ABC chassis questions and answers on the most important topics:
- Do you have to top up oil on the ABC chassis?
- Can you lower an ABC chassis?
- Which oil for the ABC chassis?
- Why is my vehicle sagging?
- Why is my ABC landing gear crooked?
- How can I see that my ABC landing gear is leaking?
- What is the difference between an ABC and an AIRMATIC suspension?
- How many generations of the ABC are there?
- Why is my ABC landing gear spongy?
- How do I know that my ABC pump is defective?
- Why is my vehicle hopping?
- Why does the ABC landing gear squeak?
- ABC hydraulic pump no longer builds up pressure?
- Why does the ABC hydraulic pump make noises?
- Can my hydraulic oil get too old?
- Can an ABC suspension be converted to a coilover suspension?
- Do you have to flush an ABC chassis?
- Why doesn't my ABC landing gear start up?
- How do you bleed an ABC chassis?
- What does an ABC magnetic filter do?
- What is pentosin?
- How do I check the oil level in the ABC chassis?
- How long is the lifespan of an ABC chassis?
- Can you calibrate an ABC chassis?
- What is an ABC pressure sensor?
- How do I change the ABC filter?
Do you have to top up oil on the ABC chassis?
The ABC trolley is a hydraulic trolley. It is a self-contained hydraulic system with a special oil supply. According to the specifications of Mercedes-Benz, a maintenance-free system. That's not true. The oil ages, leaks and defects occur.
Can you lower an ABC chassis?
It has to be said straightforward, it is death for any ABC chassis. Technically, it is a bit more extensive and to understand it, a drawing is required if the background knowledge is missing. We still try this way. Every Mac Pherson shock absorber has a coil spring, just like the ABC shock absorber on every model. The coil spring is progressive. What does progressive mean? The more the spring is compressed, the harder the spring becomes. Each spiral spring is installed with a certain preload so that the softer area is not too large at the beginning and that the strut cannot bottom out. What happens when a shock absorber hits the bottom, the piston rod of the damper hits the bottom valve in the shock absorber, destroys the bottom valve and the bottom valve is responsible for proper damping. If the bottom valve is destroyed, the damper is defective and cannot be repaired (total loss).
You can easily move the piston rod back and forth like an air pump. Lowering has become a regular reason for complaint, because the vehicles are so easily lowered with the coupling rods. What happens when lowering, the coupling rods simulate a vehicle level below 0 for the level sensor. The hydraulic head (plunger) is moved in further, thereby relieving the preload of the coil spring, and the car sags. The spring loses its hardness, which it needs for cushioning, bumps and potholes. The spring is now so soft that the shock absorber can break through even with the smallest bumps. It should be mentioned here that small spring travel limiters are installed ex works, but they are defective within a very short time. Bottom valve, plunger and spring travel limiter are always defective in lowered vehicles, complaints are made with great pleasure, but this is not a reason for complaint. Lowering an ABC chassis is like flexing one or two turns off the coil spring on a normal Mac Pherson strut. What the hobbyists like to do to lower their vehicles. You just forget that the piston rod continues to sink into the damper. We are friends of lowering and sporty looks ourselves. So we took a closer look at the lowering of an ABC chassis in our company and carried out tests. Every vehicle with ABC chassis has a dimension of 72 cm on the front axle and a dimension of 70 cm - 72 cm on the rear axle, depending on the model. The whole thing is measured from the ground through the center of the wheel to the edge of the wheel arch.
There is good news that we found from our testing. Lowering is possible, but only to a certain extent, depending on the vehicle model. Then electronics have to be used like Carlsson does. Their lowering modules can do what all other modules cannot. When driving slowly 10 - 15 km, to pose in front of the ice cream parlor, the car is very deep and the faster you drive, the higher the vehicle goes in order to guarantee all functions of the ABC chassis and to avoid damage. Many who lower their vehicle also do not know that the vehicle is electronically lowered again from 60 - 120 km to 2,5 - 3 cm, which is added to the lowering. You will be amazed that the driving behavior on the highway is completely screwed up and the car hops, crashes and you soon fall out of the car. Then if something is broken, it's the other's fault. Carlson can, of course, pay decently with the module between 1300 - 1600 € depending on the model, that of course hardly anyone wants to invest. But it is the only solution for extreme depth. 50 - 80 € for coupling rods is of course cheaper. In the end, you prefer to pay the money for struts. Good for us. If we lower vehicles, then only with the Star Diagnosis and only to the extent that we have worked out for each vehicle. But now to the actual topic, we have built ABC struts that can be lowered and bring a lowering of 3 to 4 cm from home. The chassis works without problems and comfortably, you have a sporty appearance and everything without manipulation. Because even lowering modules, no matter what type, are only manipulations of the existing electronics and the electronics also show the module, no matter which, as a fault in the system. Many errors in the ABC system are caused by modules because they tend to break and malfunctions occur. We installed and tested all prototypes of suspension struts in our own collector's vehicles. The source of the graphic representation is Wikipedia.
