[vliegwielolaf1234]

Can the <acronym title='dual mass flywheel'>DMF</acronym> cause a light shake/vibration .

At idle and around 2200/2300 rpm , and this is only standing still car not in gear . so free reving the engine

There is no shake during driving or any other clutch noise or problems ,

I did change the clutch about 20k ago but not the <acronym title='dual mass flywheel'>DMF</acronym> , and there was some play i guess around 2 cm .

I am thinking my flywheel is getting to the end of it's life ?

Could it cause a unbalance or shake/vibration ?

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[Scott Collins]

Mine did this at around 75k miles - mostly at idle. A bad motor mount can give you a similar unwanted vibration. My motor mounts had recently been replaced so we ruled that out. Anyhow, RS Barn replaced the <acronym title='dual mass flywheel'>DMF</acronym> and showed me the problem after the old <acronym title='dual mass flywheel'>DMF</acronym> was on the bench. If my memory serves me correctly, there is a rubber plate between the two flywheel surfaces, sort of like an Oreo cookie, for dampening I suppose. This had degraded and become loose, which caused the vibration. On the bench, you could see the effect by pulling on the flywheel unit in opposite directions. From his experience, Pete could tell how much play was acceptable and how much was not. Mine was in the "not acceptable" category. Once replaced, the idle was back to smooth and the problem was solved. If I had not addressed the issue, the flywheel would have continued to become worse and eventually hurt my feelings, if you know what I mean.



So, I would first check the motor mounts, which can also degrade and loose the fluid inside. If that's not it, then you might go to the flywheel.



If Pete, from RS Barn, reads this, he will probably chime in.



-Scott

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[flash]

the 2 concentric masses of the DMF rotate relative to each other. the should rotate about 2", but return back to their originating position fairly quickly. when it is slow or does not return, you know it's toast.



the motor mounts are to be changed at 63mm measured flange to flange and will make contact at 62mm. new is 70mm.

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[vliegwielolaf1234]

I think i am in for a flywheel .

Motormounts could be , i need to check them and get measurements , but since it's more like a shake kind of thing it feels like something heavy is doing it also the higher rev shake would indicate more towards the flywheel .

allready asked a friend to see what price it would be at the dealer , he get's a discount there <img src="/forum/images/smilies/968/clap.gif" class="smilie" alt="" />

Really intrested in RS Barn Pete his opinion .



Thanks

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[MB968]

Has anyone ever taken a <acronym title='dual mass flywheel'>DMF</acronym> apart to see how they are assembled. I've designed a lot of tuned mass dampers for similar, but different applications. I'd like to get my hands on one to look at. Sounds like it's just a typical sandwich of viscoelastic element (there are a lot of polyvinyl cloride mixes, butyl rubber, etc. choices) between two masses. We'd just have to match stiffness properties at operating temperature, and get a reasonable match for loss modulus. If it was cheap to replace a <acronym title='dual mass flywheel'>DMF</acronym> it wouldn't be worth the effort, but at their high cost might be worth taking a look at.

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[flash]

i haven't taken one apart, but as i remember, it doesn't come apart, and there is a spring in there



i think i still have a dead one around here somewhere from the clutch disk project. i'll look at it.

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[vliegwielolaf1234]

The shake is more pronounced when the car is fully warmed up 30milles + .

That would make sense since the rubber would become more flexible when warmed up .

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[MB968]

It looks like a series of parallel rods that might be pressed in are used to tie the two weights together. Looks like you might have to put one up on a mill and mill out the swaged end of the rods, or it might be as simple as pressing them out(can't tell if the one end is just a straight diameter or not.

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[tamathumper]

In a related turn of events, now that I have the lift working I've taken out the clutch and flywheel to replace them. I have a "buzz" at 3300-4400 rpms that just bothers me, and the mechanic said he feels it's a <acronym title='dual mass flywheel'>DMF</acronym> issue and that my "wear measurement" was out of spec - all at 40K miles?



So, I've purchased another clutch and flywheel, but now that I look at them, side by side, the wear surfaces are virtually identical... The clutch plate is the same thickness, the metal surfaces are the same thickness, etc... Albeit there's some waviness to the old ones and the replacements are nice and flat, but other than that they are the same thickness so how could my "wear measurement" be any different?



My question is - how DO you test that <acronym title='dual mass flywheel'>DMF</acronym> when it's out of the car to tell if it was causing any kind of problem?



And while I'm at it, how thick is that clutch disc supposed to be, anyway?

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[flash]

did you just get your belts done?

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[MB968]

I know I've seen it before, but can't find it now. Where can I find the wear measurement spec.

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[tamathumper]

Belts done and redone three times. Shop swears the timing is correct. I was waiting for the belt DIY to check it myself, but figured this was quicker.

