[goodmaj]

Did they check the bushings that hold the exhaust above the center support? #6 on the drawing.

Update - had the car at Indy #2 this morning. Originally, their thought was to change the transmission fluid back to OEM from Red Line as a start. I already had the appt so I thought why not go in and discuss a lot of the stuff in this thread. They put the car up, and without prompting, started looking at the mounts. They took off the connecting support (#5) and noticed some wear on the exhaust. It was in the shape of an oval, maybe pea-sized or slightly bigger, driver side. They didn't have replacement mounts (#6) in stock so they put some shims in to lower the plate. We decided to hold off on the transmission fluid change for now. And, they didn't charge me a dime.

I then drove to the office which is all highway and played around with the gears and RPMs. I'd say the problem is still there but I'd also say it's better than it was. They ordered up some mounts just in case.

I'm cautiously optimistic we're on to something. It might be time for a mount-a-palooza. I also got a look at the guibo, I know this is DRod's pet peeve but it looked really fresh. More to come.....

 

[mattmor]

Great news on the improvement. Keep us posted.

 

[D-RodM5]

... I also got a look at the guibo, I know this is DRod's pet peeve but it looked really fresh. More to come.....

hiha ...I'm tellin' you that guibo will bite ya if you don't look out for it Glad to hear of the progress :M5thumbs:

 

[meepmeep]

Any updates? This is the best vibration thread I've read here in a while. I'm tracking down the same thing. 2500-2800 RPM while driving, harmonic. Have had tires balanced on a Hunter machine, and wheels checked--all true. Front and rear suspension is new, engine/tranny mounts replaced. Guibo/driveshaft/diff bushings all new. None of this was done to fix the vibration, but it is still out there. I have exhaust hangers in the garage so I'll throw them on this weekend and see how it goes.

 

[68FB]

I did a bit of work on this too. I welded up the split seam on the cat inlet which made the car a bit quieter but did not improve the 2000 rpm noise and vibration.

I removed the exhaust support that bolts to the back of the tranny and found the small rubber mounts, item 12 below, as hard as rock, so I left the support off while I wait for new mounts.

When I ran the car on the driveway at 2000 rpm, the section of exhaust between the headers and the cats vibrated a lot. This was with the support removed. And I heard the noise loudly from both cats when touching the stethoscope probe to them. Loose internals?

Then while driving, I found the 2000-2500 rpm noise was worse. I could hear it in the higher gears as well as 2 to 4. I am curious to see if replacing the support with new mounts will quieten it down again.

I am beginning to think this might be either an acoustic resonance in the exhaust or engine vibration coinciding with a structural resonance of the exhaust system at 2000 rpm.

I got a vibration meter to find out what frequency the exhaust is vibrating at but I need to find a way of attaching the probe to the hot pipe.


Goodmaj, have you had a listen underneath yet? Check out your cats with a stethoscope.

 

[goodmaj]

Alas, I'm not nearly as prepared with tools and stethoscopes.....however, my car is going into the shop on Monday evening for a re-repair of the driver's side vapor barrier. I've already prepped them that I want a full inspection of the exhaust system from front to back. I will include mention part #12 and also tell them to hit it with a stethoscope as you describe. Will post results.

Interestingly, it seems that the warmer weather has softened the vibration ever so slightly, it's a little less noticeable now.

 

[goodmaj]

Any updates? This is the best vibration thread I've read here in a while. I'm tracking down the same thing. 2500-2800 RPM while driving, harmonic. Have had tires balanced on a Hunter machine, and wheels checked--all true. Front and rear suspension is new, engine/tranny mounts replaced. Guibo/driveshaft/diff bushings all new. None of this was done to fix the vibration, but it is still out there. I have exhaust hangers in the garage so I'll throw them on this weekend and see how it goes.

Meepmeep, there's a second thread on this as well that might shed more light on your situation....unless you've got the same issues as 68FB and myself.

http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/235809-engine-knocking-sound.html

 

[mattmor]

I did a bit of work on this too. I welded up the split seam on the cat inlet which made the car a bit quieter but did not improve the 2000 rpm noise and vibration.

I removed the exhaust support that bolts to the back of the tranny and found the small rubber mounts, item 12 below, as hard as rock, so I left the support off while I wait for new mounts.

When I ran the car on the driveway at 2000 rpm, the section of exhaust between the headers and the cats vibrated a lot. This was with the support removed. And I heard the noise loudly from both cats when touching the stethoscope probe to them. Loose internals?

Then while driving, I found the 2000-2500 rpm noise was worse. I could hear it in the higher gears as well as 2 to 4. I am curious to see if replacing the support with new mounts will quieten it down again.

I am beginning to think this might be either an acoustic resonance in the exhaust or engine vibration coinciding with a structural resonance of the exhaust system at 2000 rpm.

I got a vibration meter to find out what frequency the exhaust is vibrating at but I need to find a way of attaching the probe to the hot pipe.


Goodmaj, have you had a listen underneath yet? Check out your cats with a stethoscope.

I replaced those small rubber mounts for what it's worth. At the time it didn't seem like I was changing much, but maybe it helped more than I knew

 

[Thin Man]

I did a bit of work on this too. I welded up the split seam on the cat inlet which made the car a bit quieter but did not improve the 2000 rpm noise and vibration.

