Rear Springs
 

Good afternoon, I own a 1989 420 SEL and need to replace the rear springs,only because teh left rear seems to be sagging, I'm a bit confused, upon lookinb and pricing the springs they make mentin of different size shims What,m if any size do I replace??? Why? Should I replace with same OEM shims ??
I am also going to replace all four shocks, cars has 117600 miles, rides OK but corners sloppy. Any help would be appreciared. Thanks in advanced,

Tim

The shims you refer to are spring pads. These pads are designed to ensure that each vehicle has the correct ride height irrespective of options etc. Unless you want to alter the height of the car then I would replace the pads with the same size that is currently fitted. Once you have the new springs fitted you may want to change the pads to a smaller/higher to acheive the correct look. Shock replacement is very easy on these cars.

Matt.

Just one quick question, does your SEL have regular shocks or does it have hydropneumatic skocks? If your car has the self-leveling rear suspension, changing out the shocks isn't going to be cheap or as easy as reg. shocks.

There is no difference in the shocks, the self levelling cars have different springs and also have accumulators which provide the levelling function.

Matt.

Of course there is a difference in the shocks. Just look at shocks for a wagon, they are $200+ a piece. On cars with self leveling systems, there is a hyd. line that goes to the top of each rear shock. What do you think the hydraulic fluid is for? The accumulators (nitrogen cells) are what pressurize the hydraulic fluid that goes to each shock to raise and lower it.

Thanks for all the info, what you're telling me is that the shims should or shoule not be replaced??? I have regular suspension not level ride. Thanks again,
Tim

I replaced the rear springs on my 300D a few years ago and adjusted the rear end height using spring pads with different thicknesses. You should replace the rubber shims/spring pads if they are damaged. As Mattman wrote, the pads are used to correct the height of the rear end using pads of different thicknesses (as well as cushion for the spring to body contact area). When replacing the springs take a note of the part number on the spring pads (if it can still be seen) and measure the thickness of the rubber on the top portion of the pad in a place where the spring did not make contact. The adjustment is done after you replace the springs using the old spring pads with shocks installed and put the full weight of the car back on the ground (a drive around the block will help to let the suspension settle into its working position). Then, on a flat surface, look at the rear of the car to see if it is level or not with an empty trunk and, as I recall from the M-B manual, a half full or so tank of fuel. If the rear end is level looking at it from the trunk end facing forward, then no adjustment is needed. If the rear end is not level, then you need to buy and install pads that will level the rear end. This may take replacing one or both pads to achieve a level rear end. On a flat surface measure the difference in height from one side of the rear end to the other to help determine the pad(s) that you need.

Good Luck!
Tom

I thought that the accumulators provided the ride height adjustments, are these basically just reservoirs for the shocks then? When people say the accumulators go bad how does this affect the ride quality? How many miles are the shocks and accumulators good for normally?

Cheers
Matt.

Mattman, the accumulators do play into the ride height, in that they keep the correct pressure/fluid in each rear shock. There is a level controller attached to the rear sway bar, that senses when the backend has been pushed down. When these accumulators lose pressure the ride becomes both bouncing and hard. Half of the accumulator has fluid the other side has nitrogen gas. When the gas leaks past the internal seal, the hyd. fluid fills in the other half of the accumulator. At least on the TDs the cells are about the size of a softball.

Thanks Rick, I see the accumulators aren't that expensive. I have heard of a few people replacing the levelling valve - have you any experience with that?

Cheers
Matt.

No. I haven't messed with my system yet. I have read up on it in both the Haynes manual and of course, the MB chassis manual. I am suspecting that my accumulators are shot. When I put the car in reverse the backend bounces, whereas my SD just raises. This is my first car that has a self leveling system, so I am in the learning curve right now.