Date registered: Jan 2012
Vehicle: 2002 ML320; 2006 S350;2016 GLC 300
Location: Vero Beach, FL
Mentioned: 1 Post(s)
Quoted: 42 Post(s)
I noticed that the write-ups I have seen on accumulators do not address the hydraulic fluid replacement procedures. Here are the steps I used a few weeks ago on my car which includes depressurizing (bleeding) the rear-end hydraulic leveling system, replacing the accumulators, replacing the hydraulic fluid, and rear suspension operation check. I added some notes along the way that may help you. These steps came from the WIS documents which I have attached. My understanding is that when you replace the accumulators, you must replace both at the same time.
1) Put rear of wagon on jack stands (not stated specifically in WIS, but I wouldn't be able to get the accumulators off easily any other way).
2) Remove rear tires
3) Detach the link rod on the level control lever. Best position to access this is on the passenger side rear wheel well.
4) Open the level controller oil drain screw (I think I used an 11mm box wrench). Drain the fluid out. Close the drain screw. Notes: The drain screw was very tight and I needed to spray WD40 and waited 15 minutes before being able to loosen the drain screw. I used a 1/4" ID tube and put a bucket underneath to catch the fluid. Probably took about 30 minutes to drain the fluid. I drained almost exactly 1 liter of fluid.
5) Removed passenger side accumulator and installed new accumulator. Others have posted plenty of documentation on this. But here is what I did: First, put a bucket underneath the accumulator. No need for a drain tube. Unscrew large fitting first and let it drain, then unscrew the small fitting and let it drain. Fluid will drain out for a less than a minute, if that. Then disconnect the three bolts that hold the accumulator in place. Take off the accumulator. Install the new accumulator reversing the above sequence.
6) remove driver's side accumulator and install new accumulator. Same procedure as above.
7) syphon all the hydraulic fluid out of the reservoir which is located in the engine compartment. I used a simple $3 disposable syphon hand pump and drained it into a bucket. Fill the reservoir with new fluid to max line. I used Fuchs Titan ZH 5364B.
8) Replace hydraulic fluid filter with new filter. It is located on the reservoir cap. This is a total PITA process. This process is documented in the stickies. Make sure you tighten the reservoir cap when finished!
9) set level controller lever to "F" position
10) start engine. Keep it in park! Run engine for 60 seconds at 2500rpm. Turn engine off. Notes: During that time, the fluid reservoir drops quite a bit and you will hear a very loud whistling/whining noise coming from the rear end. This is normal. Do not add any fluid to the reservoir during this process. Just make sure the fluid level doesn't drop too far so that the pump sucks in air (If you started with the fluid at the max line, I don't see this happening). The level controller in the "F" position allows the fluid to fill the rear struts. This causes the rear end to rise. This fluid comes from the reservoir causing the reservoir level to drop. That is why the reservoir is so large.
11) set the level controller lever to "L" position for 60 seconds. Once you move the controller level to the "L" position, you will hear the fluid draining out of the rear struts. If you check the reservoir during this time, you will see the fluid level rise.
12) Well after the 60 seconds required in the "L" position, I secured the link rod on the level control lever. I noticed that the position of the lever stayed basically in the "L" position.
13) Put the wheels back on and take the car off the jack stands.
14) Open the wagon hatch and bounce up and down on the rear end about 10 times.
15) Check fluid level in the reservoir and fill to "max" line, if needed.
16) Measure the height of the rear on both sides. I measured 27 3/8" on drivers side and 27 5/8" on passenger side. Height measured from ground to top of wheel well.
17) I started car and drove it several miles to Lowes. No problems.
18) I folded down the back seats and filled the cargo area with about 500lbs of bagged top soil and peat moss. I drove home and measured the rear height. It was about 26 3/4", if I remember correctly. So, that seems to work.
I can't say for sure how much new fluid I added to the system. I think somewhere around 2.5 liters. The reason I don't know is that I screwed up a few times during this process and fluid sprayed all over the engine compartment. I also added fluid while the level was going down during the "F" position and it drained back out of the reservoir when the lever was put back in the "L" position.
There are several additional things you can do that I didn't. For example, the hydraulic fluid supports the power steering. AMG posted a nice DIY on the p/s fluid replacement where he moved the steering wheel back/forth several times. I didn't do that.
I hope this helps someone in the future. Good luck.
Last edited by todd_raleigh; 11-05-2013 at 09:17 AM.