dannyfiveforty

I have recently changed my ABC pump on my 2003 SL500 as it was faulty.

The new one works perfectly except for a hissing noise I get. It is best heard when the engine has been switched off, it can last anything from a few seconds up to over a minute depending on how much the suspension has been worked.

I have attempted to bleed the front lines twice but have had no air escape.


What does it sound like to you?

Many thanks
Dan

mkirincic

Are you sure its from the ABC pump? While it's making that hissing noise try pushing up down on the front fender to compress the suspension. Does that change the noise in any way? I had my ABC pump replaced recently and I did not have that hissing noise issue? Unless its coming from the power steering side of the system.

next2pool

Pull the cap off the reservoir and see if fluid is coming out of the return line/filter while it is hissing. That may give us a clue.

dannyfiveforty

Thanks, I pushed up and down on the fenders and it made no difference to the noise. I will study the return flow tomorrow when it is light out. I had a little squeeze of the return pipes to the pump and return pipe to the reservoir and this made no difference to noise either.

The noise is definitely coming from the actual pump.

Thanks

simade

I have a cl500 2003 that does exactly the same thing (hissing from pump).
Have you been able to find out what it is, is this normal, is it a fault, and what is the remedy/repair required if necessary.
Would gladly appreciate your feedback.
Thanks

TTtodd

Is is hissing when the engine is running?

Did you install a new pump or rebuilt?

Complete a rodeo after install?

Positive it is the pump?

May want to start with a spay bottle of water/soap mix. Spray in there where you hear the hissing. Maybe you can find the location.

dannyfiveforty

A friend of mine installed a genuine LUK pump onto mine, as the original was getting weak and noticed it started to hiss towards the end.




The new pump will only hiss after the engine has been shut off if I have raised the car using the button. A couple of days after the install I booked it into MB UK and they checked the install, checked for air locks etc, they charged me nothing to do this and confirmed the job looked like it had been done by a professional. I mentioned the hissing and there words were there is nothing to worry about the pump is operating as it should. It has been a couple of months now and there is no suspension issues at all.


Whilst the engine is running on yours before you press the button open the door that is on the same side as the pump and valve block (mine is RHD so its passenger door) listen near to the glove box/door shut area for a hissing noise, then press the button and see if the noise stops? Then try starting the car for a journey and not pressing the button at all, when you stop and get out is the hiss there? Or only when the button has been pressed?

dannyfiveforty

Also, Yes my hiss is definatley the pump as I had my stethoscope on it, I tried the spray bottle with a soap solution and it showed nothing. I also bled the shocks after install as the system had been opened, this made no difference.


I am happy however that MB UK insist the install is good, and the hiss is nothing to worry about, plus also its only there if the car has to be raised..


I will be interested to see how yours compares to mine however

simade

I will be doing a 60 mile journey today, so I will make a detailed examination of the strange hissing sound. As in the video that starts this thread, the hissing from my car is EXACTLY the same and definitely comes from the pump.
Once the ABC system is warmed up, I will check hissing a/before switching off the engine b/at normal ride height c/at both raised heights and d/also when the engine is switched off.
There are no oil leaks from my ABC system (and I hope it stays that way).
I did have issues with it a couple of months ago, where the rear raised up on its own and refused to go down. After careful inspection, I discovered bubbles in the oil when bleeding the unit. I subsequently serviced my rear valve block (o-ring change), flushed the entire system and fitted a new filters. Now the car maintains its height at all levels when the engine is on or off.
My rear suspension is harsh and bumpy. Changed the rearmost accumulator tucked above the exhaust and this improved the ride by about 50%. Rear ride is still harsh, bumpy and skitty, but derivable. I plan to change the rear accumulator attached to the rear valve block hoping this will also make a difference.

