How to - ABC Fluid flush and filter

[alexanderfoti]

I recently had issues with the front of my c215 dropping after being parked. Assuming a piece of crud in the front valve block, I decided to carry out an ABC Fluid change and filter.

The fluid was black instead of green, and didn't smell too hot. If the filter does not work, I will be removing the front valve block and replacing o-rings and cleaning it up.

Mercedes WIS states, if the car drops, to filter the ABC fluid. I decided to do a flush as well.

Flush first, then filter with the new fluid, as the flushing process a lot of crud from the system. At no point must the system ingest air, or you will damage the ABC pump

You will need, 6+ liters of Pentosin CHF11S. I bought mine from Germany at about half the price of a uk dealer. You will also need 2 x of the new ABC filters, part no A 003 184 61 01, and a length of 1/2 inch hose with a straight adapter on the end. (don't get a barbed one like mine, as I had to cut the hose off to remove the OEM pipe!









Step 1:*

Start the car and carry out a rodeo for 15 minutes. This warms the fluid up and allows all the bits to get out of the system.




Assuming you do not have access to STAR, you can drive the car around on some bumpy roads whilst cycling the height adjustment button a lot. This wont be 100% but it will carry out the same function.

Step 2:

Ensure the top of the ABC*reservoir*is 100% clean as possible

Turn engine off, remove the return hose from the ABC reservoir, and attach it to your length of pipe:





Direct the pipe into a suitable bucket (at least 10 liters to be safe). WIS says to top up the system through the dipstick hole, but I chose to use the gaping hole that the filter would have sat in:





Step 3:

Have a helper sit in the car and get them to start the car. Using STAR, actuate the Pitching motion of the struts. Be careful here as you must not allow the pump to ingest AIR, and you must ensure that the system has fluid in it all times. Fluid will empty from the reservoir, even when the struts aren't moving a lot.

If you do not have STAR, you can raise and lower the car repeatedly. This will not get 100% of the fluid out of the struts/pipework, etc as the system doesn't go to the extremes that the STAR does.

Keep topping up the fluid in the reservoir until you get nice clear fluid coming from the return hose.

Stop the engine.



Step 4:

Insert a new filter into the ABC cap:





To do this, press in on the spring, which releases a hook on the top half. When its in front you it will become obvious.

Next, ensure your ABC level is correct, and time to carry out a filter.

Step 5:

With the new filter in place, carry out another Rodeo on STAR, then change the filter again. Without access to star, I would drive the car around for a couple of thousand miles, then change it again.

Also, in hindsight, after looking at the new filter, I would drive with the new filter in place for a couple of thousand miles, then change it again, as it cant have taken that much crud out of the system in 15 minutes.

Check the level again and relax!

Full version here

 

[Philedge]

Good write up Alex. The one thing that would be of use is to mark the bucket the old fluid is going into with the volume to be flushed so that you know when you've just about finished. If you're flushing with 6 litres mark the the bucket at 5.5 litres and when the level hits this mark stop. Maybe not so important with 1 litre cans but with 5 litre bottles its a bit harder to judge and leave yourself enough fluid to do a final top up to the correct level.

Flushing a dirty ABC system is like squeezing zits as a teenager- the experts tell you not to do it but it feels so good to get all that s**t out.

 

[alexanderfoti]

Thank you.

Ah yes good point. I actually bought 12 litres as WIS says to use 15(!).

I poured the smaller cans into a new 5 litre pouring can and then poured in from that.

I kept flushing until the fluid coming out was green instead of black. Indeed! I cant imagine keeping that nasty old fluid in. Mine already had the newer 3 micron filter in it, so its been done at some point.

 

[alexanderfoti]

Another way to do it would be to empty the res, and fill it back up with new fluid. Just do that once a week for a month and the fluid in the system would be new after a month or so.

You would still have old fluid in the pipes up the struts without actuating with star though I think.

 

[Philedge]

Refilling the reservoir each week would just keep diluting crap fluid. Best do the flush as you've descibed as it gets lots of neat crap fluid out before it starts to get chased out with dilute crap followed by pretty clean stuff.

I think that there will always be dilute old fluid in the stuts unless you remove each strut and drain them individually.

The ABC experts suggest doing a second flush 1-2k miles after the first flush to hopefully get most of the last of the dregs out of the system after a bit of use.

 

[Lexman8]

Thanks for the write-up.

Did it need all 12 litres before there was clear fluid in the return line?

I bought 6 litres while it was on offer and I intend flushing the system next month. Sounds like I might need to buy some more fluid though.

 

[television]

10 litres is called for if you are going to do a full flush as laid down by mercedes, I fail to understand why the full flush is not done. All you need is 4 axle stand, or 3 plus the jack. There are no return lines on all 4 struts, and air that has got in stays there, the same as it does on a braking system till bled out.

 

[alexanderfoti]

Thanks for the write-up.

Did it need all 12 litres before there was clear fluid in the return line?

I bought 6 litres while it was on offer and I intend flushing the system next month. Sounds like I might need to buy some more fluid though.

I used around 6 liters before the fluid was coming out clean. So you should be OK.

 

[alexanderfoti]

10 litres is called for if you are going to do a full flush as laid down by mercedes, I fail to understand why the full flush is not done. All you need is 4 axle stand, or 3 plus the jack. There are no return lines on all 4 struts, and air that has got in stays there, the same as it does on a braking system till bled out.