Which oil for the ABC chassis?
A 001 989 24 03 - 10 (central hydraulic oil) for your tandem pump, this is responsible for power steering / power steering and the ABC chassis (completely hydraulic chassis). The oil offered here can be used for both systems, power steering and ABC chassis. When replacing the tandem pump, you need approx. 5-6 liters to refill. If the oil is contaminated and old, it must absolutely be replaced, because old oil immediately destroys your new pump. Old bad oil can be recognized by its coloration brown, dark brown or even black. You can recognize new or good oil by its light green color. You can also find the right oil here.
Why is my vehicle sagging?
The sinking when standing with the engine off is due to the valve blocks of the VA and HA. There are metal valves in there. Over time, dirt and soot residue build up on it and the valves do not hold tight. If you rinse the system properly, use new oil and a new filter, it usually works again. If the oil is burnt, I advise you to switch with flushing anyway, because sooner or later the tandem pump will die. Incidentally, it is often the case that more than one strut sags. After all, the dirt collects everywhere. Everything speaks for us like dirt in the facility.
Why is my ABC landing gear crooked?
This can have several causes. In our experience, one of the following reasons can cause the vehicle to stand crooked:
- Bent coupling rods
- Level sensors defective
- defective shut-off valves in the valve block
- leaky struts
How can I see that my ABC landing gear is leaking?
In order to rule out leaks in the ABC systems, a visual inspection of all hydraulic parts is necessary. The following parts should be checked:
- Hydraulic lines
- Struts
- Hydraulic pump
- Valve units
- ABC cooler
Suspension strut SL 
strut 
Strut down 
Hydraulic connection quick release 
Valve block 
Valve block in front 
Valve block with hydraulic hoses 
Valve block with hydraulic hoses at the front 
Valve block with hydraulic hoses 
Rear shock absorber
What is the difference between an ABC and an AIRMATIC suspension?
The main difference is that this ABC chassis is an electro-hydraulic chassis. It works fully hydraulically with an oil pressure of 200 bar and is installed in Mercedes and AMG vehicles with high engine power due to its high reaction speed.
The Airmaticsystem is a fully-fledged air suspension with air bellows and a compressor like a truck. The reaction speed is lower here and is used in vehicles with less power and less sporty driving style. The further development of the AIRMATIC chassis has been very well advanced in recent years.
How many generations of the ABC are there?
There are three generations of the ABC chassis.
Why is my ABC landing gear spongy?
The reasons for a spongy ABC chassis can be quite diverse, in our experience the following checklists are the main reasons.
- ABC shock absorber defective
- ABC hydraulic pump defective
- Vehicle is in the ABC emergency mode (red error message "ABC defective, go to the workshop")
- Vehicle too deep
- Incorrect wheel alignment or no wheel alignment at all (after an accident or repair)
How do I know that my ABC pump is defective?
If the pump pressure drops to 160–170 bar, the pressure sensor reports too little pressure in the system. The white error message in the instrument cluster reads: "ABC defective, go to the workshop". If the pressure then falls below 100 bar, the chassis goes into emergency mode and the shut-off valves in the valve units are closed.
This is done to prevent the hydraulic oil from flowing back out of the struts. From 99 bar you will then receive the red error message “ABC defective, go to the workshop”.
You will also notice that your pump is defective if it is leaking, this happens quite often and should be ruled out first.
Why is my vehicle bouncing or bouncing?
The most common reasons why a vehicle with ABC chassis hops or bumps are as follows:
- ABC chassis in emergency mode
- ABC pressure accumulator defective
- Vehicle was placed too low
Why does the ABC landing gear squeak?
The landing gear squeaks because the ball joints are defective. A ball joint is a wearing part. Inside there is a joint lubricated with grease, this grease gets old and resinified, so the joint is dry and squeaks.
ABC hydraulic pump no longer builds up pressure?
If the ABC pump no longer builds up pressure, there can be many reasons, let's start with the worst. The pump is damaged internally; only a complete replacement will help.
The suction throttle valve is defective. The suction throttle valve regulates the amount of oil sucked in by the oil pump so that an oil pressure of 180 bar to 200 bar can be built up and maintained in the ABC system. When de-energized, the valve is closed in order to maintain the pressure in the system.
It also often happens that a cable break is the reason for too little or no pressure in the hydraulic pump. This cable regularly breaks right behind the plug of the suction throttle valve.