simade

After my 60 mile journey, I checked the hissing from the pump. It appears to be only there when the engine is switched off and at any height setting.
As mentioned the ride on the rear suspensions are harsh, bumpy and skittish, but the car is still derivable. I plan to change the accumulator attached to the rear valve block next week and hope that cures all (or at least some of) the problems. Desperate for the smooth, silky and surefooted ride.
As I did not own the car from new, all I can say about the ABC system is that it is difficult to Pin-Point actual cause of a problem/issue. Agreed that parts are expensive, but once changed they last for years. The actions I wish to avoid, are changing parts I do not have to (how I wish I owned a bank). One thing for sure is keep your hydraulic fluid clean with regular changes including the micron-filter. I intend to do this every six months.
MOT is due this week and I hope she sails through.
If anybody has had experience with and solutions for the hard ride, please give me some direction.

simade

Rough Ride, Hard Shocks, Bouncy Suspension - Problem Solved
Before I get to that, took the car in for its annual MOT (Wednesday) and she passed without any advisories - so I'm good for another year. . . phew!!!
Ordered a Return Line Accumulator from Mercedes and received it today (accumulator fitted directly to the rear valve block with two pipes). Thankfully, the accumulator can be removed and fitted without touching/removing the valve block. The only thing that must be done to make the removal easy, is to completely disconnect the short C shaped hydraulic pipe that connects the valve block to the accumulator. This will allow you to maneuver the accumulator away once the second (flexible) pipe is removed. Oil loss is minimal, but still remember to top up the hydraulic oil in the reservoir once the job is done.
It took about an hour to prepare the job, do it and clean up. Started the car, raised and lowered her about ten times and went on a test drive.
What a difference! The car is now smooth, stable and sure footed. No more harshness, no bouncing, simply smooth and silky. I was elated.
I had also made an appointment with 'Star Motor Services in Reading' to connect my car up to SDS for ABC calibration. Met the boss Ian and one of his key men Simon, both helping to do the calibrations.
They performed 1/ a Plunger Sensor Calibration 2/ a Load Test Calibration and finally 3/ a Suspension Height Calibration. . . their service was excellent, courteous, friendly and affordable.
Ian gave me technical advice on another MB (W140) that I own and I am personally encouraged to return to his workshop (www.starmotorservices.com).
In conclusion to my previous Hard Ride Rough Ride problems this is what I have learnt.
a/ ACCUMULATORS play an extremely important part in the dampening of shocks and movement of the suspension system.
b/ The large Accumulators found at the front and the rear are in series with The Supply Side of the Hydraulic System. Front serving front and Rear serving rear (thats why they have only one pipe feeding them).
c/ The smaller Accumulator found next to the rear valve block is in parallel with The Return Side of the Hydraulic System, serving both the Front and the Rear and that's why it has two hydraulic pipes feeding it.
d/ Every suspension has a two way action to its bounce, Compression and Expansion. The large Accumulators assist the Compression and the Smaller (Return) Accumulator assists the Expansion. There is a much greater impact force on Compression that's why the supply Accumulators are larger and also why you have one for the fronts and another for the rear. Forces on expansion are far less and that is why you have a smaller and single Return Accumulator for front and rear.
e/ If your ride is rough, hard, bumpy (and struts are not leaking), and you have changed the Large Accumulator (Front/Rear depending on which side is poor) and the ride quality is not fixed, THEN you also need to change the Smaller (Return) Accumulator to achieve the comfortable/surefooted ride the car (W215) should have.
f/ The last Accumulator located by the rear side of the Front (right) Wheel Arch, known as the Pulsation Damper, removes pressure spikes from the supply side of the Hydraulic System and assists/dampens the load on the Hydraulic Pump.
So far, I have changed both Accumulators located at the rear of my car. The accumulators to the front of my car are still working, but I will change them very soon to keep the ride at its best.
Lastly, damaged accumulators release debris into the hydraulic system oil so I will be flushing my system and changing both ABC and Power Steering filters.
Keep your system clean and your ABC will live long... Vrroooommmm!!!

Fighter

Hello, did you solved the hissing sound from the ABC pump? I know the post is old but I'm interested in why the pump sounds like that when you shut off the engine. My pumps sounds really similar and also makes hissing when is in idle. Any ideas? Best regards.

Ludo2676

Hi Danny, did you ever workout what the hissing was as my CL500 is doing the same and I can not workout what it is.

Steve

Ludo2676

Hi Danny, did you ever workout what the hissing was as my CL500 is doing the same and I can not workout what it is.

Steve