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E320 wagon - Rear suspension riding hard - Suggestions?
Thread Starter
Junior Member
Joined: Apr 2012
Posts: 41
Likes: 0
From: New Orleans , LA.
ML 320 HEAVY METAL EDITION
E320 wagon - Rear suspension riding hard - Suggestions?
99 E320 4matic wagon. 153,000 miles.. rides little hard in the back.
• Over a dip or bump, and it feels like your bouncing hard - almost like a jolt.
Someone asked if its air or i guess spring. Not sure..
How do I tell, and what do i look for?
NO leakage of leveling fluid..or axles... just rides hard over bumps.
My inquiring mind wants to know...
I read somewhere it could be the spring load accumulators?
youtube video here to replace..
• Over a dip or bump, and it feels like your bouncing hard - almost like a jolt.
Someone asked if its air or i guess spring. Not sure..
How do I tell, and what do i look for?
NO leakage of leveling fluid..or axles... just rides hard over bumps.
My inquiring mind wants to know...
I read somewhere it could be the spring load accumulators?
youtube video here to replace..
Last edited by BSR Music; Sep 4, 2012 at 09:03 AM.
MBWorld Fanatic!
Joined: Mar 2006
Posts: 1,627
Likes: 5
From: West Virginia
2001 E320 RWD - Brilliant Silver/Ash: 100,000+
Your accumulators are probably bad but you won't see any fluid leaks. There is a pressurized bladder inside them that ruptures and then the surrounding fluid fills that, all happening internally so there are no external signs.
Newbie
Joined: Sep 2012
Posts: 7
Likes: 1
From: San Francisco east bay
2000 e320
Hi BSR, Musickmann is most correct. Do not change the shocks, just the pressure spheres.
A note on the shocks. Generally speaking the shocks last a really long time, often over 200k mi. If the shocks leak they need to be replaced. If the level valve leaks you may be able to reseal it, if... you can find a kit. otherwise you'd need a new one. You can change the rear ride height by adjusting the length of the link to the valve lever.
Here's what happens when the ride go rough as yours is. 1st a word on how the shocks work. The damper valves are just normal as in a regular shock, but the shaft is quite fat compared to a regular rear shock. Now, think about if you had a dowel inside a soda straw... If you blew on the end of the straw it would push the dowel out...
Ok that is what the level system does. The pump pushes fluid on the end of that fat shaft & pushes the shaft down making the shock extend, thereby raising the rear of the car. Of course the fluid pressure is quite great.
Now, finally to the spheres (also know as pressure resivors). As the car goes over bumps the shock shaft moves up/down. The fluid inside the shock gets displaced & must go somewhere. That where is the pressure spheres. Inside the sphere is a very sturdy rubber diaphram with nitrogen gas behind it. Actually, the entire sphere will be full of nitrogen on a new one. As the fluid is dispaced it goes into the sphere & compresses the nitrogen. The compressed nitrogen does act as a spring somewhat. Mostly it allows the fluid to be stored durning compression over bumps.
Over time nitrogen excapes & the sphere fills with fluid. now you have a hydrualic lock situation when the shock needs to compress.
That is what causes the "jolt" you feel. Over time the sphere can completely fill with fluid & the car will jolt violently & can even cause loss of control.
This is why you may need to add a bit of fluid over time even though there is no leaks. I've changed dozens of these & it always cures the problem.
The factory way of testing these in put on a pressure gauge & start the car. There will be a pressure spike at a certain point & that is the remaining gas level.
However when you feel the jolt it is a sure sign they are bad.
Remember the spheres don't change ride height, just the ride. Ride height is a product of the level valve adjustment. I've noticed over time the rear tends to start sagging a bit. It is not spheres or shocks. My theory is the rubber of the sway bar mounts are sagging a bit changing the effective length of the level valve rod. Adjusting the rod will compensate for that. Keep eye on headlamp aim as you mess with ride height.
Very best, Don
A note on the shocks. Generally speaking the shocks last a really long time, often over 200k mi. If the shocks leak they need to be replaced. If the level valve leaks you may be able to reseal it, if... you can find a kit. otherwise you'd need a new one. You can change the rear ride height by adjusting the length of the link to the valve lever.
