In this first part we will review the electric power steering (EPS) pumps of the A-Class model of the first generation Mercedes Benz: the W-168, introduced in 1997.
By Carlos Panzieri*
The main causes of failure are water infiltration between the cover of the electronic board and its base, wear of the brushes and the relative rotor.
There are two versions of this pump: a gear pump that requires the Emmetec 38X629 kit, and a rotary one that requires the Emmetec 38X630 kit.
Access to the electronic board
Acting on the tabs (image 1, green arrow), lift the cover that protects the electronic file.
Use Emmetec Z-07004 degreaser to thoroughly clean the edge of the lid, removing every trace of original putty.
Unscrew screws 2 and 4 in image 2.
Desoldering the blue wire that allows the ignition of the same pump (image 2).
Remove the board with the capacitors (image 2, green arrow).
Replace the original capacitors with the W-05219 and W05115.
Unscrew screws 1 and 3 in image 2.
Unscrew the four screws that secure the bridge to the base (image 3, green arrows).
Remove the electronic board (image 3, red arrow), an operation that will most likely lead to its rupture (which is not very serious since it has to be replaced anyway); The important thing is not to damage the base and bridge. For this operation, it is advisable to use fine tools and a PVC hammer.
Disassembly of the pump-motor unit
Unscrew the two screws that secure the tank to the base (image 4).
Remove the tank by uncovering the pump (image 0).
Remove the two torx screws (im. 06) and remove the pump body (image 7).
Remove the o-ring (image 7, green arrow) and replace it with the one that comes in the kit.
Remove the connection (image 8 – connecting the motor shaft to the pump), its rubber housing and the ring (image 9).
To avoid errors in reassembly, it is advisable to mark the position of the stator in relation to the base (image 185 green sign inside the red ellipse).
Please note: if this position is not respected, the motor may rotate in the opposite direction, resulting in damage to both the hydraulic and electronic parts of the pump.
Unscrew the two torx screws that connect the bottom to the stator (image 10).
Replace the o-ring with the one in the kit (image 11).
Remove the rotor (image 12) and check its condition; in particular, in correspondence of the point of contact with the brushes (image 13, green arrow), where the maximum allowable wear of the diameter is 1mm. As long as tolerance is respected, it may be sufficient to lightly brush the point of contact; if not, it is essential to replace the rotor itself with the code T-00078, T-00078A or T-00078B.
Using a torx wrench, remove the two nuts and the brush plate (image 14).
Replace the o-ring with the one in the kit.
Check the bearing (image 14), and if necessary replace it.
Attach the new V-04023 brush plate and screw in the two screws.
Reassembly of the pump-motor unit
Insert the rotor with the help of a PVC hammer.
Check the position of the wiper blades, and if they are not in contact with the rotor, pull them out with a screwdriver.
Assemble all the previously disassembled components (replacing all those that require it) in the reverse order of disassembly.
Test the pump-motor unit without the electronic regulation system, with a 12V and 10 or 15A maximum power supply, checking the operation of the motor and that the no-load consumption is less than 10A.
In the next chapter we will delve into the details about the rotor and gears, replacing the electronic board and how to close it.
In the meantime, for more information and clarification, visit the websites of www.emmetec.com and www.orpav.com, or www.jadausa.com, your distributor for North, Central and South America, to request technical courses.
* Technical Consultant at Emmetec & Orpav