W126 Front End Rebuilt, Aligned, Slight Vibration? - PeachParts Mercedes-Benz Forum

JamesDean · #1 09-17-2013, 08:48 AM

Hey everyone,

The 420 is experiencing some (what feels like) up/down vibration when driving down the turnpike 55+

The front end has been rebuilt, everything except the center drag link and idler arm bushing has been replaced. Springs, shocks have been replaced too.

I'm not quite sure would cause this.

Tires out of balance?
Wheel bearings improperly torqued?
Motor Mounts?

Maybe the alignment? I do know that when I am in the middle or left hand lanes on the turn pike I have to hold the wheel at near 2 o'clock to drive straight. If I don't it will pull left. If I am in the right hand lane it drives better, only slightly adjustments right of center are needed... I'm not sure what that means. My 300D drives the same way. Frankly I find it largely annoying. Not sure what can be done?

Any ideas would be welcome.

Thanks!

dlssmith · #2 09-17-2013, 11:32 AM

The drag link and idler arm bushing could be responsible, but in a small way. If they're old, replace them. The pulling at speed on the highway is more concerning to me. I'd be looking at the alignment again if everything else is new. Tires can go out of balance, loose a weight etc., or just from excessive wear. Have them checked too. This car should track pretty straight on the road unless the road has a high crown.

JamesDean · #3 09-17-2013, 11:36 AM

The vibration is not jarring but it is noticeable and something needs to be done to fix it.

The pulling is annoying. but it only does it in the center and left lanes. in the right lane, it operates straight. I dont think the turnpike has a particularly high crown. I'm 99% sure my 300D drives the same. I had them both aligned at the same place..

Both of the cars (300d and 420sel) that they aligned drive similarly:

Right lane, mostly OK, slight adjusting needed, mostly to the right.
Middle lane, need to hold wheel at 2 o'clock to maintain straight
Left lane, same as right lane.

Since this is how it is on BOTH cars...this leads me to believe that maybe they set the toe on the car so that the car naturally pulls to the left to compensate for the road crown.. maybe?

o0norton0o · #4 09-17-2013, 12:18 PM

I've had this issue, and I had a bad drag link, It was obviously shakey. I replaced it and 95% of the shimmy went away. On my 560, the rest went away when I had the tires balanced. I have found this is an issue with these cars. For my car to float like a magic carpet on the hiway, (which is the feeling they give when everything is perfect) the tires need to be well balanced and the front end has to be solid everywhere.

At one point I mentioned the vibration to a mercedes mechanic and he said to me in a very cagey fashion,... "the more new front end parts you replace, the better it will ride". I checked out all the front end joints, found the sloppy drag link, replaced it and the car drove much better. I wasn't looking for "brand new" performance, so I had the tires balanced and was satisfied with the ride quality. I'm sure it could be even better, but "good" was good enough for me.

Drag links need to be solid...

Stretch · #5 09-17-2013, 02:53 PM

If you think it might be tyres - swap back with front

Tick one thing of your list of possibles

S-Class Guru · #6 09-17-2013, 05:11 PM

James, these are the most sensitive cars to tire imbalance I have ever seen. I have actually put on brand new tires a couple of times and been unable to get them to balance well enough to be acceptable. And if I get a good set and cross-rotate them per the book, they quickly develop the shakes and are uncureable. Seems Michelins have the best track record for me so far, rotating only F-R without crossing.

If it pulls left that hard it may well be caster adjustment. Of course camber or rear-end toe and tracking(non-adjustable) can cause that somewhat also. Unfortunately, most shops never ever touch caster and camber adjustments, unless it's waay off; and they can't do anything about rear end toe or steer-ahead on the 126. In my experience toe does not affect steering pull too much; but what it does do is promote uneven wear on the tires, which soon translates into imbalance that cannot be cured with any dynamic rebalancing - just gotta throw the tires away. Right now I have Michelins that went 35k miles (a record) before they got worn irregularly enough to bounce at 60 MPH. Did a good rebalance and no help at all. Just gotta get new ones.

Funny, when I bought my car at 9k miles 22 years ago, I noticed some wear on the outside of the front left. after 1/4 million miles, a dozen sets of tires, numerous alignments, and rebuilding everything in the suspension/steering at least once, I still get the same wear pattern on that left front.

DG

pmckechnie · #7 09-18-2013, 10:25 AM

First thing to do is swap the front tires side to side. I have seen this problem several times where pulling is caused by the tires and reversing the direction they turn fixes the problem. I have never seen this happen because of rear tires but I guess it could happen also.
Also, the amount you need to turn the steering wheel to correct for the pulling bothers me also. On a 126, turning the wheel from say 1 o'clock to 2 o'clock is a lot. The wheel should be straight at all times on a straight road. There must be an alignment problem somewhere. There is an alignment hole on the steering box that needs to be set when doing an alignment. I'm sorry, I can't remember much more than that it is there somewhere and should be used to make the steering wheel straight while going straight. Most alignment shops just tie the wheel straight and align everything else to that. Mercedes cars need the steering box locked in the straight position and then align everything to it. I hope that makes sense.
Look for the vibration after the other problems are fixed. These cars are very sensitive to tire balance but out of balance tires won't cause pulling.