Here's what happens when the ride go rough as yours is. 1st a word on how the shocks work. The damper valves are just normal as in a regular shock, but the shaft is quite fat compared to a regular rear shock. Now, think about if you had a dowel inside a soda straw... If you blew on the end of the straw it would push the dowel out...
Ok that is what the level system does. The pump pushes fluid on the end of that fat shaft & pushes the shaft down making the shock extend, thereby raising the rear of the car. Of course the fluid pressure is quite great.
Now, finally to the spheres (also know as pressure resivors). As the car goes over bumps the shock shaft moves up/down. The fluid inside the shock gets displaced & must go somewhere. That where is the pressure spheres. Inside the sphere is a very sturdy rubber diaphram with nitrogen gas behind it. Actually, the entire sphere will be full of nitrogen on a new one. As the fluid is dispaced it goes into the sphere & compresses the nitrogen. The compressed nitrogen does act as a spring somewhat. Mostly it allows the fluid to be stored durning compression over bumps.
Over time nitrogen excapes & the sphere fills with fluid. now you have a hydrualic lock situation when the shock needs to compress.
That is what causes the "jolt" you feel. Over time the sphere can completely fill with fluid & the car will jolt violently & can even cause loss of control.
This is why you may need to add a bit of fluid over time even though there is no leaks. I've changed dozens of these & it always cures the problem.
The factory way of testing these in put on a pressure gauge & start the car. There will be a pressure spike at a certain point & that is the remaining gas level.
However when you feel the jolt it is a sure sign they are bad.
Remember the spheres don't change ride height, just the ride. Ride height is a product of the level valve adjustment. I've noticed over time the rear tends to start sagging a bit. It is not spheres or shocks. My theory is the rubber of the sway bar mounts are sagging a bit changing the effective length of the level valve rod. Adjusting the rod will compensate for that. Keep eye on headlamp aim as you mess with ride height.
Very best, Don
Newbie
Joined: Jan 2013
Posts: 1
Likes: 0
E200 Wagon 1999
Hard riding rear suspension
Hi guys!
Im new to this forum. My E200 1999 wagon experienced same problem like BSR. Hard riding at rear, no sign of absorber leaks, have changed air cell as recommended, but no avail. Any other thought? Thanks in advance.
Im new to this forum. My E200 1999 wagon experienced same problem like BSR. Hard riding at rear, no sign of absorber leaks, have changed air cell as recommended, but no avail. Any other thought? Thanks in advance.
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Thread Starter
Junior Member
Joined: Apr 2012
Posts: 41
Likes: 0
From: New Orleans , LA.
ML 320 HEAVY METAL EDITION
Ainn - what Don has written is accurate. Mine were really bad. They need to be replaced. Simple to do yourself, but save the fluid and re-use. Hope that helps.
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Newbie
Joined: Sep 2012
Posts: 7
Likes: 1
From: San Francisco east bay
2000 e320
Hi Ainn, Hmmm... That is odd. I have a few thoughts. 1st let's review how this works. For the suspension to compress over a bump, the oil in the shock must go into the sphere (air cell). As it does it pushes on a rubber diaphram that has nitrogen gas on the back side. This fluid movement compresses the gas in the sphere. The pressure of the gas acts as an addtional spring. Remember, ride height is obtained by total fluid pressure pressing on the end of the shock shaft.
So... if the car is rough the fluid has nowhere to go or the suspension componets are binding, such as bushings or a binding shock itself. From my experiance in the workshop I've not seen many cases where the bushings or shocks are binding.
On the other hand, if the new spheres were too old, even though new & unused they may have lost their gas. I would have to double check but as I recall the shelf or service life is only 5-7 yrs. Old shelf life spheres can be a real problem as they have lost much or all of pressure. Now that the S & SL class cars made in the earlier 2000s are getting some time on them we are seeing old age failures do to the gas loss. A sure sign of gas loss is you need to add fluid but have no external leaks. This usally happens slowly so not so easy to notice.
Now to testing. The proper way to test is with gauges & watch for pressure spike, which shows gas level in sphere. I you had that equipment you wouldn't need us.
Low pressure would result in low ride height. Still start by making sure fluid level is good. Have some buddies get in the back to weight the car down. Drive the car a while & make sure the level will come up. Level is control by the valve on the sway bar & pump pressure. Spheres cannot control level, but if the level control is not working, it can cause odd things to happen.