Finally, the slightest evil, the landing gear is simply not vented, which means that air in the landing gear interferes with the pump function.
Why does the ABC hydraulic pump make noises?
This often happens due to a pump defect, more precisely a bearing damage in the pump.
This happens because dirty oil clogs the microsieves and the pump fails to self-lubricate. The main bearings run dry and are defective and therefore make loud noises.
Sometimes there is also a defect in the pulsation damper. This manifests itself in crackling noises in the pressure lines or flow noises, humming noises in the passenger compartment.
Can my hydraulic oil in the ABC chassis get too old?
Yes! Pentosin oil is an oil that is similar to brake fluid. This hydraulic oil has a shelf life of 4–5 years and is sealed in a container. When using the vehicle and changing from warm to cold as well as removing the particles from the inner walls of the hydraulic hoses, it is always our recommendation to change every 30.000 kilometers. The hydraulic oil change is not always tied to kilometers, but the color is also crucial when checking. Originally it is light green or mint green, should the discoloration develop towards brown or even black, it is time to replace the oil.
Another reason why the hydraulic oil (Pentosin) should be replaced is that it is hygroscopic, i.e. it absorbs humidity, so that it has to be immersed after a maximum of 5 years anyway to avoid rust and water in the system.
Oil coarse filter method 
Oil comparison 2 
Oil comparison
Can an ABC suspension be converted to a coilover suspension?
Yes you can! But that is not allowed in Germany, only in the USA.
Do you have to flush an ABC chassis?
A resounding YES !!!! Through wear and tear and dissolving hydraulic hoses as well as metal abrasion, through use, a lot of impurities arise in the system that have to be flushed out.
Why doesn't my ABC landing gear start up?
There can be broadly two reasons for this. First of all, you should perform a visual inspection of the ABC pump to rule out any leaks. If you have done this and the pump has come dry, in most cases the only question is that an electronic component is defective and prevents it from starting up.
How do you bleed an ABC chassis?
It's relatively easy. An ABC chassis is vented by moving it up and down 20-30 times. The air is expelled by the oil pressure through the return and escapes through a small hole on the dipstick.
The system should be closed, i.e. the storage tank. Through the opening of the dipstick you can then observe whether foam is still forming in the system. If there is no more foam in the storage container, the ABC system is vented.
What does an ABC magnetic filter do?
It uses a sieve and magnetic force to filter out metal debris and metal shavings that occur when the pump is damaged or worn. Furthermore, it is the shop window of the ABC chassis. The fact that it is transparent makes it easy to see the color of the oil (mint green = good and black = bad) and any impurities that may have been trapped.
ABC Madnet filter 
ABC magnetic filter structure
What is pentosin?
Pentosin is a hydraulic oil similar to brake fluid. The color should be mint green. The oil is used for power transmission in hydraulic ABC systems.
How do I check the oil level in the ABC chassis?
Let the vehicle run and move it all the way up and down again. Then wait 2 minutes until the end position is reached. You can now turn off the vehicle and have a coffee for 5 minutes.
After the waiting time, please pull out the dipstick and the oil should be on the "Engine off unloaded" mark. This is the upper mark!
The most important thing is that the system is properly vented. This is a common mistake. If the air is completely out of the system, the error results in the oil level being too low. Then the oil is no longer sufficient when starting up and the pump draws air, which results in a white or even red error message "ABC defective, go to the workshop".
Now comes the important thing! When oil is then topped up, the pump starts not to work alone again.
Pressure must be applied to the system again, this is usually done via the storage tank, about 1–2 bar. Then the pump draws oil properly again and it can be vented. This is a common mechanic mistake and often goes undetected.
The big problem here is only if the ABC pump runs too long without oil, it has no self-lubrication and there is a risk of bearing damage in the pump. Your main bearings run dry and the first chips are formed in the system, which can lead to major damage in the system or even total loss.
In this video you can see how to properly commission an ABC pump.
How long is the lifespan of an ABC chassis?
With regular maintenance even at a young age, an ABC chassis will last a lifetime.
Experience from the last 20 years shows that 500.000 kilometers and more can be done without problems.
Can you calibrate an ABC chassis?
Yes, you can do that in the specialist workshop! For this you need the star diagnosis or a wheel alignment stand.
What is an ABC pressure sensor?
The pressure sensor reports the respective hydraulic pressure to the control unit. This is regulated to approx. 180–210 bar via the suction throttle valve.
There is a pressure sensor that monitors the system pressure and in the newer chassis there is a pressure sensor that monitors the suspension struts.
How do I change the ABC filter?
The ABC fine filter is located in the hydraulic oil reservoir. Turn off the engine and unscrew the cover, the oil filter is attached to the storage tank there by a simple mechanism.