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[vliegwielolaf1234]

I do not see the <acronym title='dual mass flywheel'>DMF</acronym> making a buzz , on the other hand throw-out bearring could if bad or not correctly installed.



Could you be more specific about the noise ? In gear / free reving ? .

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[flash]

at that rpm, it is usually the lower balance shaft being off by 180 degrees.



this happens WAY TOO OFTEN. the problem is that the lower shaft drops down if you let go of it. the keyways are both supposed to point up, but you put the gear on differently so the notches line up the way they need to.



i went through this 3 times with one shop too. but, they kept looking at the marks and not the keyways, so it was wrong all 3 times. it wasn't until i made them actually take it apart, and most importantly remove the big washer covering the front of the gear, that they could see the keyway and verify that it was off.



when the DMF goes, it vibrates all the time, but more at idle

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[tamathumper]

This is more of a harsh buzz, which I think is getting worse and across a broader RPM band. If I accelerate hard, it doesn't happen. When I got the car, it was smooth as silk all the way through the RPM range. Then I had the belts done, and it had a buzz at 4400 rpms. Now, it's more like 3300 to 4400, and annoying me. If someone were to borrow my car, I doubt they'd even know it was there.



The belts were done about 2400 miles ago, so I wonder if it's getting worse because it's due to be retensioned? The shop owner told me the belts were "off a tooth" the first time I took it back to him and complained about the buzzing. After the third trip, he put a monkey wrench on the driveline in the rear and moved it back and forth, saying the little "clunk" that could be heard up in the bell housing was a sign of a bad <acronym title='dual mass flywheel'>DMF</acronym>. Having taken it apart, I can't hardly move the two components relative to one another by hand, and I can't tell it apart from the replacement as far as motion goes.



There was a discussion about this coincidentally when the shop was first doing the work, and I took it in and made the guy take it apart again (supposedly he did) and he re-verified it and said he took off the washer and used the keyways and everything, but I can't verify that he did all of that not having seen him do it. I do have his elbow divots in my fenders to prove he did *something*, but he might have been leaning over the fenders drinking a beer for all I know...



The <acronym title='dual mass flywheel'>DMF</acronym> seems fine to me - it doesn't move freely (neither the old one or the replacement).



There are some curious furrows on the release bearing fork cross pin (951-116-133-00), where on one half of the shaft the needle bearings wore themselves into the metal. Looks like I'll be replacing that anyway along with new bearings.



So, belts will be verified later and that will be a different thread. My question remains - how DO you test that <acronym title='dual mass flywheel'>DMF</acronym> when it's out of the car to tell if it was causing any kind of problem? And while I'm at it, how thick is that clutch disc supposed to be, anyway? I can't see the possibly 1mm difference between these two clutch discs making up for the 10mm of travel in the "wear adjustment" in the shop manual.

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[flash]

just left you a message - ring me up

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[tamathumper]

Neither <acronym title='dual mass flywheel'>DMF</acronym> can be rotated by hand when on the bench, other than a few centimeters as measured along the outside circumference. The old <acronym title='dual mass flywheel'>DMF</acronym> and pressure plate are "wavy", I don't know what "scored" means, but they are not smooth. The replacements are, at least, very smooth. The clutch disc on the old one is 7.1mm and the replacement is about 7.8mm. The surfaces on the new ones are dirty, but should clean up nicely.



Here's a picture of the scoring on the throwout cross shaft, just on one half of the circumference. A new one has been ordered.







And here is a pic of the old, and new pressure plate(s). You can see the waviness in the old one, whereas the new one is very smooth.

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[tamathumper]

At some point in the past 20 years, an enterprising chipmunk somehow got an acorn behind the flywheel - bully! The mainseal looks dry, and I'm not inclined to mess with it if it's OK, I've heard horror stories about getting that thing out and replaced without scoring the surfaces...



Recommendations - do it anyway you sissy, or let sleeping seals lie?







My hesitation is that I had zero oil leaks until I took it into the shop and had them replace the seals, just because they were in there doing the belts and rollers. Now I have little drips everywhere and the smell of burning oil for the first five miles when I drive the car (while stopped).







My remaining question is - how DO you test that <acronym title='dual mass flywheel'>DMF</acronym> when it's out of the car to tell if it was causing any kind of problem?

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[MB968]

I know many may not agree with this, but I would leave the rear seal alone.

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[flash]

the DMF test is a rotational resistance and rebound test. you have to have one mass locked down, and then rotate the other relative to that one. this will require some force. the masses should rotate relative to each other at least an inch, and then rebound smoothly and evenly back to the starting position. it won't snap back, but it should be fairly brief

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