[Valkman]

First timer here on the forum. Anyway, I also suffer from the annoying vibration, most significant around 2k and 3k rpm. I haven't got any codes related to misfires or anything else and my friends seems to ask is this running on all cylinders while reving the engine standing still. I've already done something to find the culprit.

I've replaced my flywheel and clutch assembly, had my exhaust system disconnected from the chassis during engine running (except from the manifolds) and the fan (viscous coupling) disconnected. It feels like something is out of balance. No popping from the exhaust, so I trust no misfires either.

I know my viscous coupling bearing has play, the water pump axle has play and one of my belt pulleys creates a noise at cold ambient temperatures. No other problems whatsoever. Vanos solenoids are replaced about a year ago along with the MAFs.

I'm thinking next about checking the harmonic damper, maybe running my engine shortly without the belt also. I really can't find any other reason for the vibration, since my flywheel (one of the heaviest parts) is replaced. Also no codes. Play in connecting rod bearings seems a bit far fetched, since so many other suffer from the same symptoms.

But before that, a full body paint job has to be completed

 

[Valkman]

no, no check engine light. this isnt a misfire etc problem.

andy-you had this issue on an m5 or some other car? i actually checked the pulley and i dont see it wobbeling etc when the engine is running.

Nightkrawler, good thing I'm responsible just for the flywheel change that I did myself and with a new flywheel costing 30% of a new one

The thing that made me think the flywheel was shot, came from the assumption that while reving the engine with a "snap" (blip the throttle) you could hear a metallic sound like something was hitting its limit. Flywheel was the first thing on my mind of course. But the vibration damper could make a similar noise. I've seen vibration dampers that make a horrible noise (in a five cylinder diesel engine for example) and the generator, two pulleys, water pump, power steering pump and the vacuum pump was replaced before they took the vibration damper out and with a long heavy screwdriver tried to spin it while attached to a vise. Only then I could see it move (obviously took a great deal of effort). It just wasn't attached in the outer edge. And no visual evidence of the vibration damper being shot before that.

 

[Valkman]

so what are you saying, your crank pulley(damper) was shot? i though you said you still have the vibration? did you put in a new flywheel or used, stock dual mass or after market?

Yes I do have vibrations. I was just telling an example of a damper case, where it was impossible to make any assumptions before the damper itself was on the table.

The flywheel was new as told earlier, stock dual mass. The old and new one felt similar and I suspect a worn/bad flywheel would indicate other symptoms also.

I'll be checking the damper later on.. still have the paint job undone. After that, might be taking the vanos apart myself and sending them to be fixed to the Dr. himself :biggrinbounce:

 

[Valkman]

Rotating parts during idle in neutral and clutch pedal up are crankshaft along with flywheel, clutch assembly, clutch disc and both axles in the gear box (no power out from the box though)

Clutch pedal down same parts are rotating except the gear box axles and clutch disc is now at standstill.

I haven't had time to manage this problem but I still stand by my words, it doesn't have to do anything with the flywheel, clutch or exhaust unless you suffer from other symptoms (like vibration during clutch drag etc.)

Nightkrawler, have you done the throttle sync yet?

 

[Valkman]

Yes, unfortunately I still have it. I've been really busy with the paint job and are going to finish the assembly sometimes next week. Damn that blue looks good fresh mmmmmm

Anyway, will be taking this issue next on my list. Good thing you took a look at the butterflies. I would consider the measurement of yours pretty accurate and on the other hand this problem would exist only during small throttle openings if the sync would be lost. At least I'm suffering from the vibration no matter how much you push the pedal.

 

[Valkman]

yesterday i replaced the motor mounts. the vibration is still there but i'd say it has been reduced by 30% or so. im starting to think it is not related to the flywheel, but something with the engine. m5 engine mounts are indeed fluid filled. i drilled a hole in one to see and sure enough fluid poured out.

Did the mounts look to be more compressed compared to the new ones? I mean did they seem to be shot by eye?

