Garage => Mechanicals => Topic started by: daantjie on 25 March 2019, 08:35 AM

Title: 6.9 Steering feel?
Post by: daantjie on 25 March 2019, 08:35 AM
Hi guys

Calling mostly the 6.9 guys here.  I took out the ol' girl on the weekend to road test after I replaced:

1) Steering Coupler - that clang-clang was driving me to strong drink and loose women!
2) Idler arm bushing - did not seem too rough, appears to have been changed out at least once before my ownership
3) Drag link - old one was not too rough, but boots were shot
4) Steering damper - I had a fairly new one in there already, but I had a new one as well, so I figured what the hell and swapped it out as well.
5) Tie rods are new as well.

Once again confirmed my love/hate relationship with suspension work.  It can be brutal but very satisfying before and after ;)

Road test was nice, steering does feel tighter for sure, but from my experience I think this was mostly due to the new steering coupler.  It still feels fairly vague to me.  My daily driver is a little Honda Civic and you can throw that thing around like crazy.  I know it's probably not fair to try and compare the 2 as they are different systems and of course 30 years apart in age, so...

Of course I need an alignment as well, but I doubt this would affect steering response?

But still I think there is something amiss.  Only thing left now is steering box I would think ::)  I have to assume that it is the original box, and thus it is probably done for.  I have not attempted to adjust it in situ, but on the 6.9 this is all but impossible due to the location and sans lift.  I am stubborn enough to try it (maybe ;D), but I would assume the nut must be extremely tight on there, so the best approach would likely be to do this on the bench?

Title: Re: 6.9 Steering feel?
Post by: raueda1 on 25 March 2019, 09:54 AM
Wow Daniel, lots of work!  Now I'm wondering if I should do more too.  I've inspected all my the suspension stuff on a lift and it al seems solid - no loose bushings, rattley parts or anything like that.  Anyway, I'm not entirely clear on the question but I'll comment on my experience FWIW (probably not much).  Prior to coupling replacement my steering WAS very vague and had the well known bang over bumps.  The coupler fixed all that.  There's no slop now, it's very tight. The slightest movement in the steering wheel translates to corresponding change in direction.

That said, the car does have a "big car feel."  I drive much smaller, lighter cars all the time and I can't say that the 6.9 is worse in any way, just different.  There's much more mass to move in a quick lane change for example.  And there's the suspension which contributes as well.  I think it the magic carpet ride goes a long long way to reducing a "crisp" handling feel of smaller cars or stiffer suspensions.  But it still handles great.  i drive twisty mountain roads all the time and it does great, just doesn't feel like a sports car or BMW.  I'm also running 235/60-15's.  They made an enormous difference in handling.  The car came with some kind of 14" Michelin snow tires which were just awful and probably dangerous.

Hope that helps, maybe, kind of?  ???  BTW, car held height amazing well over the winter despite long periods of inactivity and wild temperature swings.  Must be those leveling valves, ehh?

[edit:  Just reread your post. Compared to your description I can't say I have any sense at all that "there is something amiss."  Or, if there is, I'm too insensitive to recognize it.  As another reference I swapped 6.9's with another guy at the last Lodefest cause we wanted to do a comparison.  It was a very spirited morning drive on twisty Oregon mountain roads.  He specifically commented that my car really had a tight, new-car feel to it compared to his.  I noticed the same thing, so I do think mine probably is pretty close to what  it ought to be.  So, if you think something still isn't quite right, then I'd guess that it isn't.  Wish I could provide direction on what exactly that might be.....]
Title: Re: 6.9 Steering feel?
Post by: daantjie on 25 March 2019, 10:52 AM
Thanks Dave!  Yes in all fairness, I must admit that I do not drive the car enough to really have a good baseline to compare to.  I drive it mostly in the summer, and even then it is not a regular thing.  I know this is not good in general :-\

I am probably also not running the best tires to be honest.  I have the original 14" Bundt wheels on there, and as we all know tire choices are few and far between.  I am running these - Falken Sincera SN211 P205/70R14.  I know the original Michelin tires had the reinforced sidewalls and such, but at $500+ per tire that ain't gonna happen...

