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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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Discussion Starter #1
Every now and then as I am driving down the road the rear end starts bouncing. I assume it has to do with my rear suspension. I have checked the fluid and topped it off. It was only slightly down. I am using the correct mineral oil and there are no leaks while it sits overnite. What should I look for and what mite need fixing? Thank you.
 

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1985 300CD
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2,137 Posts
It sounds like you need new accumulators. Your rear end is bouncing on the springs since the accumulators aren't doing their job anymore.
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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647 Posts
X2 on the accumulators. Common wear item on the wagons. Not likely the struts, even if they are leaking some.

You can check them by undoing the line and poking the eraser end of a pencil into them. If there is resistance within a couple of inches or so, they are probably OK. If the pencil goes all the way in, the bladder in the accumulator has failed.

About $250 for both accumulators and an afternoon under the car will get your ride back to where it belongs.
 

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I have a 84 300td sedan with a similar problem but mine only shows itself after about 30 miles of highway driving. It happens twice a day generally after 30 miles of 60 - 70mph of highway driving. If I pull over for a few minutes it has gone away in the past. This morning it went away but immediately came back after a few minutes at 60mph. It is a mechanical sound in time with the drive train speed. The noise and vibration continued this morning even at slow speeds. Any suggestions?
 

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1967 250 SL, 1965 300SE lang
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3,063 Posts
I have a 84 300td sedan with a similar problem but mine only shows itself after about 30 miles of highway driving. It happens twice a day generally after 30 miles of 60 - 70mph of highway driving. If I pull over for a few minutes it has gone away in the past. This morning it went away but immediately came back after a few minutes at 60mph. It is a mechanical sound in time with the drive train speed. The noise and vibration continued this morning even at slow speeds. Any suggestions?
Unless your sedan has self-leveling suspension like the wagon, none of the advice in this thread is relevant to your car. The wagons have a hydraulic rear suspension. The sedans (at least in the US) don't.
 

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1985 300CD
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I have a 84 300td sedan with a similar problem but mine only shows itself after about 30 miles of highway driving. It happens twice a day generally after 30 miles of 60 - 70mph of highway driving. If I pull over for a few minutes it has gone away in the past. This morning it went away but immediately came back after a few minutes at 60mph. It is a mechanical sound in time with the drive train speed. The noise and vibration continued this morning even at slow speeds. Any suggestions?
Check your flex discs. If there are any cracks, replace them.
 

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1967 250 SL, 1965 300SE lang
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3,063 Posts
Back to original question...

If you can park the car and with the motor turned off jump up and down on the rear bumper and the car bounces, then there is something seriously wrong with your rear struts.

If while driving you go over a speed bump and the rear suspension WAY over-reacts and bounces real hard, it's one or both of the accumulators.

Have you verified that your self leveling suspension (SLS) works? Load up rear end of car with 400+ pounds, car sinks down some, start car, car should move back up to starting point....
 

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Back to original question...

If you can park the car and with the motor turned off jump up and down on the rear bumper and the car bounces, then there is something seriously wrong with your rear struts.

If while driving you go over a speed bump and the rear suspension WAY over-reacts and bounces real hard, it's one or both of the accumulators.

Have you verified that your self leveling suspension (SLS) works? Load up rear end of car with 400+ pounds, car sinks down some, start car, car should move back up to starting point....
I've tried bouncing the rear bumper 3 or 4 times but it immediately stops when I let go. I don't have a SLS. Yes, when I go over a dip in the road it will sink low but recover ok.
 

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1967 250 SL, 1965 300SE lang
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I've tried bouncing the rear bumper 3 or 4 times but it immediately stops when I let go. I don't have a SLS. Yes, when I go over a dip in the road it will sink low but recover ok.
The original thread is about a wagon and the rear SLS. Start a different thread about your rear suspension - they are not related topics.
 

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1982 300td wagon with 435,000 sold, 1984 300sd 230,000, 1980 300sd 113,000, 1983 300cd 260,000
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158 Posts
Discussion Starter #11
I am going to try and fix this myself as every time I go to a mercedes mechanic I get taken. I guess the guru in Washngton will be my best bet on parts. Thank you all for narrowing the problem down.
 

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1981 300TD 360k--1966 230 165k--1970 280se 172k
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647 Posts
Not too hard of a job. The lines can be difficult to break loose. I had to use the hot wrench (propane torch) to free mine up. Consider rebuilding the valve while you are under there. A guy here on the forum (Andrew) sells a cheap O ring kit. Do a search for all the details.

New accumulators made a world of difference on my wagon.
 

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1967 250 SL, 1965 300SE lang
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3,063 Posts
If your valve is leaking then rebuilding it makes sense. If it isn't then I don't see much point (but the o-ring kit is great). The problem is that some valves have external corrosion and getting the fittings off is very difficult. If there is nothing wrong with the SLS valve then I wouldn't mess with it. As for best place to buy the accumulators, I bought mine from autohausaz dot com -- free shipping, no sales tax, great price.
 
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