Dual Mass Flywheels (DMF)

[Mat-Manchester]

Is this the sound of a mad midget trying to hammer his way out of hell????  (3 seconds in, ignore the rest). Only get this noise when pulling away the first few times on a cold day - garage diagnosed as "clutch related". 2010 Petrol, manual, VRS with the TSI engine, 58k.

 

https://vimeo.com/149035227

Edited 15 December, 2015 by Mat-Manchester

[ujtordai]

If you leave them too long they can catastrophically fail. We had one that locked the engine when it went, here are a few phone pictures:

 

How much was the mileage when this happen?

[AudiPhile300]

Hell,

I have a 2007 Octavia 2.0 PD BMM 4x4, thinking of replacing the DMF at some point, garage is indication fron subframe has to be removed/lowered to get the box out ??

Any advice on this, also, on my last Octavia 2.0 PD BKD, the garage that fitted the replacement DMF/clutch said there are special tools to set-up the DMF - but the garage quoting to do my 4x4 say we just bolt it on ??? wich is correct ?

 

thanks

[AVTUR]

The list that starts this thread suggests that Mk II Fabia diesels have a DMF, but a 2013 Monte Carlo 1.6 105ps diesel has a standard single plate, single flywheel clutch. My curiosity was piqued when I remember reading in the official brochure that the car had a single plate hydraulic clutch so I phoned my local dealer to confirm. Sure enough, when my car's details were entered into the data base it shows that it is indeed fitted with a bog standard single flywheel clutch. At least if the clutch does ever need replacing it's not going to cost me a vital organ!

[octyal]

Dragging this back up - but I thought that there was some extra info needed to be added. Even though I work for Schaeffler/LuK, some may say I am biased, but DMF's do good work, and only last year we made our 100 millionth DMF!

Anyway, some other things to consider when replacing/diagnosing DMF, and these are issues we see daily on the Tech hotline;

 

Injector balance - a sticky/blocked injector can lead to a loss of performance in one (or more) cylinders. This has the effect of unbalancing the engine rotation, leading to the DMF having to absorb more vibrations than it is designed for. Unfortunately, this is only discovered after the replacement has started rattling. It's something I tell anyone replacing a DMF on a diesel, have the injectors cleaned, or at least tested, while it's being replaced to avoid potential unnecessary warranty costs. This is especially important on PD engines, as the wrong oil can cause injector blocking, leading to this type of failure. An injector leak off test will confirm the condition, any more than 10% difference between cylinders needs to be investigated. More modern common rail engines can usually have the flow rates read via a good diagnostic machine (not sure if VCDS has this capability, but dealer level kit should), although the flow test will give a similar result.

EGR Systems/Throttle bodies/Air shut off flaps - Similar issues to the injector problem, although usually characterised by noises on startup or shutdown. A failed EGR (or non fully functioning one) will let unburnt oil vapours back into the inlet manifold. This coats components in thick sticky tar like substance, which can impeded the operation of and throttle flaps, or shut off valves. When shutting down the engine, the throttle body flap should close completely, if it doesn't, then the crank can "lurch" on it's final rotation due to excess air being drawn in. THis can cause the DMF to knock against it's stops, causing a noise. Replacing the DMF may alleviate the noise - for a short space of time - unfortunately, if the noise comes back, then it's usually too late.

FEAD (Front End Accessory Drive) - May seem unrelated, but they can cause issues. Seized OAP/OAD pulleys (alternator clutch pulleys) can allow vibrations to be transmitted via the belt to the crank. They may be minor, but can still have an effect on the DMF life span. At the same time the TVD (torsional vibration damper), which is basically a very simple DMF, can also cause problems. When they wear out, again vibrations from the FEAD can be passed straight to the crank and into the DMF. You can get a rough idea of the state of an OAP/OAD by watching the auxiliary belt. If the belt is flapping, or the tensioner is bouncing when the engine is revved, then you may want to consider replacing the pulley. In extreme cases, the seized pulley can cause breakage of the bracket that holds the tensioner. Again the PD engine is susceptible to this, as they usually break the little tensioner piston damper.

Poor Starting - If the car takes longer to start than it should normally, either down to battery condition, fuel system leaks, glow plug faults etc, then get the problem sorted. During normal operation, the DMF barely moves, but during start up and shutdown, it has to cope with both a sudden movement (starting) and a the sudden stop of the engine - this is where the most amount of movement occurs. Any excessive cranking (which is not exactly a smooth rotation of the crank due to the cylinder compressions) will lead to DMF wear.

Compression - Low compression on a cylinder(s) again can lead to imbalance in the crankshaft rotation, again giving excessive wear - similar issue to the injector problem.

 

There are more, lesser, problems that can affect DMF's, and as we find more, then I will add them onto the end of here.

 

On the question of DMF lifespan, well that's the old how long is a piece of string question. There is no set design life, and many factors can affect them (as have been already mentioned). We regularly get garages phoning up with DMF problems, on a car that has covered more than 150k miles on the original, only for the new one to become noisy after less than 20k miles. It's only when we point out the above, that they realise there could be other issues.

 

 

[octyal]

Hell,

I have a 2007 Octavia 2.0 PD BMM 4x4, thinking of replacing the DMF at some point, garage is indication fron subframe has to be removed/lowered to get the box out ??

Any advice on this, also, on my last Octavia 2.0 PD BKD, the garage that fitted the replacement DMF/clutch said there are special tools to set-up the DMF - but the garage quoting to do my 4x4 say we just bolt it on ??? wich is correct ?

 

thanks

 

Not sure on the subframe bit, but the DMF is a bolt on unit. They may be getting confused with the clutch which would require the self adjusting clutch tool to enable correct fitment.