Just my thoughts.

Paul

Ozarkdude · #8 09-19-2013, 09:46 AM

I did alignments professionally when I was young. Tire shops only use the alignment bay to sell parts, often un-needed parts. They even sent me to a class put on by MOOG on how to find worn parts to make sales. The clowns doing the alignments are under pressure to get you in and out. They simply dont have the luxury to spend 2 hours doing a proper alignment for $69.

Honestly, the dealer may offer the best service, but you'll pay for it. Or, DIY. Its not rocket science, and you can no doubt do a much better job than what you have presently. Seriously, that both cars drive the same is pretty telling of hack work. Provided the front end parts are reasonably tight, they should drive like new after a proper alignment. Which starts with centering and locking the steering gear with "the tool", by the way.

JamesDean · #9 09-19-2013, 10:19 AM

Here is a little history.

This alignment stuff all started with my 190E. I would take the car to Hovis Tire in Cortland and have them do the alignment on it as no other shops would could do it and I wasn't about to pay the dealer at that time. All the numbers on their print outs looked in spec but the car still drove lousy. The car had 200k on it so the front end and gear box were tired.

Fast forward to fall 2012. I'm fully employed now and can afford to rebuild the 190's front end. Everything except new springs, tie rod assemblies (previously replaced) and center drag link were replaced with new, good brand, parts. Even the steering gearbox. Drove pretty well!

At this point in time I had the 300D back on its feet from its transmission incident. I put that car into daily driver mode and parked the 190 for the winter.

In December I got new winter tires and noticed that the car pulled one way or the other. I'd also put new front springs on a few weeks prior so I figured ride height changed and a new alignment was needed. I took the car to Hovis and had it aligned. It was absolutely horrible, despite what the print out said. Road variations and imperfections were directly translated into my steering wheel. It was annoying.

I gave in and gave it to my local Mercedes dealer who was much better to work with and was more interested in resolving my issues than Hovis. Road variations and imperfections were absorbed by the suspension system and steering was notably improved.

So I took my 190E to them as well. I haven't driven the car much recently so I do not recall its road behavior.

And recently the 420SEL to them as well.

The only thing I have noticed is that both cars like to pull to the left when in any lane other than the far right lane. The dealer has done a much better job than my previous alignment places but its not perfect....so what do i do?

I realllllly do not want to DIY alignments...

The 190E's front end is 1 year old
The 300D's front end is only 4 years old
The 420SEL's front end is brand new.

Ozarkdude · #10 09-20-2013, 12:56 AM

First, all dealers aren't the same, and all mechanics aren't the same. Some are very conscientious, some could care less. Like I said, the dealer "may" be better. But equally, they may not, either. You could have a great dealer, but maybe they have a not so great alignment guy. Or, perhaps you just need to go back and tell him it pulls to much to the left. If he can alter caster a bit it will help it.

JamesDean · #11 09-20-2013, 10:39 AM

Ozark, right. I understand. I do know that their alignment guy did a vastly better job than my previous alignment guy. However the job is not yet perfect.

Interestingly enough I noticed a very very similar vibration in my 300D. It felt like the same vibration I felt in the 420SEL. I wonder if the alignment could cause such a thing? Not quite sure how but maybe?

Either way I shall call up Fred Martin Mercedes and have them look at the caster and see if that fixes the pull to the left. As Paul said, it shouldnt pull in any lane but I'm not sure how that is accomplished?

JamesDean · #12 09-20-2013, 08:09 PM

Here are some pics I took while driving home.

420SEL

These are clearer.. This was taken in a construction zone and the lane i was in would actually have been the left most lane under normal conditions (as it is now actually)

300D

This was in the middle or left lane. Its very slight but i think you can see the wheel angle.

pmckechnie · #13 09-20-2013, 09:14 PM

I am not sure what to say other than the alignment is off. If the steering box is locked when the alignment is done and the steering is straight then the car should go straight, hands off. Tires can cause this problem but if you swap them side to side the problem will usually go away, not pull the other way. I never understood why the problem goes away instead of pulling the other way, but I have seen it many times. The first time I saw this was after alignment on an old Buick Rivera. It pulled to the right, the steering wheel was not centered and I was not happy. The tech swapped the front tires and the problems went away.

Paul

TOPGUN · #14 09-20-2013, 09:53 PM

Carr Auto Repair in Warren may be able to help.

JamesDean · #15 09-21-2013, 10:13 PM

Quote:

Originally Posted by pmckechnie

I am not sure what to say other than the alignment is off. If the steering box is locked when the alignment is done and the steering is straight then the car should go straight, hands off. Tires can cause this problem but if you swap them side to side the problem will usually go away, not pull the other way. I never understood why the problem goes away instead of pulling the other way, but I have seen it many times. The first time I saw this was after alignment on an old Buick Rivera. It pulled to the right, the steering wheel was not centered and I was not happy. The tech swapped the front tires and the problems went away.

Paul

So in any of the lanes on the turnpike, regardless of road crest, the wheel should go straight?

I have a feeling they did not use the locking device on the gearbox but I could be wrong. Its been 9 months since they touched the 300D so I'd probably have to pay for another alignment....Its only been 3 weeks for the 420...might be able to get them to fix it at low cost or no cost.