I followed the procedure on WIS Malc, It states to remove the filter, put the return line into a bucket, and actuate the struts in a pitching motion whilst topping up the res.

Wasn't aware there was another procedure?

 

[alexanderfoti]

I see the other document (AR32.50-p-0021n) is for bleeding the system when replacing the ABC pump or struts.

13: Check ABC Front axle valve unit and ABC Rear axle valve unit for whistling/hissing noises. In case of whistling/hissing noises, Switch off engine at once! Raise the vehicle until the the suspension struts are relieved of load. Open bleed screws until hydraulic fluid slowly emerges, close bleed screws and raise/lower car 15 times.

 

[television]

I followed the procedure on WIS Malc, It states to remove the filter, put the return line into a bucket, and actuate the struts in a pitching motion whilst topping up the res.

Wasn't aware there was another procedure?

Only as you say Alex when a component has been disconnected or replaced .

It is like air in a braking system, pump the pedal up and you have brakes, release the pressure and the pedal sinks to the floor. while the system is under pressure from the weight of the car standing on the wheels, any air will remain where it is, sure the air will compress and you will have a mixture of ABC/Airmatic. Any air can only escape once all pressure is removed from that line.

Your write up should go in the DIY section Alex, its very good and well done and certainly better to have the front circuit with the expensive pump running on nice clean new fluid.

 

[alexanderfoti]

Ah yes I see what you mean. I will defo keep it in mind if I ever take any components on.

Had a bit of a shock on the last Rodeo, after the fluid flush. As the system pressure when running the Rodeo dropped to 60 BAR and didn't recover. The system kept going on the rodeo, but the car slowed right down.

Ah crap! I though, I went into actuations, and actuated the suction valve for 3-4 seconds, then went back to the rodeo and all was fine. Not sure what that was about!

 

[Swildey1985]

Hi all, i followed these instructions today, removed around 3 liters and was coming through green. Half way through the car stopped raising and i got the red abc light, had my helper turn off the car straight away, at no point did the resivioir run dry. Put everything back together again with a new filter. Turned the car on and the car rises and drops without any malfunctions or abc warnings. Drove the car about 3 miles rising and lowering with no problems. Checked the level is just below the notch when engine is aus - off! However now when i shut the car off i hear a hissing sound for about 20 seconds then stops, didnt have this before the flush, any ideas? Thanks all

 

[alexanderfoti]

Hi all, i followed these instructions today, removed around 3 liters and was coming through green. Half way through the car stopped raising and i got the red abc light, had my helper turn off the car straight away, at no point did the resivioir run dry. Put everything back together again with a new filter. Turned the car on and the car rises and drops without any malfunctions or abc warnings. Drove the car about 3 miles rising and lowering with no problems. Checked the level is just below the notch when engine is aus - off! However now when i shut the car off i hear a hissing sound for about 20 seconds then stops, didnt have this before the flush, any ideas? Thanks all

You have air in the system, you will need to release some abc fluid from each of the bleed points at each corner.

You may have a sticking suction valve if it happens again.

 

[Swildey1985]

You have air in the system, you will need to release some abc fluid from each of the bleed points at each corner.

You may have a sticking suction valve if it happens again.

Hi mate, just tried to look you up, im not too far away in eastbourne and have been looking for a mercedes specialist near to me! Thank you for your advise, i will look into bleeding them, is this something i can do at home? Thank you for your help

 

[alexanderfoti]

Hi mate, just tried to look you up, im not too far away in eastbourne and have been looking for a mercedes specialist near to me! Thank you for your advise, i will look into bleeding them, is this something i can do at home? Thank you for your help

Ah yes not too far!

Absolutely, you will need the car on axle stands to get the wheels hanging. Otherwise it's literally a case of undoing the bleed connections and letting fluid out (engine off!)

Make sure you apply penetrating fluid and counter hold the hex shaped housing of the line side of the bleed valve

Give us a call any time!

 

[Swildey1985]

Ah yes not too far!

Absolutely, you will need the car on axle stands to get the wheels hanging. Otherwise it's literally a case of undoing the bleed connections and letting fluid out (engine off!)

Make sure you apply penetrating fluid and counter hold the hex shaped housing of the line side of the bleed valve

Give us a call any time!

So good having knowledgeable guys i can go to if needed, so thank you. Will driving the car until i can do the bleed cause damage? Thanks again (i tried to re build my front valve block last summer but failed to undo 2 of the hydraulic lines, so if i keep getting sagging after about 10 days to 2 weeks then i may be paying you a visit Steve

 

[alexanderfoti]

So good having knowledgeable guys i can go to if needed, so thank you. Will driving the car until i can do the bleed cause damage? Thanks again (i tried to re build my front valve block last summer but failed to undo 2 of the hydraulic lines, so if i keep getting sagging after about 10 days to 2 weeks then i may be paying you a visit Steve

Ideally it shouldn't be driven as air in the lines will cause cavitation damage to the pump (potentially)

 

[brandwooddixon]

Absolutely, you will need the car on axle stands to get the wheels hanging. Otherwise it's literally a case of undoing the bleed connections and letting fluid out (engine off!)

Just to highlight your warning.
Hydraulic oil at 3000psi can cause some nasty injuries - hence no pump running when performing any ABC maintenance.