khutchinson22

Slight vibration that comes and goes starting at around 70mph and smooths out around 95mph. I say comes and goes but it is consistent. If I hold constant speed it will vibrate, smooth out, vibrate, smooth out......continuously. Wheels balanced, road force test done, not sure what else to check. Been to 3 mechanics one is a European mechanic and one was a MB specialist. The boots on the front struts are broken but they are still operational. Rodeo test performed fine. With car in the air the front wheels can be pushed up and down about an inch. The rears cannot. I'm not certain the struts are causing this issue as they are working fine otherwise. Just want to be sure before shelling out the cash for new struts.

Does this sound like struts or is there another possible issue?

fireman685

Motor, transmission mounts and driveshaft flex disks. Check those.

khutchinson22

How do I test the flex discs? Are the mounts just a visible check?

fireman685

Disks are visual inspection. Looks for cracks in the rubber or obvious damage/degradation.

As far as motor and trans mounts, how many miles on the car? Do you have a vibration while at idle? I've got my car scheduled to have these replaced next week. Vibration at idle(motor mounts) and course acceleration (trans). Same symptoms as my Lexus and now it's smooth as silk with new mounts.
Something else to consider is your alignment and other front suspension items.

khutchinson22

100k on the clock. No vibration at idle. There is no increased vibration upon acceleration. I will check the drive shaft. Is it located at the rear of the vehicle? I have never seen a rubber mounted drive shaft.

fireman685

There should be two. One at each end of the shaft.

khutchinson22

Is this simply a visual inspection or should I be looking/feeling for something specific?

fireman685

With my Lexus it was a simple visual inspection. If you see any cracks in the rubber then replace it. What appears to be a tiny benign crack while sitting still may be a much bigger one while under a lot of torque and rpms. And of course if you see any pieces missing from it, well then it's obvious. Google CL 55 flex disks. It'll show you good and bad ones.

khutchinson22

SOLVED!

Oddly enough this had nothing at all to do with drivetrain. The idler pulley bolt hole on the front engine cover had been stripped out causing the idler pulley to wobble.

adamls2

Interesting... I have the same type of vibration as mentioned, and I has my motor mounts, tranny mounts, flex discs and wheels/tires all checked and they are all 100%. I'd be releifed if its the idler pulley! I know they are common problem.

khutchinson22

Welp, I was jumped the gun on that one. It is NOT solved. I found the same issue on another part of the forum and this was the description.....

"My vib is always there, no matter the condition of the road... it goes away passed 50mph. You got me thinking though about the rear suspension, the rear of my car sags more than it should, but then again the vib comes and goes always at the same speeds and I can feel a sort of oscilation in the vibration that actually fades in and out with perfect timing... it's hard to explain."

I feel like this is a better explanation than what I had given. Mine happens at a higher speed but the symptoms are the same.

The dealer suggested the pulsation dampener as a possible problem but didn't feel confident enough to suggest I spend the money. They did, however, inspect the motor and tranny mounts and the flex discs and they said they looked fine.

I read in another thread that because this is a heat related issue that the flex discs could still be the culprit even though the APPEAR to be ok that once heated or cooled could affect the vibration more or less because of hardness in the rubber. This sounded plausible so I am going to go ahead and change them out as soon as I can.

fireman685

If your pulsation damper is out you're going to hear a droning sound as soon as you start the car. Also you'll most likely have warning dings when going over big bumps. Check your abc fluid also. If the level has suddenly dropped then a ruptured damper (or any other accumulator) could be the culprit. I had never had any road vibrations when mine were bad. Just a lot of noise and uncomfortable ride.
Keep us updated on how the flex disk replacement goes. I hope this solves the problem.

khutchinson22

I don't hear any kind of droning sound but I do get dings going over large dips in the road at high speed. I'll check the fluid level.

fireman685

Sounds like an accumulator is blown. If not the pulsation damper then most likely the one on the front valve block, which incidentally is the same part number as the pulsation damper. I went ahead and replaced all four of mine cause if one goes is not long before the rest do.

khutchinson22

Went out to the garage this morning to find my drivers side all the way down. I got in, started it and raised & lowered it a few times and now it seems fine. Not sure what caused it. It has been cold here lately but no colder than the last few months so I don't think that is what caused it.

desired_speeds

It's your center driveshaft. either than angle is wrong or it's out of balance or u-joint is binding. When was the last time you replaced your engine mounts? I noticed that prolonging the replacement of failed engine mounts causes these issues.

khutchinson22

I called a local drive shaft place and when I told them what I had they said they couldn't help and that they only work on American cars.......

I would prefer not to send it off for repair since it's my daily driver.

fireman685

A friend has an SL500. On really cold mornings his car will sag.

fireman685

What's the latest? Did you find the source of the vibration?

khutchinson22

Not yet. I've more or less given up on it until whatever it is shows enough signs of wear to make itself obvious.

fireman685

I was curious. I've developed the same kind of vibration. I'm going to go with a road force balance first since I have new tires on the rear that were balanced the regular way.

khutchinson22

They can be tricky. I had it road force tested and that didn't give any results. I took it to the dealer and all mounts, flex discs, etc looked ok. They said it MIGHT be the Pulsation dampener but couldn't say with enough certainty to justify replacing it.

That's where I stopped.

Good luck. Let us know if you find anything unusual!

fireman685

All four of my accumulators are new so I'm not concerned with those. Engine and tranny mounts are new. Vibration became more noticeable during my road trip to Kentucky and that was right after I had two new tires put on the rear. My front tires still have like new tread but noticed they were starting to cup a little and get noisy so had them swapped on the front rims and re-balanced just last Friday. I've since been to Iowa and back and notice more vibrations like you described. If a road force balance doesn't do the trick then I'll look into the drive shaft. I've got 92k miles on my car now and the flex disks could probably stand to be replaced anyway.