Broken Front Spring – C Class Mercedes – W203 and others
It was MOT time again and I confidently took the wife’s C200 to the local Testing Station. The tester and I were flippantly discussing the benefits of strut suspension over the corroding W210 E class spring and perch arrangement when he detected a problem with my own off side front spring. The spring had recently broken on the final bottom turn of the coil and needed replacement, so off I went fail certificate in hand, to get the job done!
EuroCar Parts were the best and most convenient source of a new spring, I opted for the OEM spec Sachs spring at a very reasonable £35.00 although I could have opted for a far cheaper economy spring should I have wished.
The task of removing the front strut on a C Class Mercedes is in itself far simpler than most strut suspension vehicles around, however the removal and replacement of the spring from the strut is in many cases beyond the scope of the home mechanic (Unless you make a special tool). Do not think that you can just buy a cheap set of spring compressors from the auto-store and complete this task, as you will most probably fail and at worst end up damaging yourself or other object of value in your working surroundings! If you are in any doubt of your competencies in carrying out this task I advise entrusting this one to an independent repair shop. But if you are ‘gung-ho’ read on.
For those who are interested in tackling this job, here we go….
Slacken the road wheel bolts and jack up and support the vehicle on the working side, the forward jacking point is the perfect position to lift for this job as it leaves the suspension in free air which is ideal. Remove the road wheel and lift the bonnet/hood.
Unclip the brake pad sensor wire and ABS cable from the black plastic holder on the suspension leg, note that both wires run beneath the hub carrier bolt to their sensors, this will be important on reassembly. Use side cutters and snip the single tie-wrap that secures this bracket to the bottom of the leg. Push in the upper and lower latch fingers of the bracket and rotate it around the suspension leg, once free move it out of the vicinity upwards of the flexible brake hose.
Using a 15mm spanner and 21mm socket almost remove the upper hub carrier to leg bolt. Prize off the black plastic cap on the suspension strut top in the engine bay then using a 21mm ring spanner and a 7mm Hex key wrench undo fully the top nut and remove the retaining bracket.
Place a support under the brake rotor/disc (a wooden block is perfect for this) and then lower the vehicle to take the weight on the support. Lower the vehicle enough to allow easy removal of the upper roll bar link ball joint from the suspension strut. This is a 17mm spanner job with a 7mm socket to hold the central threaded portion from rotating. Once removed, free the drop link from the strut and pull it to one side. Raise the vehicle again to working height.
Undo and remove the bottom strut to hub carrier bolts with a breaker bar and socket (2x 19mm), now completely remove the upper carrier bolt and pull the hub outward from the vehicle. The top lug on the carrier should now disengage and allow you to apply downward pressure on the hub and release the complete strut from under the car. Be careful not to damage the sensor cables when manoeuvring out the strut. It will easily come downward and out if you direct the lower end toward the passenger foot well whilst holding down the hub assembly and lower arm. You should now have the complete strut out from the vehicle. Have a drink of tea… you will need it.
If you open the large blue box that holds the new Sachs spring you will wonder if they have supplied the correct part, as it is just soooooo.. long!
The strut itself has aluminium casting that platforms the base of the spring and a pressed steel top cap and a rubber top bush that sockets into the suspension cup of the chassis. For future reference it is good to familiarise yourself with the orientation of this rubber top mount with the shape of the cup inside the wing top. The broad rubber locating flute is inboard and thinner one outboard – useful to note before reassembly.
If you have access to a set of expensive twin yoke spring compressors that is great, if not read on..
The next step is to make a ¼ inch steel plate that saddles the strut underneath the alloy support spring platform and extends a couple of inches out either side, drill two holes to accept the threaded portion of your standard spring compressors. Latch the upper hooks as high up the spring as possible on either side and use a couple of small hose clips (jubilee clips) on the spring coils, tightened to prevent the compressor hooks slipping down the coils as you compress. You will need to compress the spring almost fully, until it is nearly coil-bound to be able to remove the bush and top cap – ensure that you are comfortable with your construction and that it is as safe as it can be, the fitted spring is and will be under extreme tension as you proceed and it needs to be intrinsic for your safety and well being. Fully compress the spring.
Once compressed, use a small screwdriver or thin drift to tap round the locking collar on the threaded portion of the strut just as it exits through and seats just inside the Metalastic top bush. You may need to hold the strut from rotating with a 7mm hex key. The strut cartridge is biased to retract, which does not help either disassembly or reassembly, so you will need in some instances to lever the top bush slightly out of the upper spring seat to carry out these operations. Once the locking collar is removed you can lift off the top bush from its taper seat on the strut shaft. The spring can now be carefully uncompressed, ensuring that you balance the release of tension equally between the two spring compressor tools as you go.
Remove the broken road spring and fit the new one, locating it into rubber slot on the alloy lower support platform. Re-attach the compressor tools and fully compress the spring – use the same vigilance and safety precautions as before. Once fully compressed, locate the top cup onto the spring and refit the upper bush, screwing home the locking ring on the threaded shaft fully. Once you are sure that all is well and the spring is seated correctly and the damper rod is secured seated fully into the top bush, begin to release the spring compressors in the same way as before.
Once fully relaxed the compressors may be removed and the assembled strut refitted to the car. Remember to position the top bush so that the larger rubber locating flute is inboard and the thinner one outboard, this will assist greatly in relocating the strut back onto the vehicle.
Reassembly is a direct reversal of removal. Congratulate yourself on a job well done !