Great post Peter - will add this to the stickies when i get it up
get the fluid from Phoenix lubricants in oz - it is $26 a litre for Pentosin CHF11s
get the fluid from Phoenix lubricants in oz - it is $26 a litre for Pentosin CHF11s
ABC: Change the front and rear pressure reservoirs
After replacing the ABC pump on my 2003 SL55 (134,000km) a few months ago I kept getting intermittent white ABC warnings, particularly after going around a corner with a bump slowly or after hard acceleration. For a while now the ride has seemed a bit hard and not like the magic carpet it used to be.
I decided to replace the pressure reservoirs. The best local price was $584 each (I didn't bother asking the dealer) The cheapest price was on parts.com but they don't ship to Australia. I ended up buying two from pelicanparts.com for $580 shipped
The reservoirs are located in front of the front and rear wheel behind the plastic wheelarch shrouds.
The procedure is sort of similar for both ends, I started at the back.
Chock the wheels, handbrake on, jack up the car and use a secondary support
Remove numerous plastic clips and nuts that secure the wheel arch shroud and gently pry it out... it's tricky
While holding a tin under the bleed screw crack it and you will collect about 150ml of fluid
I was dismayed at just how black and opaque the fluid was after I had flushed it with 4 litres of fresh stuff about a year ago ( yes I know I should have used more; the manual says 10)
Remove the nut securing the assembly (indicated in the photo) and the pipe clamp (in another photo) and gently pull it out to the rear and down as far as the pipes and hoses will allow.
Loosen the pipe nut with a 17mm spanner then remove the three nuts securing the reservoir.
Undo and pull out the pipe being careful not to let any dirt enter and remove the reservoir
Assembly is just the reverse, getting the nut on the pipe clamp is tricky
The front starts out the same. Only remove the front wheel arch plastic shroud
Loosen the bleed screw and catch the fluid that comes out; about 100ml is all I got
The valve/ reservoir assembly does not appear to come out easily so you must undo the pipe nut first then remove the three nuts that hold the reservoir in place. The two outer ones are OK, the inner one will need an extension on your 1/4" drive socket and you will need to stick your head under to see the little devil
Assembly is just the reverse but the car will be very low when you lower the jack
I had only bought 4 litres of ABC oil, not intending to do a total flush.
I syphoned out all of the oil in the reservoir then filled it up with fresh stuff running a hose from the return line down into bottles so I could gauge how much was being used
When I started the car it took a while to lift and the fluid level dropped pretty smartly.
After it had run for a few minutes and I topped the fluid level up the returning fluid was transparent and looked clean.
Unfortunately I only had another litre of fluid left and one rodeo cycle went through that pretty smartly.
The oil in the reservoir is certainly much cleaner but I have ordered another 8 litres and a filter and will do the job properly
The ABC fluid in Australia is prohibitively expensive with the dealer charging $90 per litre and Silverstar spares wanting about $60
When I contacted MB spares in the ACT they quoted $30 something per litre and I questioned that they were supplying the right part. When it arrived it was SWAG brand Power Steering Fluid and their website lists it as the same specification as the original Pentosin
The removal and replacement of the reservoirs took about an hour each and you could probably do it in half that time if the trim wasn't so difficult to remove and replace
It was a straightforward job and the car rides beautifully again with no warnings
I decided to replace the pressure reservoirs. The best local price was $584 each (I didn't bother asking the dealer) The cheapest price was on parts.com but they don't ship to Australia. I ended up buying two from pelicanparts.com for $580 shipped
The reservoirs are located in front of the front and rear wheel behind the plastic wheelarch shrouds.
The procedure is sort of similar for both ends, I started at the back.
Chock the wheels, handbrake on, jack up the car and use a secondary support
Remove numerous plastic clips and nuts that secure the wheel arch shroud and gently pry it out... it's tricky
While holding a tin under the bleed screw crack it and you will collect about 150ml of fluid
I was dismayed at just how black and opaque the fluid was after I had flushed it with 4 litres of fresh stuff about a year ago ( yes I know I should have used more; the manual says 10)
Remove the nut securing the assembly (indicated in the photo) and the pipe clamp (in another photo) and gently pull it out to the rear and down as far as the pipes and hoses will allow.
Loosen the pipe nut with a 17mm spanner then remove the three nuts securing the reservoir.
Undo and pull out the pipe being careful not to let any dirt enter and remove the reservoir
Assembly is just the reverse, getting the nut on the pipe clamp is tricky
The front starts out the same. Only remove the front wheel arch plastic shroud
Loosen the bleed screw and catch the fluid that comes out; about 100ml is all I got
The valve/ reservoir assembly does not appear to come out easily so you must undo the pipe nut first then remove the three nuts that hold the reservoir in place. The two outer ones are OK, the inner one will need an extension on your 1/4" drive socket and you will need to stick your head under to see the little devil
Assembly is just the reverse but the car will be very low when you lower the jack
I had only bought 4 litres of ABC oil, not intending to do a total flush.
I syphoned out all of the oil in the reservoir then filled it up with fresh stuff running a hose from the return line down into bottles so I could gauge how much was being used
When I started the car it took a while to lift and the fluid level dropped pretty smartly.
After it had run for a few minutes and I topped the fluid level up the returning fluid was transparent and looked clean.
Unfortunately I only had another litre of fluid left and one rodeo cycle went through that pretty smartly.
