Clutch and flywheel

[lightning]

I believe that the Z3 3.0 is fitted with a dual mass flywheel.

What would be the symptoms of dual mass flywheel failure? I get a clattering noise when l stop the engine, but only if it is hot. It does not do it on start up.
I have been told this could be the DMF. Hopefully it is just the exhaust!

The car drives fine, although it's difficult to get smooth gear changes in the lower gears unless you are smooth with it. But l remember my friend's Mercedes C180 was the same, and that was new.

[Brian H]

Cannot comment on the DMF as I do not have a clue but in connection to your gear change symptoms you may benefit from bleeding you clutch line, when I did mine I also removed the clutch delay valve which gives you a better feel to the clutch.

[lightning]

Clutch delay valve?

What's that then

[BladeRunner919]

It's a valve that causes a restriction in the clutch line, so that when you raise the clutch quickly, the clutch is actually released more gently/slowly. It's probably to ensure that during fast gear changes the clutch (not a warranty item) takes the strain rather than the drivetrain (potentially a warranty item). The effect is that the clutch action feels a bit 'remote'.

[lightning]

I will try bleeding the system first, l bet it has never been done.

The delay valve is probably there to protect the dual mass flywheel. And yes you are right the clutch action does feel a bit "remote".

[Brian H]

Heres some pics of the CDV for reference: -

[Mac The Tank]

When the DMF went on my astravan, it was noisy as hell at idle but fine whilst driving. I believe it's to reduce the "rumble" you get with diesels and larger engines at idle.

Sent from my doohicky using whatsisapp

[Mike Fishwick]

Both the DMF and CDV are to protect the car from people who cannot change gear smoothly - mainly Americans! Neither are necessary, but have been forced on us, just like other useless items such as electronic throttle operation, cruise controls, oil level sensors, traction controls, ABS, brake pad sensors, and the plethora of pointless electronic gizmos which are now thought to be 'essential' on modern cars - particularly BMWs.

They are only necessary for people who never lift the bonnet, have no interest in their cars, and treat them like weapons. Do they need to be protected frm themselves? No - they should have been taught to drive with anticipation and cowardice! (Rant over)

Even in the UK a lot of people just dump the clutch, or force the engine to run at too low a speed in a high gear, as they lack mechanical sympathy, but even then it is difficult to damge a DMF, most of which are replaced with the clutch to save on possible future problems - or make extra money for the garage. The usual sign of a dead DMF if a lound rattle at lower rpm in high gears, when it will make a lound rattle of protest. For one to rattle as the engine is being stopped it would have to be in a really bad state, and would not just be obvious when the engine was hot.

Your hot engine rattle may be caused something as simple as a worn bearing in the belt tensioner pulley - try removing the belt - or if you have air con, first remove the air con belt - when the engine is hot, and then just start and stop to see if their is any difference. It would help if you had tried to see which end of the engine the noise is coming from, as we do not have crystal balls.

It is difficult to quantify a rattle via the internet, one man's rattle being another man's clanking.

[lightning]

Just a rattle when l turn off the engine.

Nothing on startup or when running. And only when the engine is hot.
It sounds like it is coming from the underneath of the car. I will investigate further.

[Mike Fishwick]

Somethnig else Iwould investigate is the viscous fan coupling, as - particularly if you do not have air con - it will be on the verge of engagement when the engine is hot, and it is possible that the steel plates may be able to rattle against each other when the speed falls below idle rpm.

It is easy to remove with a 32 mm spanner, and you could then decide if it is the cause of the noise.

It is always worthwhile checking for any play in the coupling bearing - even the slightest amount is a sign to replace it. Typical life is around 70,000 miles with air con (when most of the cooling work is performed by the electric condensor fan) and less for cars without a/c.

[lightning]

OK will do.

Can somebody tell me the procedure for bleeding the clutch hydraulics?
Does it share the master cylinder with the brakes, and where is the bleed nipple. Do l have to get underneath the car?

[Del]

Some gearboxes are also a bit noisier when very hot if filled with thin oil like ATF oil. BMW used to fill their manual gearboxes with ATF oil and some of the earliest Z3s may still have labels next to their oil filer plugs recommending ATF oil. Some car part sellers e.g. GSF, when they use their registration number based "prescription service" for parts and oil, still recommend ATF oil for some Z3 manual gearboxes. Is it possible that this was done by a previous owner?

The UK Castrol site is pretty good at recommending the correct oils.

[lightning]

Right, gearbox oil change on the "to do" list then