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I recently bought a 03 plate Golf TDI Match from the local car auction . Ex lease car 70,000 miles great condition , full service etc. After a few days use we noticed the clutch was dragging making gear selection a little stiff and reverse was a definate crunch. Looking at the service history it had a new clutch fitted 6 months previous. Having contacted the local VW dealer they said take the car in it may be covered under warranty. The car was booked in clutch stripped. Phone call "Needs a flywheel sir, and clutch, all in £760" . Because its the flywheel no warranty cover. Has anyone else been suckered in by the main agent before. After all a clutch only lasting 6 months and less than 10,000 miles. The mechanic said they always fit a new flywheel with a new cluth -Dual Mass- £380, ouch. I used to be in the car game and have changed many clutches but never a flywheel, a new way to get money from customers i think. Wont entertain the VW franchises again.
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Flycog
Only a very brave idiot fits a new clutch to what will be a very tired DMF. It's a near-certain way to make them fail.
There's nothing new about them; they turn up, mainly on diesels, right back to K-plate on things like Toyotas.
That price for new DMF and clutch is quite good; a 52-plate Shogun Di-D broke one up recently at 30k and that went over £2750.
Now you know why it was sent down to the block....
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Screwloose i'm sitting here looking an even bigger open mouthed idiot than usual, did you put the decimal point in wrong place.
Surely that must have been including resulting damage to Gearbox/bellhousing crank....something?
I have to confess to not having a clue what is the difference between a dual mass and a normal (we've been using them for donkeys, if it aint broke don't fix it ) flywheel? And why/what benefit?
Jolly glad were now down to 2 cars and theyre both proper auto's.
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gordonbennet
Nope; no damage, just a knock - knock when you blipped it. The dealers have sold dozens.
The DMF on it's own was about £1500; add a genuine clutch and all the trimmings to about 7 hours labour and, with the VAT, there you are.
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Strewth and ninepence Screwloose I always understood mitsi knew how to charge well but thats incredible. Trouble is no GSF or europarts for these boys so youre stuck.
Well flycog sounds like youre getting a bargain,
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Gordon bennet & flycog obviously haven't experienced the joy's of modern motoring. The VW golf scenario is a common one & DMF's do fail. You could of had just a clutch & then paid to have it all done again a few months later.
Diesel cars now need their clutches treating with a lot of respect due to the torque the engines produce. Go easy on them chaps!
Doc
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Valeo are now doing solid flywheel repacements for Golf IV
see tinyurl.com/234gpv
Just hoping that they produce a kit for the HDi picasso before I need one! Supposedly in developement - but has been for over a year.
There appears to be market in the states for solid replacements.
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pmh (was peter)
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pmh
There have been reports of problems with solid flywheel kits. These engines have had their harmonics tuned to use a DMF - without one, there have been unwanted side-effects like cam-belts fretting and failing from "crank chatter."
[A useful phrase, that one...]
It looks like we're stuck with the flimsy things. As it stands; any garage that changes a clutch and doesn't replace the DMF with another one will be held liable for any consequential damage. So why should they take the risk, [and loss of 10% profit on the DMF] just to save the customer money?
Another good reason never to buy a diesel out of warranty. Diesel really is over.
Edited by Screwloose on 20/10/2007 at 13:30
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>>These engines have had their harmonics tuned to use a DMF
How do the solid flywheels compare in size with the DMFs?
If they are the same outside dimensions, but solid, then the crank will see much more inertia on its tail end, and this will bring down the resonant frequency, perhaps to a point in the range were the engine spends more of its time.
If I were looking at this, before I had completed the hard sums I would doubtless enjoy doing, I would imagine that an appropriate replacement solid flywheel would have comparable inertia to the crank side mass of the DMF.
Number_Cruncher
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NC
I've never had the time to assess the relative fixed masses of the two types. Visually; the solid flywheel is much thinner and uses a different style of pressure plate to compensate.
If that is the case and only the crank-side mas is equivalated; then there must be a noticable increase in rotational speed/cycle variation. There must come a point with some high specific output diesels that only a DMF can cope.
As we're now seeing 170PS four-cylinder units [in my youth that was full-race tune - on a petrol! What was the first BDA's output?] the acceleration/deceleration forces per cycle must be impressive. It would need a very unwelcome solid flywheel mass to smooth that sort of variation.
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Gordon bennet & flycog obviously haven't experienced the joy's of modern motoring.
IJ from the sounds of it will be some time possibly never that i experience the joys of a modern manual, in my job i deliver hundreds of new cars/vans and 4x4's and i find that only the vans (generally with one or two exceptions) have the low revved torque to be acceptable for me to have as a manual.