The oil in the reservoir is certainly much cleaner but I have ordered another 8 litres and a filter and will do the job properly
The ABC fluid in Australia is prohibitively expensive with the dealer charging $90 per litre and Silverstar spares wanting about $60
When I contacted MB spares in the ACT they quoted $30 something per litre and I questioned that they were supplying the right part. When it arrived it was SWAG brand Power Steering Fluid and their website lists it as the same specification as the original Pentosin
The removal and replacement of the reservoirs took about an hour each and you could probably do it in half that time if the trim wasn't so difficult to remove and replace
It was a straightforward job and the car rides beautifully again with no warnings
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1 - 20 of 37 Posts
What's inside the pressure reservoirs
I was curious to find out why the reservoirs fail
I followed the procedures in the WIS to evacuate the reservoir of pressure for disposal
Don't tamper with the reservoir unless you have done this. The gas inside is under very high pressure and will do yourself serious damage.
I cut the reservoir in half and the photos show the story
There was a full charge of gas inside the reservoir and no oil escaped the evacuation hole so the diaphragm was still patent... no holes
The diaphragm had a number of "bubbles" or "aneurysms" that were full of gas so I assume that the rubber had deteriorated and delaminated. You can see these in the photos
The diaphragm was fairly hard and I am assuming that this was why they fail to absorb the shocks anymore.
Since replacing them a few weeks ago the ride is back to magic carpet and no more ABC messages
Peter
I was curious to find out why the reservoirs fail
I followed the procedures in the WIS to evacuate the reservoir of pressure for disposal
Don't tamper with the reservoir unless you have done this. The gas inside is under very high pressure and will do yourself serious damage.
I cut the reservoir in half and the photos show the story
There was a full charge of gas inside the reservoir and no oil escaped the evacuation hole so the diaphragm was still patent... no holes
The diaphragm had a number of "bubbles" or "aneurysms" that were full of gas so I assume that the rubber had deteriorated and delaminated. You can see these in the photos
The diaphragm was fairly hard and I am assuming that this was why they fail to absorb the shocks anymore.
Since replacing them a few weeks ago the ride is back to magic carpet and no more ABC messages
Peter
Attachments
6
So responding to my own post, here is what I did to replace the front accumulator on my 2008 SL550. Note the usual disclaimer about this just being a report of what I did and not a recommendation.
I believe that this is a different configuration to the SL500. I removed the front left wheel bay shrouds to gain access to the accumulator. It is hidden behind the valve block. I didn't want to remove the whole valve block assembly as recommended by WIS, so I worked to get enough room to get a wrench on the accumulator.
Release the hose clamps to allow the hydraulic hoses to move.
I then removed the lower mount plate by undoing the mounting nuts (there might be one more than shown). The mount plate is a two piece assembly (see pic below). Once the nuts are off, it is held in place by the 3 vibration mounts. I gently pried the mount rubbers over the 3 mount pins to release it. It wouldn't come out completely as the hoses trapped it. I was able to gently pry it apart enough to reach in and undo the 2 bolts that attach the upper plate half to the valve body. Once free the mount assembly could be removed and I now had access to get a very slim wrench in to unscrew the accumulator. I had not run the car in a while, so all the pressure had already dissipated and I only had a couple of cc's of fluid drain out.
I did the reverse to put it back together. Ran the car and adjusted the level a dozen times or so to bleed. Took it for a test run and all seems to be fine. I am not seeing a difference in ride as I did this as a preventative measure as the car now has about 65 thousand miles on it.
Hope this helps.
3
So moving to the rear accumulator on my 2008 SL550, which also has a different set up to the SL500.
2 hydraulic hoses are hard mounted and 2 have quick disconnects.
Sometimes you just have to swallow your pride - how do I use the quick disconnect tools? I am sure it is easy, but for some reason I am not working it out...
Also, I want to replace the hose connector seals and backup rings. Hopefully MB will sell them separately or else I will need to get a McMaster backup number.
2 hydraulic hoses are hard mounted and 2 have quick disconnects.
Sometimes you just have to swallow your pride - how do I use the quick disconnect tools? I am sure it is easy, but for some reason I am not working it out...
Also, I want to replace the hose connector seals and backup rings. Hopefully MB will sell them separately or else I will need to get a McMaster backup number.
2
So to again answer my own question. The disconnect tools go either side of the fitting with legs facing down. Pushing them in from either side makes them wedge against the other which pushes the sleeve up to disconnect. You do the same to reconnect; pull the 2 hose halfs to make sure that they connected properly.
Release the hose clamp as in the original SL500 write up. Remove the upper lateral vibration mount. Slide the whole assembly out. I was able to rotate it so I didn't have to disconnect the electrical plugs. Access to the accumulator was finally "easy".
Once it was all back together, I bled out through the bleed nipple to clear out any old trapped hydraulic oil. Checked for leaks and wrapped it all up. I will continue to check for signs of leakage under the car for a couple of weeks just in case.
Hopefully this will all help fellow SL550 owners as the front and rear access layouts are different.
Release the hose clamp as in the original SL500 write up. Remove the upper lateral vibration mount. Slide the whole assembly out. I was able to rotate it so I didn't have to disconnect the electrical plugs. Access to the accumulator was finally "easy".
Once it was all back together, I bled out through the bleed nipple to clear out any old trapped hydraulic oil. Checked for leaks and wrapped it all up. I will continue to check for signs of leakage under the car for a couple of weeks just in case.
Hopefully this will all help fellow SL550 owners as the front and rear access layouts are different.
2
I can't remember exactly how I got that front accumulator out. I know that it is almost forced in there. You just have to wiggle and pull on it until you can free and clear the two bolts on the accumulator. I knew that when it came time to reassembly the accumulator, that I was going have a hard time getting it back onto the two rear bolts. I made a few attempts to get it put back in but it was such a struggle and I was afraid that I was going to bend or deform something. So what I did was slotted the two bolt holes. After that, it went back together like a breeze. I slotted the rear accumulator too. Those accumulators are held in with 3 bolts and also the pressure line itself keeps it in place. Can't go anywhere.
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Good luck,
Bob
Good luck,
Bob
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