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1991 560 SEC
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Discussion Starter #1
Hello. I am slightly stumped on this one and could use a bit of help. I just replaced 2 front tires on my 85 500 SEC. When the guy changed the tires, he noticed a bent tie rod. As a result, I just changed both tie rods and took it up the street to get it aligned at the tire shop. They told me that they could not do it because it looks like the ride height is higher in the front than in the rear. Now that I look at it, it does sit a little higher in the front, but the only thing that was done was new tires and the tie rods I put on. Could any of that have caused it to raise in the front? Should I just take it somewhere else and let them align it and disregard what the tire shop said about the height? Any help would be greatly appreciated ......

Thanks

John.
 

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1990 SEC
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John,

The new tires and tie rods probably did nothing to the car. You just have discovered that the rear end sags a bit from worn out bushings and tired springs.

How many miles on the car?

Rebuilding the rear suspension is going to be expensive. While you're in there you might as well look at replacing you stock springs with some H&R sport springs.
 

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1991 560 SEC
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Discussion Starter #3
The car has 150K miles on it. I thought about replacing all the springs on it, and still may do it. Would you suggest I just have them align it the way it sits right now? It should drive better than it does right now. Since I put the new tie rods on, you can tell it doesn't track exactly right and I don't want to drive it too far like that.
 

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1990 SEC
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Yes, I would recommend that you have the alignment done.

The cost is about $100, but not doing it will be more expenive in tire and component wear.
 

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1993 300TE, 1995 E320 Wagon
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John--

A rear-end height difference should not be a reason to cancel a front-end alignment, unless it's an extreme case. Sounds like BS to me from the tire/alignment place (maybe they don't know how to do it on an older car). Ask your trusty independent mechanic where he would take the car for an alignment. These cars are sensitive to proper alignment, and doing it is key to the fine handling we've all come to love and expect in these cars.

I think you have the SLS system in the SEC (you definitively have it in the SEL)... and if so, some height adjustment can be made by adjusting the rod that controls the valve at the rear. An easy DIY with a couple of 10mm (9mm??) wrenches. Do a search on Self Leveling Adjustment, and you're likely to find out whether it's lengthen the rod or shorten it (I can't remember). My front end does look higher than the rear from the clearance of the wheel wells, but the car rides level by reference to the sills under the doors. The fact that your (car's) rear end sags a bit is an indication of (A) an out-of-adjustment SLS, (B) worn springs (maybe), (C) worn rear subframe bushings (likely), (D) worn differential mount (also likely), or (E) faulty nitrogen cells (accumulators). In the latter case, your ride would be hard/bouncy, and if it isn't, it would probably eliminate the cells as a cause of the sag. Check the level of the hydraulic oil in the reservoir in the engine bay too.

I would definitely go with the subframe bushings and diff. mount first, as these are relatively inexpensive (like $50, total), and DIY-able in an hour or two. If you do decide to redo the springs, I would definitely go with H&Rs, and get Bilstein HD shocks for the front (figure $450 in parts). This upgrade represents a vast improvement in handling, with a little sacrifice in terms of ride harshness, from what I've read. If the rear hydraulics are OK (and you'd know it if they were leaking), I'd keep the stock system with the H&R upgrade. New accumulators are about $100 a side, while the hydraulic rams are very spendy ($800 each???), but rarely fail. You can ask Jonathan (member jhodg5ck) about his recommendations too.

Best--

Dave
 

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1990 SEC
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I think you have the SLS system in the SEC (you definitively have it in the SEL)... and if so, some height adjustment can be made by adjusting the rod that controls the valve at the rear. An easy DIY with a couple of 10mm (9mm??) wrenches. Do a search on Self Leveling Adjustment, and you're likely to find out whether it's lengthen the rod or shorten it (I can't remember). My front end does look higher than the rear from the clearance of the wheel wells, but the car rides level by reference to the sills under the doors. The fact that your (car's) rear end sags a bit is an indication of (A) an out-of-adjustment SLS, (B) worn springs (maybe), (C) worn rear subframe bushings (likely), (D) worn differential mount (also likely), or (E) faulty nitrogen cells (accumulators). In the latter case, your ride would be hard/bouncy, and if it isn't, it would probably eliminate the cells as a cause of the sag. Check the
Dave,

At rest, without the engine running, doesn't the car rest fully on the springs and bushings?

If that is the case, and the rear end sags, doesn't that indicate the problem lies with the springs and/or bushings, and not the SLS?
 

