MY STORY. Dual Mass Flywheel Failure Symptoms. Solid Flywheel replacement ZD30 Y61 GU
Sharing my story which may helps others.
I have owned my 2001 GU Patrol ZD30tdi some 10 years, original clutch, lots of heavy towing. I was surprised my clutch was still going. One day over a month ago immediately on firing up the diesel, the engine felt as if it was about to jump out of the engine bay, a massive shaking followed by normal smooth idle. This happened every startup. I was certain an engine mount failure was the culprit but on inspection, the mounts appeared OK. A additional second symptom showed up a couple of weeks later. Once again, on every startup, the engine would want to jump out of the engine bay so it felt followed by rough idle. Out the exhaust pipe, it would sound like a cylinder was not firing. Surprisingly however, with a slight tap of the throttle, idle resumed to normal. Hmmm? Checked fuel filter and engine connections, checked most things and all appear well. Could it be an injector failing came to mind or worse, injector pump? As the week went by, the two symptoms remained but then a third symptom came into the picture. Driving in dead slow peak hour traffic at idle speed only, the engine went into bad idle mode, again as if on 3 cylinders. A slight raise of the revs and idle returned to normal? My clutch felt normal but did give a slight shudder each time the engine idle went rough so that brief shudder I put down to that rough idle. Oh yes, no engine error codes to look at, all clear since I replaced the TPS (throttle as in pedal position sensor)
Thinking collectively about the 3 symptoms, I started to wonder if I had a dual mass flywheel fitted that was failing and if that could possibly cause these symptoms? For all I knew, I may have had a solid flywheel fitted but I needed to remove the gearbox and all to see for myself, not keen on the job but mindful that I have been towing on and off for 10 years on the clutch and it must be near lifes end anyhow.
Firstly why did I suspect a dual mass (DM) flywheel being cause of my trucks symptoms? As a very simple analogy, just imagine the dual mass flywheel like this. You have a solid flywheel with ring gear attached on the outer. On the face of that flywheel, add another flywheel (minus ring gear). Join the two flywheels together with two springs in between each other so that when the main flywheel was rotating by the engine, the secondary flywheel will also turn being attached by the two springs. DM flywheels with springs were designed to dampen engine noise/vibration away from the gearbox in order to protect the gearbox, a visa versa effect too from my experience and also offer a smoother driver experience. However if you think about it, when the springs finally lose their "SPRING", the secondary flywheel can operate out of synch with the main flywheel under certain conditions, eg: at idle, the secondary flywheel can bounce or "shudder" back and forth independent from the main flywheel thus causing shudder, that is, rough engine idle symptom came to mind. A slight tap of the accelerator each time brought the two flywheels back into synch and ... no more bad idle. Interesting! But was this the problem with me? Only way to find out was to pull off the gearbox. The results were not surprising. I had a dual mass flywheel fitted. It had failed. Obvious was that two flywheels rotated independent of each some 10mm differential before one would connect to the other thus demonstrating to me that flywheel bounce at idle was likely. My bell housing was also coated with an 8mm thick bead of black burnt smelling 'SLIME' I will call it as I have read some DM flywheels have a central slime like ingredient sealed between them (perhaps like a viscous coupling, it offers traction to connect two devices at sudden load) which I guess was the case with me as there were no oil leaks from gearbox or rear engine seal. My old clutch pressure plate fingers were in good shape and still some meat left on the driven plate. Simply, Dual Mass Clutch failure was very evident.
Cutting it short, from a 7am start straight though to 2am next day be it a cold wet night during which time my wife came out a couple of times to make sure I was not pinned under the heavy gearbox/transfer case that I was raising, I had cleaned up the stinky mess, installed a new rear engine oil seal, a heavy duty solid mass flywheel kit of a reputable brand made for towing and had my truck up and running. Managing to squeeze in a much needed 4 hours of sleep was followed by a test drive and the results? No more rough engine idle, no more the engine wanting to jump out of the engine bay on startup. Next day, a 600km trip was made, the clutch felt great with the solid flywheel delivering a bit more feel through the pedal and shift stick on what was happening down below (just like the old days).
One other difference I noted with the solid flywheel was that at idle speed (750rpm), I could hear gearbox "chatter", a noise like two gears turning around together but by raising the idle from 750rpm to 850rpm that chatter sound goes away. The chatter noise to some may alarm them as "it was not there before then why now"? The chatter sound has always been there but was not audible when the DM flywheel was fitted. Simply, the DM flywheel would have dampened out gearbox chatter sounds, it was designed to do that, the solid flywheel does not offer that luxury if I can call it that, thus transmission sounds do get carried through the new solid fly wheel install. But, up the idle a bit, and the sound will go almost if not all away, it does for me. For some owners, the gearbox chatter sound will be annoying and may result in disappointment but taking into account that a DM Flywheel kit at 'supply only price' was to cost me $3,400.00, my heavy duty solid mass flywheel kit was a third of that price and together with longevity compared to a DM flywheel, my install ticks the boxes for me. A long story yes with apologies but the detail is important and may help others.
Cheers to all. Ed
Over 40 years experience restoring cars from mechanical, bodywork/spray painting and motor trimming.
"One never stops learning about cars".
