DMF until I started reading this site and I'd like to bet there are many drivers of said equipped cars who have no idea that they own such a thing or indeed what it is.

Human nature is such that bad news travels much faster and is delighted in much more than good and we all have to remind ourselves occasionally of how that can colour our beliefs.

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Sun 11 Apr 2010 15:19
Are DMFs in petrol cars just as unreliable? - corax

Only meant in jest HB, I would imagine that you have a fair bit of mechanical sympathy, coupled with the fact that you probably drive long distances and therefore the clutch/DMF gets a fairly easy life. I, like you, didn't even know that my car had a DMF, but I always treat the clutch gently as I know how costly relacement can be.

When you hear about DMF failures, it would be nice to see how those particular cars have been treated prior to failure. I know that on my regular commute to work, if I have the window wound down in the urban part of my journey, I can hear the sound of crunching gears and frenzied acceleration as people try to cut you up, I would have thought these cars are going to suffer from failures such as the DMF sooner rather than later.

But I would rather put up with a bit less refinement through the clutch pedal for something that I know is going to last. It comes down the difference between owning an older car long term or buying new, keeping for a few years, then changing again. Those people won't be worried because the repair would be under warranty. Although these things usually fail just outside the warranty...

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Sun 11 Apr 2010 15:33
Are DMFs in petrol cars just as unreliable? - markandchrissie

It's suggested that being "mechanically sympathetic" can reduce the likelihood of dmf problems, but my last van working for Royal Mail was a Transit Connect that had some serious abuse in the 3 years I used it. About 100 stop/starts a day, and regularly fully laden. After 40,000 miles when sold it was still on the original clutch (albeit on the end of its travel) and no problems with the dmf at all.

It seems to me every time you turn off a diesel engine it results in severe shock to the dmf as they always stop dead due to the high compression. Petrol engines are a lot kinder in that respect.

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Mon 12 Apr 2010 12:58
Are DMFs in petrol cars just as unreliable? - Mapmaker

So I guess that the clutch should be pushed out both when starting and stopping an engine with a DMF.

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