Electric steering assist DANGEROUS
 

I was privileged to see and test a 2012 ML350 after a electric steering belt failure.


Without the electric assist it is virtually impossible to steer the vehicle. So when you loose the electric assist there is virtually no steering.


The mechanics of the electric steering is such that you not only loose the assist you now have to overcome the drag placed on the steering by the steering assist components.


Let me explain. The electric motor spins a recirculation ball nut that sits on the steering rack. The grooves on the steering rack is at, I guess, 8 degree angle, or even less. It is such that the relative small motor can deliver enough power. For you to turn the steering without the assist you have to apply enough force to make the balls in the nut move in the groove. It is like applying enough force on top of a nut to make it spin on the bolt. Not quite but you get the idea. It takes a lot of force. With the vehicle standing still I was able to turn the wheels 5 degrees.


Not only do I think this is unsafe or just out right dangerous it is extremely expensive to repair. Mercedes do not supply any of the internal parts for the steering rack. You have to buy a new rack complete with motor and all. $2600 some dealers want $2900 for one. To remove and install it they have to remove the engine and dismantle the passenger side suspension. The total cost for this repair is in the order of $10K to $12K. That is if you live to tell the tale.


The most frightening is the you can loose assist without being in a accident, just driving down the street as electrical cable problems caused a multitude of complaints to the TSB.


I own a 2010 ML350 CDI and I am not upgrading to a vehicle with the belt drive Electrical assist steering ever. As for Mercedes I always thought they have safety in mind when they design their cars. I guess not.

Many if not most of the newer vehicles are total electric steering. It is just plain cheaper and cut weight in half compared to the old way.

You are quite right most new cars have them. It is not the weight since most electric steering racks are actually heavier than the Hydraulic assist steering racks.


It is the fact that you have to turn the power steering pump on hydraulic systems even though you go strait for miles. The electric steering only draws power when you steer. So that is where the energy savings come in and why it is popular.


The problem with the belt drive versus the gear drive Electric steering is that the belt drive makes it impossible to steer when it goes out. The belt is also a weak part of the design. It can strip the teeth off. Like what happened with the one I saw. The Mercedes steering also have the issue with the cable that cause the driver to loose steering assist.


I have a vehicle with electric steering, my wife's car over 70K miles on it. Never had any problems with it, but it's not a belt drive. With the engine off it is still relatively easy to steer unlike the Mercedes steering.

My understanding is that electric cuts about 30% of the weight compared to hydralic, but it does not matter as this is the way all the MFGs are moving.

From Car and Driver article:
"Makers are moving aggressively to EPS because eliminating an engine-driven hydraulic pump increases gas mileage by about 1 mpg. "
"EPS is not all sweetness and light, though. Engineers are well aware of its ­inherent shortcomings, some of which prompt our negative bias toward this type of power assist. These include far more friction and inertia than HPS."
"Most of EPS’s friction comes from the ball-screw mechanism that converts the motor’s rotation into the linear force used to move the steering rack left and right. There have been many attempts to cut EPS’s inertia."


The side saddle unit used in the newer ML's are belt drive.
The big problem is that when the Electric assist fails you cannot steer your vehicle. The inertia from the recirculating ball and nut is too high. I have seen this first hand with the stripped belt ML.

Electric steering is around since 1986 but with the motor attached to the steering pinion rather than the side sadle motor type (Belt drive) being used in the ML.

Have you heard or read about any cases where accidents happened with ML's caused by power steering loss?

The one I have access to did not however it ended up in the field. When I researched the electric steering used in the ML I found several owner complaints. My biggest issue with the electric assist steering is the design. As you can see in Car & Driver everyone recognize the drag is high but Mercedes installed the steering to save 1 MPG. The disregarded the safety issues with the unit. Then there is the issue of no internal service parts. It just tells me that this steering has a lot of issues that will surface when the 2012 models get to higher mileage. That is when you will see more accidents I believe.

No component is perfect. You can look at any car part and say it's "dangerous". Railing against ES is akin to pounding sand. Let's talk about how dangerous tires are when they blow out....fruitless and pointless.

I kinda get the idea that someone pee'd in you wheaties today:p:

Yech, Wheaties...:v:

When you don't know anything you can think you know it all. To refer to bodily excretions as an argument confirms it.



I bought my first Mercedes in 1983 and has never been without at least one. I think it is a great car but I can recognize when a component is unsafe.



Tires today are probably as safe as you can get. I had a blowout on my first ML the tire was destroyed and I hardly noticed it in the car. On top of that there is no safer alternative for tires. Unlike the side saddle electric steering.

What the OP chooses to "upgrade to" is entirely his choice - and for whatever reasons he chooses for himself.

I have not seen any problems with any Mercedes made in the past 3 yrs with electro-mechanical steering...

A little late in answering, but...

The W163 did have some (alleged) crahes due to loss of hydraulic steering, due to hose blowouts from a clamp failure. I can say that when my serpentine belt snapped, causing loss of steering AND cooling, I couldn't turn the wheel with the car standing still - the tires are just too big. Even moving at 40mph, I had to hang on the wheel with as much body weight as I could to get it to turn.