[Arghhhhhelp]

On 05/05/2010 at 10:40, cheezemonkhai said:

This is started as a informational thread following comments in other threads and any posts with further information and/or corrections are more than welcome.

Please however don't use this thread to start a discussion on the benefits or otherwise of a DMF.

What is a DMF?

DMF stands for Dual Mass Flywheel.

A traditional flywheel is a large lump of metal, usually with a relatively high mass which acts to smooth out power and torque from the engine.

A DMF is made of two pieces of metal connected by a toothed and sprung system with damping.

A DMF is designed to reduce transmission gear rattle and ease gear changes.

Another function of the DMF is to provide isolation between the crankshaft and gearbox to reduce torsional spikes.

This is a useful web page, with information on DMFs:

http://www.cdxetextbook.com/trans/clutchMan/clutches/dualmassflywheels.html

This video on YouTube shows a DMF:

 

This video on YouTube shows a failed DMF:

 

What cars are fitted with a DMF

A DMF is fitted to the following:

Mk I Fabia:

- VRS (PD130)

- PD 100 models

MK II Fabia:

- TDI models

MK I Octavia:

- PD130 TDI models

- Some other TDI models. (1998 onward typically)

- 1.8T models, including vRS

MK II Octavia:

- All TDI Models

- 2.0 T and 1.8T petrol engined models.

MKI Superb:

- TDI models

MK II Superb:

- All TDI models

- Larger petrol engines.

(If you know others that are or that one of the above isn't post and I'll fix it )

Diagnostics

The following are signs that your cars DMF is possibly gone or on it's way out:

 

1. Your car "sounds like a mad midget trying to hammer his way out of hell".
2. Rough idle, combined with a jerky uptake of drive
3. Jerky pulling away
4. A large hole in your gearbox with oil pouring out.

 

Many garages will tell you that the gearbox has to come off to confirm if there is an issue with the DMF.

I've been reliably informed (thanks MoggyTech) that if you take the starter out, then you can see the play in a failed DMF.

Also my skoda dealer confirmed to me that there is an inspection hole on the 02m gearbox, which can be used to check the DMF.

It was suggested the price for either of the above routes was about the same.

This means a much smaller bill for diagnostics, so if your garage tells you they need to take the box off at hundreds of pounds to check the DMF, then you know it's time to find a new garage.

Likely costs to replace a DMF.

Typically if a DMF dies you should replace the DMF, new seals and the whole clutch kit at the same time.

The reason for this is that the labour cost for taking the gearbox off is a lot higher than materials and as such you don't want to have to risk pulling it off again.

Under warranty this may not be the case and it comes down to if the DMF has damaged the clutch.

Costs are around the £500 to £1000 mark, depending on who you use to carry out the work.

At present a DMF and clutch kit can cost from as little as £200 (none genuine) to about £600(OEM) although prices will obviously vary with time.

Likely causes of DMF failure and how to minimise the chance of failure.

There seems to be a good number of cases of premature DMF failure on cars reported on this forum and others.

While the DMF (or a certain design of DMF) may be a relative weak point in the drive train, there are some things can increase the likelihood of premature DMF failure.

 

• Racing Starts
• Driving around at very low RPM
• Putting a lot of power down from low revs
• Sharp and harsh application of the power
• Remap (See below)

 

All of these put much larger strain on the active parts of the DMF and can increase the likelihood of an early failure.

Avoiding these where possible and having some mechanical sympathy should reduce the likelihood of problems, but obviously the part is a mechanical items and will have a designed lifetime.

Regarding a remap, it should be noted that a remap can cause the car to deliver more power or torque than the DMF is rated for, which will obviously reduce it's effective life.

This is not a given for all remaps and it should be noted that the quality of a remap can vary wildly.

While some vendors will provide an excellent service, taking into account the DMF and other factors, there are others who may provide a poor quality map which takes no account of these factors and can shorten the life of the DMF and other components. (A search should reveal more).

Hope that helps.

I've a mk 1 fabia estate 1.9sdi what type of clutch is it I've been told its this type https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F332261397100

 

Any help I'd be very greatful

[cheezemonkhai]

I can’t help in your specific case other than to say that clutches change depending on the flywheel fitted.

[abaxas]

Random musing:

My old 8P 2.0 TDI A3 had a recall due to a dodgy batch of DMFs which somehow 'set fire to themselves'. I wonder if skoda cars of the same build era (late 2003) would/could have the same issue.

[AudiPhile300]

Remarkably, My 2007 Skoda Octavia II, 4x4 has now done 264,000 miles with no evidence of the DMF having been changed, I bought it 30 months ago with 205,000 on the clock, replaced a rear wheel bearing, front CV and boots, in process of fitting new rear shocks and springs, regular oil change and filter every 8-10K, fully synthetic, seems to have been worth the effort.  Bodywork not great (came originally from Scotland and has suffered for it) slight surface rust to cills.  Only expect it to last another 18 months so not unduly concerned, its a go anywhere vehicle, fields, tracks - only stuck twice  when bellied out in deep mud, very good traction.

Full dealer history, Haldex was serviced surprisingly - but they appeared to be oblivious to the filter, first job I tackled.  Propshaft centre bearing noisy at 2300- 2400rpm (known fault) I have another waiting to go on.  This model has a split propshaft that can be overhauled (if you can find the bearing) unlike the later models which are one piece and around £1600

[Adamos20]

Some of 1.6tdi skoda got solid flywheel from factory, my 2014 superb 1.6 tdi got no dualmass flywheel, its got solid flywheel. 

[Shaunieboy]

On 01/04/2019 at 20:29, Adamos20 said:

Some of 1.6tdi skoda got solid flywheel from factory, my 2014 superb 1.6 tdi got no dualmass flywheel, its got solid flywheel. 

Yup, my 2014 superb greenline 2 1.6 has a solid flywheel