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1993 300TE, 1995 E320 Wagon
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AxelWulff--

I don't think that the car necessarily does just "sit on it's springs" when at rest/not running. I may be wrong here, and someone please correct me if I am, but in my case, I raised the car height about an inch or so last spring using the hydraulic system, as per the manual. The car does not settle down any after turning it off, nor is it down in the morning when I start her up again. This leads me to believe that the control valve is also a "check valve" in that it lets pressurized oil into the accumulators when the rear end is low (raising it), and will only let it out again when the load is released. The result would be that the system remains pressurized (at a reasonable pressure I assume), and hence the car's height remains constant, with some of the weight supported by the hydraulics. I am unfamiliar with the schematics of the system however, and this would be a moot point if the accumulators had a simple return line (no check valve) to the reservoir-- but then how would the system maintain any pressure at all when "carrying" a load?

There are some on the forum who wrote that this would cause undue strain on the accumulator membrane (and subsequent premature failure), but I felt it to be a worthwhile experiment to try and raise the rear end a bit. My reasoning was that the membranes surely take a hell of a lot more stress when operating under load, supporting a 2+ ton car over bumps and dips. And Mercedes engineers certainly wouldn't have put in a system that was prone to failure due to "normal" (i.e. four people plus luggage) loading. I also knew that my rear subframe bushings and differential mount were relatively new, so the only other alternative was new springs.

It has been about a year and 7000 miles since I did the adjustment, and everything is working fine. That being said, I would love to put in H&Rs all around, and Bilstein HDs on the fronts, with new spring shims. Can't afford to, though.

Best-

D
 

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1990 SEC
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AxelWulff--

I don't think that the car necessarily does just "sit on it's springs" when at rest/not running. I may be wrong here, and someone please correct me if I am, but in my case, I raised the car height about an inch or so last spring using the hydraulic system, as per the manual. The car does not settle down any after turning it off, nor is it down in the morning when I start her up again.
Dave,

You're absolutely right. You've increased the ride heigth on your car by adjusting the check valve lever and Satish did the same thing on my car, dialing in an agressive-looking rake.

I must have been thinking about the French Citroens. :eek:
The old Citroen DS's fall to the ground when the engine is turned off.
 

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1991 560 SEC
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Discussion Starter #9
My SEC is an 85. It doesn't have SLS. I'm going to take it to another alignment shop and see what they tell me today. Either way, I'm just going to have them align it. Would anything else cause the front end to sit higher? I understand that there may be some shims in the front springs that can be removed to level it out with the rear?
 

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AxelWulff--

I raised the car height about an inch or so last spring using the hydraulic system

D
Did you do this by changing the length of the rod itself, or did you loosen the nuts on the clamp at the sway bar and adjust that clamp itself?
 

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1993 300TE, 1995 E320 Wagon
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My SEC is an 85. It doesn't have SLS. I'm going to take it to another alignment shop and see what they tell me today. Either way, I'm just going to have them align it. Would anything else cause the front end to sit higher? I understand that there may be some shims in the front springs that can be removed to level it out with the rear?
mr_gm123--

A couple of questions:

1. How does the car handle as it is? If it dives/wallows an corners, then you're going to want to look into replacing all four shocks, as well as subframe bushings, on top of the alignment issue.

2. What is the difference in height between the front and rear, as measured at the sills? Don't go by the appearance of the wheel well clearance, as the front is going to have about 2 more inches than the rear.

If the car really is squatting in the rear (not uncommon), and since your SEC doesn't have SLS, the reasons for a front high/rear low posture are limited to the remaining parts from my list:

(B) worn springs (maybe), (C) worn rear subframe bushings (likely), (D) worn differential mount (also likely).

The shims at the top of the springs are part of the equation too, but it's unlikely that there's a difference between front and rear wear, so they're not likely the issue. Taking the shims out of the front would indeed lower the front, but you would want new shims (just thinner ones) as they are there for a reason. Replacing the shims also means removing the springs, and at that point, I'd be putting in H&Rs. When you go to the new alignment shop, ask them what they would charge to replace the rear subframe bushings and diff. mount, as this is most likely the issue.

Good luck at the shop today!

D
 

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Did you do this by changing the length of the rod itself, or did you loosen the nuts on the clamp at the sway bar and adjust that clamp itself?
Markus--

The adjustment is to the rod itself, not to the clamp. I vaguely remember having to remove one end, loosen a locking nut, then lengthen/shorten the rod. Reverse procedure to put it back together. If you go under the car and have someone sit on the lip of the trunk while watching how the swaybar and lever interact, you can figure out how the lever works, and act accordingly. I'm dimly recalling shortening the rod by a couple of turns to raise the rear end.

If you manage to find success, perhaps we can make this into a DIY sticky.

Good luck--

Dave
 
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