You seem to have mechanical skills but have you checked your vibration damper? It means you have to remove the belt wheel at the crank to see anything...

 

[Valkman]

Hopefully your problem haven't got anything to do with mine... I could've sworn that my flywheel was shot, but still renewing the wheel with a new OEM flywheel the vibration was still there... not even a slightest change.

 

[Valkman]

valkman, so you are saying you had the same vibration. installed a new oem flywheel and it made no difference? if so wtf else could it be?? this dosent make any sense.

Did the customer report anything about the vibration?

Yes, I have a vibration occuring exactly at about 3100 rpm or something like that. Another one is somewhere over 2000 rpm. At 3300 rpm the vibration is COMPLETELY gone. I changed the flywheel and it did absolutely no good. After that I disconnected the exhaust pipe from the gearbox, driveshaft tunnel and from the mufflers and it still did the same vibration... the whole exhaust disconnected (except from the headers)

 

[Valkman]

valkman, did you change the flywheel bearing also?

If you mean the ball bearing at the crankshaft end, answer is no. Actually I thought about it, but after feeling the bearing spin freely without any play, I didn't think it was necessary.

watchme's comment about the damper is really interesting. I've thought about it over and over and know the construction of the damper and how it can look fine, but still be bad. I haven't yet took my into closer look, but might do that soon.

 

[Valkman]

Interesting comments starts to arise.

I've got a friend selling measuring devices and planning structural measurements including vibrations, forces, bending and things like that. He's got almost 30 years of experience in that field so I might be asking him for some advice or even get him to measure the accurate frequency of the vibration. This would clearly help us find the possible culprit.

Just out of curiosity... I managed to get the vibration stronger when accelerating and turning right in a long high speed curve, as a highway ramp or similar. This would indicate something that's transmitting the vibration to "lean" more stronger against the body... exhaust, transmission or engine for example... meaning the source is dampened by something elastic.... I'm confused and at the same time surprised, that bmw isn't aware of anything like this.

 

[Valkman]

i've changed the motor mounts,tranny mounts, and the two exhaust mounts over the rear support bar... no change. i doubt it would be rod bearings as 40k is really low mileage for them to fail. the one at work had 38k the other 100k, i doubt bad rod bearings would make it that far. the 100k one has probably had this vibration for over 60k if not more miles and seemingly has not caused any harm.

im going to remove the vibration damper this weekend and inspect it. i was thinking of removing it and running the engine but i dont know if it is a good idea to run it the damper on. anyone know?

I've heard bad rod bearings and can't imagine how they could come with vibrations occuring at specific areas without making any serious noise. I've listened to my engine oil pan while another one was holding the revs and I simply couldn't hear anything.

I'm not sure if removing the damper and starting the engine is a good idea, but most likely won't harm anything during the testing. I guess the main reason for the damper is the belt drive and it's protection from the uneven engine cycles (which is natural on every otto engine). But the visual check on it would be great, since I guess just a few really have changed these..

Apeman, I know that curve and haven't tried on that one, but the vibration is stronger in curves (even if not in the 3k area) and vanishes almost completely when coming out of the curve into the straight... Although the specific areas are always there...

 

[Valkman]

i actually have thought of this but to check them the tranny has to come out so might as well just replace it.

And if it's worth anything, I torqued the bolts myself, when replacing the flywheel... according to TIS of course.

 

[Valkman]

And I could bet it hasn't got to do anything with the injection/ignition systems... that's because I can drive the car with a low gear on the highway up to say 4000 rpm and let of the gas. During fuel cut I still can follow the rpm needle lower slowly and feel the vibes happening at the exact rpms.

I drove my car on a lift at work yesterday and had a mechanic friend feel the car underneath. Even if I felt the vibes myself, he didn't see anything moving around or acting crazy... even by touching parts by hand he couldn't feel it... This vibe is really something you have to be aware of, before knowing about it.

