DUAL MASS FLYWHEEL
The dual mass flywheels fitted to 1.9 and 2.0 tdi engines are very similar.
They are either made by LUK or Sachs.
It doesn’t matter which make you fit, just don’t mix and match parts.
Why fit a dual mass flywheel.
There are a number of reasons for fitting dual mass flywheels to engines.
The main ones are:
1. The ability to smooth out engine cylinder pulses at low revs which allows idle speeds to be lower and improve economy slightly.
2. The ability to smooth clutch bite so allowing for a smoother gear change.
The dual mass flywheel adds very little to the manufacturing cost of a car but adds a significant future repair cost for the owner.
A future clutch change is likely to require a dual mass flywheel change as well. This roughly doubles the cost of replacing a clutch assembly.
How the dual mass flywheel works
The BLACK circle with two pegs marked A and B is on the rear of the front plate so can’t be seen.
The YELLOW marks are TWO long compression springs.
Which ever way the front plate tries to turn, it must compress a spring first.
SO…when the clutch is lifted the friction plate grips the dual mass flywheel front face. With a normal flywheel, this would result in the clutch spinning with the flywheel almost instantly.
With the dual mass flywheel, the springs between the front plate and back plate have to be compressed before the clutch starts spinning. This compression of the springs acts like a shock absorber and makes the “clutch bite” feel softer.
The picture below shows a clutch friction disc, pressure plate and dual mass flywheel removed from a Passat B6 1.9 pd after 115,000 miles.
The car lost drive when the clutch failed.
The friction plate has lost its friction material. You can see the rivets that held the friction material on and the remains of the material can be seen mostly as black dust and fibres.
The pressure plate was still ok as a pressure plate but has a deep score running round it where it has been cut by the friction plate rivets.
The dual mass flywheel face is ok because the friction plate material for that side was still intact.
The dual mass flywheel has seized, slightly twisted clockwise. This made it more difficult to get the six fixing bolts out.
If it twists and seizes further round, it becomes impossible to remove the fixing bolts.
How do you know if the dual mass flywheel is failing.
It will make a chattering noise a bit like having two diesel engines running at the same time. This may develop into a knocking noise.
A failing dual mass flywheel will also make the clutch feel odd as if it has a double bite. It bites once as the friction material engages and a second time when the flywheel twists. You can’t feel the twist with a new flywheel.
Can I change the dual mass flywheel my self.
If you can change a clutch, you can change a dual mass flywheel. In some respects it is easier.
When you buy a dual mass flywheel/clutch kit from Sachs or LUK it comes as a ready assembled unit, complete with new bolts. All you have to do is unbolt the old one and bolt on the new one.
You don’t even need to align the clutch as it is already set on the flywheel.
You do, of course, have to take the gearbox off to get to the dual mass flywheel and clutch assembly.