Next have a few buddies help bounce the rear of car by pushing on rear bumper/tailgate sill. Get a feel of the bounce & where it gets real stiff.
This part is some work & messy, but remove the lines from the spheres & do the bounce test again. Is it soft now? You want to feel for binding. The ride height will be low, so don't mistake that for binding. If no, your suspenion parts are binding. If yes you are not moving fluid into the spheres. Either the lines have blockage or the spheres are bad, even though new.
Don
So... if the car is rough the fluid has nowhere to go or the suspension componets are binding, such as bushings or a binding shock itself. From my experiance in the workshop I've not seen many cases where the bushings or shocks are binding.
On the other hand, if the new spheres were too old, even though new & unused they may have lost their gas. I would have to double check but as I recall the shelf or service life is only 5-7 yrs. Old shelf life spheres can be a real problem as they have lost much or all of pressure. Now that the S & SL class cars made in the earlier 2000s are getting some time on them we are seeing old age failures do to the gas loss. A sure sign of gas loss is you need to add fluid but have no external leaks. This usally happens slowly so not so easy to notice.
Now to testing. The proper way to test is with gauges & watch for pressure spike, which shows gas level in sphere. I you had that equipment you wouldn't need us.
Low pressure would result in low ride height. Still start by making sure fluid level is good. Have some buddies get in the back to weight the car down. Drive the car a while & make sure the level will come up. Level is control by the valve on the sway bar & pump pressure. Spheres cannot control level, but if the level control is not working, it can cause odd things to happen.
Next have a few buddies help bounce the rear of car by pushing on rear bumper/tailgate sill. Get a feel of the bounce & where it gets real stiff.
This part is some work & messy, but remove the lines from the spheres & do the bounce test again. Is it soft now? You want to feel for binding. The ride height will be low, so don't mistake that for binding. If no, your suspenion parts are binding. If yes you are not moving fluid into the spheres. Either the lines have blockage or the spheres are bad, even though new.
Don
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From: UK
W215 CL500 2005
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Joined: Feb 2011
Posts: 571
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From: Sweden
SL55AMG + SL600 + E320 + A180
Hi BSR, Musickmann is most correct. Do not change the shocks, just the pressure spheres.
A note on the shocks. Generally speaking the shocks last a really long time, often over 200k mi. If the shocks leak they need to be replaced. If the level valve leaks you may be able to reseal it, if... you can find a kit. otherwise you'd need a new one. You can change the rear ride height by adjusting the length of the link to the valve lever.
Here's what happens when the ride go rough as yours is. 1st a word on how the shocks work. The damper valves are just normal as in a regular shock, but the shaft is quite fat compared to a regular rear shock. Now, think about if you had a dowel inside a soda straw... If you blew on the end of the straw it would push the dowel out...
Ok that is what the level system does. The pump pushes fluid on the end of that fat shaft & pushes the shaft down making the shock extend, thereby raising the rear of the car. Of course the fluid pressure is quite great.
Now, finally to the spheres (also know as pressure resivors). As the car goes over bumps the shock shaft moves up/down. The fluid inside the shock gets displaced & must go somewhere. That where is the pressure spheres. Inside the sphere is a very sturdy rubber diaphram with nitrogen gas behind it. Actually, the entire sphere will be full of nitrogen on a new one. As the fluid is dispaced it goes into the sphere & compresses the nitrogen. The compressed nitrogen does act as a spring somewhat. Mostly it allows the fluid to be stored durning compression over bumps.
Over time nitrogen excapes & the sphere fills with fluid. now you have a hydrualic lock situation when the shock needs to compress.
That is what causes the "jolt" you feel. Over time the sphere can completely fill with fluid & the car will jolt violently & can even cause loss of control.
This is why you may need to add a bit of fluid over time even though there is no leaks. I've changed dozens of these & it always cures the problem.
The factory way of testing these in put on a pressure gauge & start the car. There will be a pressure spike at a certain point & that is the remaining gas level.
However when you feel the jolt it is a sure sign they are bad.