Again as I hardly drive it, I am kind of hard pressed to spring for a full set of 15" Bundts plus new tires, but then again safety is safety ::)

Title: Re: 6.9 Steering feel?
Post by: rumb on 25 March 2019, 01:48 PM
If you decide to pull the steering gear box just leave the big nut on the pitman arm and remove only the tie rod ends. loosen the flex coupling, remove 4 bolts and be prepared to catch a very heavy box, best to have a jack supporting it. For $5-6oo you can have C&M hydraulics rebuild it.
Title: Re: 6.9 Steering feel?
Post by: daantjie on 25 March 2019, 03:08 PM
Thanks Robert, yes I'm not sure if I want to chase this dragon any more at this time.  I will probably get annoyed to the point where I want to tackle it again in the future I am sure...
Title: Re: 6.9 Steering feel?
Post by: Jed on 25 March 2019, 06:45 PM
Hey Daniel
Yes you did a lot.  I absolutely would agree with rueda1 that the car has a 'big car feel' which in my opinion drives better without that sensitive steering feel.  Ill bet after you do the alignment it will much better.  having changed the tie rod ends your alignment must be off which can really change the steering 'feel.' I think i have a little tiny bit of slop in my steering which is what I expect from it.  Actually I think it is a bit forgiving and allows the car to go straight easier...if that makes sense.

I have a mid eighties Bentley with a a featherlight steering that is ridiculously sensitive and it really takes away from the drive. It is so sensitive it is literally hard to keep the car straight and between the lines.  I am told by other owners that is normal for those cars. I much prefer the forgiving steering of the benz.

Let the dragon be and let us know how much the alignment helps.
I am sure you will have something else to address soon.....I am currently on my second go around with the acc heater servo in 2.5 years...and it is not going well  :'(
Title: Re: 6.9 Steering feel?
Post by: daantjie on 25 March 2019, 07:33 PM
Thanks Jed indeed I think it's time to go back to "first principles" here ;)
Title: Re: 6.9 Steering feel?
Post by: TJ 450 on 25 March 2019, 07:38 PM
You’re never going to get that rack and pinion precision, although if the steering gear is within spec and everything else is good, it should feel pretty tight.

Extra play in the steering gear is going to have a huge impact on the response and the wheel alignment also will have a large impact.

When I drive my 6.9, it’s not far off feeling like a modern car, just a bit of freeplay, but less than 1". Its still relatively precise.

Title: Re: 6.9 Steering feel?
Post by: revilla on 26 March 2019, 02:28 AM
I recently changed the tie rods, central link and its shock-absorber.  The handling significantly improved, but it was only when the day after they did the wheels alignment that the tight steering feel came back.  I'm happy with the handling improvement! Yes there's some light play on the wheel, but I'm not near capable to adjust the steering box myself, so I leave it alone.  Plus I understand that if you don't adjust it well it might accelerate the wear of its internal components.  So better not to touch it unless you know what you're doing, I don't  :o
It might be a thing of expectations and baseline comparisons.  I don't expect mine to handle like a light modern car.  It's a different animal...
Title: Re: 6.9 Steering feel?
Post by: daantjie on 26 March 2019, 11:31 AM
Thanks for all the feedback guys, I will make work of the alignment soon (hopefully) then report back.
I need to find a competent shop (good luck) as I fear most local shops will not be able to set up a 116 properly.
Title: Re: 6.9 Steering feel?
Post by: Mick74 on 26 March 2019, 01:42 PM
I found this thread very interesting. My steering is not great, to say the least. The coupler needs repacing, there is play in the box and it's leaking.
I've a new coupler and rebuild kit for the box on the way this week and the car is going to the shop on Thursday for these and numerous other jobs. Once these are fitted (if the box can't be revived, I'll have to source a second hand one) I'll see if I need to replace anything else.
Looking forward to trying the car post work. I'll update as I go along.
Title: Re: 6.9 Steering feel?
Post by: Randys01 on 27 March 2019, 04:45 AM
This is one of my pet grumbles.
I have had everything thrown at my 6.9 front end/steering $$$$ inc the box pulled apart and rebuilt by a Merc specialist who was actually trained in Stuttgart. To do these properly and set up the preload is a tricky job and mine is still damn ordinary.
There is simply too much free play/slop in the centre arc of the box.
My car used to climb a mountain every day for 10 years and I reckon had more steering turns per day than a NY Cab.
The box is worn worn worn.
I understand there is a part in the box which wears and cannot be readily serviced. There is a guy here in Aust who has come up with a tricky mod which resolves this issue markedly I am informed.

By comparison, I have a clapped out 93 W201 that has done 250th Kms and the steering is just delightful. The whole front end is original  and doubtless clapped but it steers and tracks like a peach. The 6.9 on the other hand feels vague..wanders a bit and is hard work positioning the car at speed.
Given the W201 and W116 share similar power steering recirc ball box set ups it suggests to me the box on the W116 must be really shagged.
I reckon 2 inches of freeplay from can see the steering shaft turning into the box and nothing comes out.!

