528e oscillating engine vibration

Nine months ago, I lost the reference pin on my 25 year old flywheel, and had to have the flywheel replaced. Picked up the car and immediately noticed an oscillating vibration around 1500-2200 rpm, with a pulsating rhythm every two seconds or so. Felt it in the seat, steering, etc. Took it right back, and they weren't helpful, said they could feel nothing, or claimed it was a driveshaft problem and unrelated. Like a fool, I didn't push it, and what was initially just mildly irritating quickly began to drive me insane. I have spent the last 9 months trying to fix the problem, using a better mechanic.

It's worse when cold, worse under load, but is definitely still present when not moving and when in neutral. Motor mounts and transmission mounts have been replaced, I've had the flywheel pulled and checked for balance by an independent machine shop--and it's perfect. My new mechanic was careful to check its re-install closely. Problem still there.

My only remaining thought is that it's an ignition timing issue. The crank position sensor has a really sad looking connection under the hood (first mechanic said he put a lot of "goop" on it to keep the connectors together--I'm not quite sure why he was even messing with that connection in the first place), but can a bad crank position sensor or bad sensor connection, which causes faulty ignition timing, cause a pulsating sort of vibration? Or would it be a constant vibration?

Any ideas? This thing is driving me freakin' nuts. This engine has 425K miles on it, and it's never been torn down, and still runs like a champ. But with this kind of age, I have concern that this vibration will eventually cause other problems.

Did you ever check the drive line. It could quite possabilty be the carrier barring and or mount

I took it to a shop specializing in drive shaft balancing. They did not remove the drive shaft, but they ran in gear on the rack, and noticed the problem in neutral, and said it was not a drive shaft problem.

I'm assuming that by "drive line" you mean drive shaft. Am I right?

The issue definitely seems to be from the gearbox forward.

im not sure whats wrong with your but when the pin came off the flywheel how could u tell that the pin was the problem i am havein a no spark problem with my 87 528e and i was told that might be the problem

There is actually a part of the bell housing they can take off, one guy looks in with a flashlight, another guy turns the crankshaft, and the first guy keeps looking until he sees either the pin or where the pin broke off. In my case, the broken pin actually fell out. This is all hearsay, because I never saw the pin or the flywheel. The sensor is magnetic, so the pin could be stuck to the sensor when it is pulled off the bell housing. Again, all hearsay, maybe someone who knows what they are talking about can educate us.

It sounds like something's out of balance, or damaged. Harmonic balancer? Driveshaft guibo maybe? Did they reassemble the driveshart in the same position it was in originally? What about the center bearing, did you check that carefully? They're supposed to be preloaded on installation too. Was the drive shaft bent? I had that happen once because some moron damaged it with a hoist. Broken spring or suspension component; dogbones, subframe mounts, etc? Jack up the rear and put in in gear and see if you can reproduce the vibration. Try to eliminate as many things as possible.

The driveshaft specialist said the shaft would not make the vibration he felt, and it checked out OK to the point he said taking it out would do nothing to find the problem. He said with the vibration in neutral, driveshaft and suspension elements were not the culprits. (FYI, I have had the front end rebuilt--all new Miele components and new shocks--and the rear end rebuilt--springs and shocks, and subframe bushings, so the car is riding and handling like it did 20 years ago, except for the damned vibration, which clearly seems to be coming from the engine, IMO.) The harmonic balancer has been checked. I'm still waiting for someone who knows ignition to tell me if bad timing in an L6 engine can set up a pulsating vibration like I describe.

Thanks to erowe, speedracer401, and catso for your input so far.

Originally Posted by older man

The driveshaft specialist said the shaft would not make the vibration he felt, and it checked out OK to the point he said taking it out would do nothing to find the problem. He said with the vibration in neutral, driveshaft and suspension elements were not the culprits. (FYI, I have had the front end rebuilt--all new Miele components and new shocks--and the rear end rebuilt--springs and shocks, and subframe bushings, so the car is riding and handling like it did 20 years ago, except for the damned vibration, which clearly seems to be coming from the engine, IMO.) The harmonic balancer has been checked. I'm still waiting for someone who knows ignition to tell me if bad timing in an L6 engine can set up a pulsating vibration like I describe.

Thanks to erowe, speedracer401, and catso for your input so far.

I think bad timing could, but beside the reference sensor there's the possibilty of a timing belt issue.

Guess what? Yep, new timing belt done 3 weeks ago. I was within 10K miles of needing one anyway, but I did it early to diagnose, and the vibration was still there.

Thanks for hanging in there with me on this.

Originally Posted by older man

Guess what? Yep, new timing belt done 3 weeks ago. I was within 10K miles of needing one anyway, but I did it early to diagnose, and the vibration was still there.

Thanks for hanging in there with me on this.

Try a cylinder balance test, or pull one plug wire at a time and see if there's any effect.

So, the idea is if you pull one plug wire and there is no effect, then that's the problem?

Originally Posted by older man

So, the idea is if you pull one plug wire and there is no effect, then that's the problem?

That's one way. It might help in diagnosing the problem. It could also be transmission related. Is it a manual or auto trans? If auto, could be a torque converter issue. If manual could be the input shaft, bearing, or pilot bearing, or clutch issue. You have to narrow it down more.