Remember the spheres don't change ride height, just the ride. Ride height is a product of the level valve adjustment. I've noticed over time the rear tends to start sagging a bit. It is not spheres or shocks. My theory is the rubber of the sway bar mounts are sagging a bit changing the effective length of the level valve rod. Adjusting the rod will compensate for that. Keep eye on headlamp aim as you mess with ride height.
Very best, Don
A note on the shocks. Generally speaking the shocks last a really long time, often over 200k mi. If the shocks leak they need to be replaced. If the level valve leaks you may be able to reseal it, if... you can find a kit. otherwise you'd need a new one. You can change the rear ride height by adjusting the length of the link to the valve lever.
Here's what happens when the ride go rough as yours is. 1st a word on how the shocks work. The damper valves are just normal as in a regular shock, but the shaft is quite fat compared to a regular rear shock. Now, think about if you had a dowel inside a soda straw... If you blew on the end of the straw it would push the dowel out...
Ok that is what the level system does. The pump pushes fluid on the end of that fat shaft & pushes the shaft down making the shock extend, thereby raising the rear of the car. Of course the fluid pressure is quite great.
Now, finally to the spheres (also know as pressure resivors). As the car goes over bumps the shock shaft moves up/down. The fluid inside the shock gets displaced & must go somewhere. That where is the pressure spheres. Inside the sphere is a very sturdy rubber diaphram with nitrogen gas behind it. Actually, the entire sphere will be full of nitrogen on a new one. As the fluid is dispaced it goes into the sphere & compresses the nitrogen. The compressed nitrogen does act as a spring somewhat. Mostly it allows the fluid to be stored durning compression over bumps.
Over time nitrogen excapes & the sphere fills with fluid. now you have a hydrualic lock situation when the shock needs to compress.
That is what causes the "jolt" you feel. Over time the sphere can completely fill with fluid & the car will jolt violently & can even cause loss of control.
This is why you may need to add a bit of fluid over time even though there is no leaks. I've changed dozens of these & it always cures the problem.
The factory way of testing these in put on a pressure gauge & start the car. There will be a pressure spike at a certain point & that is the remaining gas level.
However when you feel the jolt it is a sure sign they are bad.
Remember the spheres don't change ride height, just the ride. Ride height is a product of the level valve adjustment. I've noticed over time the rear tends to start sagging a bit. It is not spheres or shocks. My theory is the rubber of the sway bar mounts are sagging a bit changing the effective length of the level valve rod. Adjusting the rod will compensate for that. Keep eye on headlamp aim as you mess with ride height.
Very best, Don
I just bought a E320 4matic from 1999 with 180K miles on it - it is fairly good condition but needs to have a good work-over for wearing parts and I'm making a list .... a long list for which I'm confident will give this car many more miles ......
Now to my question - driving the car is hard since it's stiff like a board - going over bumps makes it jump and by appearance the car looks very high - normal springs only in the front - springs and hydraulic shocks in the back .... cluster saying "fill hydraulic oil" .... so it has all the signs of the above "spheres" fault. The previous owner said it started when his back wheel exploded while driving ..... but that does not have to be connected to the suspension going bad.
Correct me if I am wrong - In EPC it is called a "AIR RESERVOIR (SPRING LOAD ACCUMULATOR)" - theres two of them ...... pic. included - part A1403280515
.... but could the "HEIGHT CONTROL VALVE" not be involved? ... if this fail and somehow raises the car fully - won't it have the same symptoms?
Looking at the pics. hydraulic springs are a little "wet" on the bottom - they could be bad too but it can also come from the leaking trans. ....
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Joined: Jan 2022
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2000 E320 4matic wagon
I had replaced the accumulators, but the ride is still high and harsh. This morning I disconnected the linkage at the SLS valve and stroked it up and down with the engine idling and got no response out of the valve. The rear level did not move, it seems to be stuck fully extended; so I am assuming the SLS valve has failed. Is there anything else to try before I replace the SLS valve? The back story here is that the car has been out of service for the last two years. In that time a hydraulic line to the SLS had broken so a friend replaced the line to the SLS valve and accumulators. I replaced the accumulators at this time. The back end became very high and stiff. So I don't know if we broke the valve or if it had failed before all these problems. Also, since the ride is still really stiff the new accumulators might be defective. I can replace these under warrenty. Has anyone had this problem before?