I drive the old way with as low revs as poss all the time incl take off, this isn't to say i'm slow on the road, its just i hate having to thrash a vehicle to get it to go, and i can assure you loading some modern td's i find them absolutely useless below 2000 rpm so how you can expect good clutch life when you have to thrash the living daylights out of a motor just to get the thing moving beats me.
The manufacturers can do it my new toyo is on maximum torque from 1400 rpm but i still plumped for the auto (just lazy now i may one day totalise my driven mileage and die of boredom in the process) so they can do it.
No one has explained yet why this dual mass flywheel is the new must have, how come we managed for years with heaven forbid ordinary flywheels, i have driven trucks for some 30+ years and some of the older engines (the ones we made) were very powerful unlike the latest offerings from elsewhere and i don't remember the massive costs of having to replace flywheels at clutch change time
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I agree the modern derv engine are much like petrol power today. The first diesels i owned were 1.6 cavaliers and escorts, slow yes but could pull away with next to no revs. These engines ran and ran, no MAF to fail no engine managment light to flash up at £60 a time to talk to it. These cars were cheap to run and maintain and not purchased as a performance car. As long as the cambelt , oil and filters changed at service they never ever missed a beat. The last great diesel engine for DIY maintenance and reliability was the PUG xud 1.9 of the late 90's, still in use on some cars now but stiffled with emmission gear. As others have said the modern diesel car is a liability when out of warranty.
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No one has explained yet why this dual mass flywheel is the new must have how come we managed for years with heaven forbid ordinary flywheels
It's the high power output of small engines; e.g. 170PS from 2.0 litres. As the crank turns every piston has to compress a huge amount of air forced in by high turbo pressure - which slow it's rotation speed markedly - and then it's spun forwards by a massive surge from the combustion of that charge.
This rapid slowing and acceleration of the crank's rotation causes an engine to rock on it's mounts and would vibrate the whole car unless you smoothed it with a very heavy flywheel.
The two-part DMF allows the crank to move independently of the clutch and smooths out the pulses that way for much less weight - while it lasts....
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sq
Thanks for the explanation Screwloose, and i understand what you are saying but cannot understand why not just a heavier flywheel without making it so damned expensive and complicated, we have had heavy flywheels since steam days.
I have the sneaky suspicion its like many new ideas once one starts the others have to follow the new craze bit like lemmings and we all know what happened to them.
Got a feeling Flycog you and i were much happier with the old mechanically pumped indirect diesels...bet were not alone
Edited by Pugugly {P} on 21/10/2007 at 23:13
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>>but cannot understand why not just a heavier flywheel
It's the two mass bit that's important. The springing between the two parts of the flywheel effectively isolates the transmission from the torsional oscillations of the crank which Screwloose has described. The main function of the DMF is to improve noise vibration and harshness. You could say that it's one of the additional parts which has made modern diesels more acceptable in terms of refinement to people who were used to petrols.
One of the problems of engine design, particularly diesel engine design is dealing with the torsional oscillations of the crank. These vibrations can actually build up in magnitude and twist the crank so far that the stress produced by the vibration is actually damaging to the crank. Left completely unchecked, a snapped crank is the likely outcome. Typically, the stress would be highest at the change in section at the edge of the main bearings, and if there's poor detail geometry, and/or poor (tensile) residual stress in the crank surface, then it's likely that a fatigue crack will initiate there, and then grow a little during each vibration cycle until the crank snaps. Great fun!
Via the DMF, the crank will "see" an effective mass, and an effective stiffness looking into the transmission. If you do away with the DMF, the mass and stiffness which the crank drives will change, and the way the crank vibrates will change. Someone somewhere should have done some sums to make sure that the solid flywheels will not upset the dynamics too much - it seems that these sums either haven't been done, or have been done badly.
Number_Cruncher
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NC
Like so many other cheap fixes; NVH comes a long way behind LSD.
Steve Cresswell - VW guru extraordinaire - says that a solid flywheel on a VAG TDi makes the engine feel "horrible."
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Thankyou for the explanations i am now even more happy to continue with proper auto's for the future, no doubt you can now shatter my calm by telling me tales of woe with these.
Don't suppose they could have used a balance shaft instead?
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>>Don't suppose they could have used a balance shaft instead?
Not really - balancer shafts are used to counteract unbalanced forces and moments of the reciprocating parts of the engine. They reduce the amount of bouncing and twisting of the engine (twisting at right angles to the crank; i.e. crank nose up, flywheel end down, etc, as opposed to twisting along the axis of the crank.).
The DMF is reducing the variations in torque and twisting that are passed from the crank into the driveline - i.e., twisting that is lined up with the crank axis. This twisting is both passed into the driveline, and is also reacted via the engine mountings, and hence felt in the car via two routes.
Number_Cruncher
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