I removed the exhaust support that bolts to the back of the tranny and found the small rubber mounts, item 12 below, as hard as rock, so I left the support off while I wait for new mounts.

When I ran the car on the driveway at 2000 rpm, the section of exhaust between the headers and the cats vibrated a lot. This was with the support removed. And I heard the noise loudly from both cats when touching the stethoscope probe to them. Loose internals?

Then while driving, I found the 2000-2500 rpm noise was worse. I could hear it in the higher gears as well as 2 to 4. I am curious to see if replacing the support with new mounts will quieten it down again.

I am beginning to think this might be either an acoustic resonance in the exhaust or engine vibration coinciding with a structural resonance of the exhaust system at 2000 rpm.

I got a vibration meter to find out what frequency the exhaust is vibrating at but I need to find a way of attaching the probe to the hot pipe.


Goodmaj, have you had a listen underneath yet? Check out your cats with a stethoscope.
View attachment 239761

Are you getting any codes for the cats?

 

[goodmaj]

I'm not getting nor have I ever gotten any codes

 

[68FB]

Are you getting any codes for the cats?

I get a b3 for the bank 2 cat every couple of months. I just clear it.

From what I have read after having cheap aftermarket cats on an old beater start rattling on me after a couple of months, the honeycomb is supported in the steel can by a layer of high temp matting. Cheap cats, the matting falls apart if the cat runs too hot from rich running. On the M5, I was just thinking the honeycombs could be moving around a bit from acoustic resonance pressure waves, but no damaged. Just keeping an open mind.

 

[Thin Man]

68FB, I have a vibration not too different from what you describe. I am getting a B2 code for the cats. I wonder if there is a connection. I would not have thought of it until you posted the exhaust diagram showing the cats. The fact that you have cat codes seems to indicate a possible connection. I'm obviously not eager to replace the cats given the expense.

 

[goodmaj]

Well, it was a good idea, or at least I thought it was a good idea to have the stealer look at the exhaust from top to bottom. Their response was all M cars resonate, nothing wrong. Sigh.

 

[D-RodM5]

Sorry to hear about the dead end result. Are you going to let it ride for a bit or address something else right away?

 

[goodmaj]

Not really sure at this point. It's pretty frustrating when someone says it's normal but then in the next sentence say there's a guy who works there that has one and it doesn't exhibit what I'm seeing. I'm half tempted to drive it up to Cincinnati and let EAG play with it for a week. Or hope that 68FB comes up with an answer, but that's pretty lame because I feel like I should be doing something on my side.

 

[68FB]

I replaced those hardened rubber bushings on the exhaust support at the back of the tranny but it made little difference. I have given up for now.
Interesting comment about M5's resonating. I don't suppose they meant ALL M5's resonate but it probably means they have seen some and couldn't fix it.

 

[Crispie]

Same issue, heavy vibrations under heavy load in lower rpm though

Great vibration post.
I have exact same issue, engine vibration around 2000 rpm with disengaged clutch.
Further more, I don't know how it's supposed to be as I recently bought my M5.
When driving in gear around 1000 rpm and floor it, I get heavy low vibration in the entire car. I strongly suspect it's the DMF that have worn out. When coasting and I let go of the gas, I feel like there is a play between gearbox and engine, this is also visible when the car is on a lift: While stopped/shut off and in gear, I can turn the rear wheels back and forth what equals 10 cm before the DMF creates resistance. My RMS is leaking so I need to change the clutch anyway due to it have been lubricated :sad1:
My beast is pushing almost 200k km but aside of these vibrations and the annoying 2nd gear synchro gear change when cold(has this always been a problem since new on these beasts??) it drives like angles sing! The worst day can definitely be saved by a drive in this made I heaven super car :goldcup:

Picture from dealer when I picked her up

 

[68FB]

When driving in gear around 1000 rpm and floor it, I get heavy low vibration in the entire car.

Congratulations on the new car. They're a lot of fun.

I suggest you don't floor the gas pedal at 1000 rpm. It's hard on the rod bearings as the engine doesn't develop full oil pressure to protect the bearings until 1500-2000 rpm, but the VANOS allows it to make quite high torque, which is what loads up the bearings.

 

[Crispie]

Congratulations on the new car. They're a lot of fun.

I suggest you don't floor the gas pedal at 1000 rpm. It's hard on the rod bearings as the engine doesn't develop full oil pressure to protect the bearings until 1500-2000 rpm, but the VANOS allows it to make quite high torque, which is what loads up the bearings.

Thanks. Duly noted, did it just to check vibrations.
Did a spin around today, engine stalled, uneven running followed. Threw 1 Code: cylinder 1 misfire (don't blame it). Reset it, and she fired up normally. Afterwards low end torque has been reduced quite a lot. No codes present, can barely smoke tyres in 2nd (driving in 2nd at 2500 rpm and gun it) it use to do same in 3rd... High rpm power still available 130 l/h at redline WOT. I have a feeling that the engine might be spun the wrong during the spin around (reversing with engaged clutch, 3rd gear and stalled engine.... Yes, I know, I'm an idiot!), and I'm afraid this have fubard something up, I haven't the VANOS insight to know wether this is certain destruction or what ...