 

[Valkman]

Just makes me think why of why I didn't go with a aftermarket solid flywheel :sad1:

I dunno, this confuses me .. seems a lot of people have it and nightkrawler had two cars in a row at his workplace so it just makes me think BMW just have made a design flaw... a flaw that for some ridicilous reason is magnified after certain parts being worn out. I guess we would have to bolt a calculated huge mass somewhere in the body and let it take all the vibes

I don't know about others but it bothers me why the exhaust tone of my car during the vibration sounds like a car with timing slightly off the normal (okay, it has a Vanos). The exhaust is kind of loud and has a drone... not from misfires, rather just from the timing change. I haven't heard many M5's other than just passing by, but a sound like this would've catched my attention. And a comment from my collague was that "is this thing running correctly... it doesn't sound right".

 

[Valkman]

I would've wanted to test a solid one for the purpose of it's lightness and even for the natural frequency change it's going to do. Although I've heard it causing more rattle from the transmission... maybe I'll take the vibe instead...

 

[Valkman]

Well, I have to say I am ecstatic! Today I just brought the beast home from the dealer...with no vibration! I have Tubi's on and I was told by the original owner that the vibration was related to the exhaust. The dealer took off the aftermarket urethane trans mounts and replaced them with stock BMW factory mounts...problem gone! I have to say I can't believe how smooth it is. I have always heard the difference in the tone of the exhaust as well...or at least I thought I could. After almost two years of ownership I have a new heightened appreciation for my beast. Hope this helps some of you.

Would you consider your vibrations similar to ours? That is, worst at 3200-3300 rpm?

 

[Valkman]

I did some vibration measurments last night over the gearbox and at idle. The idle speed is 960rpm/16hz. Its a very high idle, think I have some problem with the oil seperator lines.

Anyway, I got 3,2 mm/s RMS on the flange between the engine and transmission, vertical direction and 3,1 mm/s RMS horizontal direction. On the rear end if the transmission I got 2,7 mm/s rms on both vertical and horizontal (there is no rotating on out going parts here anyway since the shifter is in neutral)

The components that are the cause of the vibration on the front of the transmission is not a 1xRPM but a 2,66xRPM component. This means that I can rule out unbalance in the flywheel for now since a unbalance will only occure once every rotation, or 1xRPM. We can see a sligthly component at 1xRPM but this is normal on rotation parts. The value are not high.

I will try and take some vibration measurments while driving the car.

You being with no exception a professional in this field, would you consider looking from these results that we're talking about a mass that's spinning? How about if a vibration damper that's bounching back and forth while spinning (from a small play), could it cause this?

Would there be any help, if you measure the body itself? Because clearly the vibration is felt there.

 

[Valkman]

Vibration damper... that's what I'm thinking right now... but who knows... (devil knows)

So I called my friend, who's an expert in NVH- field, so we could have a get-together according the vibration. According to him this sounds more like a natural frequency thing than a spinning item being out of balance... Will be doing some measurements with him later on.

 

[Valkman]

Just doing some out of the box thinking here. Is there a chance that the fuel map gets more aggressive at 3k? If the throttle bodies needed adjusted and say one or two cylinders were off from say 1.7 milla secs to 2.0 milla secs, would the slight misfire cause a vibration?

I drove my car using live data and there seems to be nothing out of the ordinary during that moment. No major VANOS timing change, no huge fuel feed change etc. Not even knock signal ignition retardation (being triggered by vibration).

 

[Valkman]

Yes, I realized before, that the first vibe is somewhere at 1500 rpm and the second after 3000 rpm... but the biggest news is, that I tried today at work and got those same 3200 rpm vibrations on a 2006 Range Rover with 4.4 liter V8! That luxury car has almost no vibrations from the road surface through wheels, not to mention from the drivetrain/engine. But bringing the revs up at standstill brings the vibration to the body exactly at 3200 rpm... Are we talking about characteristics on big V8 engines, that for some reason are transfered to the body in our cars more stronger?