Now it's not often that Stone174 gets his fingers dirty and starts talking about things under the bonnet, but there's so much forum-talk, speculation, doom and gloom about the subject, I thought I'd do a little research and put something up on here.
Dual Mass Wha...?
The dual mass flywheel (or DMF if you like) is fitted in most modern diesel and petrol engines, both passenger car and light commercial vehicles. In fact nearly all Diesel Light Commercial Vehicles built today benefit from a DMF, providing van drivers with smoother more refined vehicles.
Engine torsional vibration (TV) has increased over the years due to greater cylinder pressure and increased compression ratios. These increases have been so great that a cure had to be found for the extra vibration. The DMF absorbs all the torsional vibration and gives the added benefits of reducing noise, reducing fuel consumption and protecting the driveline from the harmful vibration and occasional injector misfire.
Worried yet - what are the symptoms?
We first noticed ours going after the van had been stood for a couple of weeks; engage first gear from cold, pull away with a bit of gas and judder, judder, judder...
Once warmed up it all goes away. Using the van daily and it doesn't happen. Leave the van for a week and it's back.
Many people say there's nothing to worry about, it's just a build up of condensation on the flywheel, perfectly normal. I'd say ours has got noticeably worse over the past 12 months.
Time to replace?
There's never a good time I suppose, but there's always a bad one. More often than not we're in the van doing something we've been looking forward to; heading to a show, a week off work etc. The last place we want to be is on the hard-shoulder and making small-talk for several hours in the back of a recovery wagon (no offence to the AA). So, combined with a 90,000 mile service and MOT, we've chosen to replace the DMF and clutch in one go.
Is there a cheap option?
In a word, no. We're not ones for scrimping on pattern-parts, this is one item that needs to be OEM.
Parts required for the 2.5 174 engine will be:
Genuine LuK 240mm Dual Mass Flywheel
Genuine SACHS SRE Organic / Sintered Clutch Disc
Genuine SACHS SRE Pressure Plate
Genuine SACHS Releaser
Flywheel and Pressure Plate Bolts
This is an uprated direct replacement for the OE LUK Kit found on the 2.5 TDI Transporter T5 with the 6 Speed Gearbox. The Organic Clutch Disc are rated by Sachs to 390Ft/Lbs+
Parts cost is around £675. With roughly around 6 hours to fit.
What about going back to a Single Mass Flywheel?
Initially the unit cost may be lower, however in the long run damaging vibrations that were previously isolated by the DMF could affect or damage other parts of the vehicle. Failures can occur as a result of retro-fitting solid flywheels. Vibrations not eliminated by the flywheel have been known to destroy gearbox components, contribute to broken crankshafts and increase noise or resonance within the vehicle cabin to unacceptable levels.
So there you have it, not the sexiest of Christmas presents I've ever received; not quite the glamour of new alloys and airride of this time last year - but these part are just as important. The van is booked in to Aire Valley Workshop for the first Saturday in 2014 and they're keeping it for a week.