So I bought a rhd 6.9 box out of a very low mileage UK car that rusted away and am saving up to have it fitted.
If this doesn't fix the problem I'll be sure annoyed.

I will report in when the magic day arrives.
Title: Re: 6.9 Steering feel?
Post by: daantjie on 27 March 2019, 07:50 AM
Haha who would have thought this email string would evoke such response ;D!?

I looked some more at my 6.9's setup, US spec of course, and I think I can tell why most of these have not had a proper steering box adjustment.  You can barely see the nut from the top through the gap in the manifold, of course the smog crap is in the way, but even still, the exhaust manifold really buggers up the access.

Option is of course to remove the box from the car (or remove the manifold, hell no :o!?) and do this on the bench, that nut will be so tight, even if you can miraculously get a ring spanner on there in situ, you will likely strip it as the clearance is ultra tight down there.

I guess most wealthy owners would have had this done at shop rates back in the day, so if you find one in the hands of the 5th+ owner, likely this has not been done in a very long time.

Another thing I have wondered about, is how much of the adjusting nut (inner 6mm hex) should be visible, indicating there is still some life left in the adjustment..?  I guess if it appears to be well turned out the box is toasted anyway?  Looks like about 10mm "out" is the max?

Title: Re: 6.9 Steering feel?
Post by: TJ 450 on 27 March 2019, 09:56 PM
Yep, if the adjuster is out about 10mm its probably maxed out.

The W201 has a self adjusting box but is essentially the same, the main culprit is definitely wear in the box. Whether this comes down to a lack of maintenance entirely, I don't know, but the 116 steering boxes are more often than not worn out.

Title: Re: 6.9 Steering feel?
Post by: Randys01 on 27 March 2019, 11:52 PM
General observation
 Nothing on the 6.9's needed any maintainance attention for 100thou  kms. By then they are on the 2nd/3rd owner. The cars are worth 30 % of new. Specialist workshops are at 250 per cent of the hourly rate when the cars were new. Not going near that.!
Tranny oil change and service. nup.
Steering box adjustment in under a 100thou? ?.ha!.
I wish I could be sure of winning the lottery as I am that <10 per cent of 6.9's had their "compensating elements" checked at the 50 km thou mark. Nup.
Oil changes at the extended 15K mark..oooh. I just know that this was extended far too often.

Outcome: hi no of examples with clapped out guides/rockers/cams.
              too many examples with the "waftodrifto" steering box feature

etc. etc

I've never driven a W116 which felt taut trim terrific in the steering dept......the 1st one ..a clean 350se ..I ever drove was 25 years ago and it felt like a fist in a bucket of porridge. It could not have been that worn out? But they must have been OK when new  coz I've never heard/read any grizzles [I can go back to when the Finnie was  new  :-X ].and I've driven  a few other models which were newish/ low mileage at the time and they feel fine.  ...even my aforementioned jaded old W201 gives you a clue.
Title: Re: 6.9 Steering feel?
Post by: TJ 450 on 28 March 2019, 01:11 AM
The other thing that could be a factor is fluid type used, yes given the atrocious history of a lot of cars is the reason. Other models such as the W126, 107s etc also suffer from similar wear as well. I guess I was lucky with mine as I was able to adjust the free play in the centre position out to less than 1”, but the adjuster is most of the way out now.

I have been using a synthetic power steering fluid, and change it every year or so with the later paper filter element.

Title: Re: 6.9 Steering feel?
Post by: daantjie on 28 March 2019, 07:56 AM
The other thing that could be a factor is fluid type used, yes given the atrocious history of a lot of cars is the reason.

Hmmm interesting.  I have clean ATF Dex III in the system, but I guess I should flip this over to full syn PS Fluid ::)
Title: Re: 6.9 Steering feel?
Post by: TJ 450 on 04 April 2019, 07:40 PM
Yes, Kent certainly has his opinion on fluids and he has mentioned ATF vs. P.S. fluids a while back as being a possible cause of leaks and wear issues.

Title: Re: 6.9 Steering feel?
Post by: Mick74 on 22 May 2019, 01:57 PM
A quick update on the 6.9 steering issue. I sourced a second hand box in Germany, from a 1976 6.9, and a new coupler. New fluid and filter as well. I only drove it in traffic, for a short distance, but already, it's a big improvement, with very little play and gives you much more confidence, and I still have to replace the idler arm bushes and front suspension bushes as well (the front wheel moves back under braking!). When all that is done, I'll give another update.