W123 and W126 front brake rotor replacement, with bearing and pad change included.

[whunter]

W123 and W126 front brake rotor replacement, with bearing and pad change included.

The steps:

1. Break loose the lug bolts.
2. Lift and support car with jack stands.
3. Remove wheel.
4. Remove the two 19 MM caliper bolts.
5. Remove the caliper.
6. Remove grease cap on the center of hub.
7. Use a 5mm Allen/hex wrench to loosen the pinch nut on spindle.
8. Remove spindle pinch nut.
9. Thump the rotor brake surface with the heel of your hand to pop loose (be ready to catch) the outer bearing.
10. Slide the rotor off of the spindle.
11. Remove the inner and outer bearing races with a punch and hammer.
12. Clean the grease from inside of the hub.
13. Remove the hub from the rotor with an 8mm Allen/hex. Note: You can use a 3/8 drive to 1/2 inch adapter with a breaker bar + a piece of steel tube for leverage = cheat by fastening the hub to the wheel with 3 bolts plus have someone stand on the inside edge of tire while you break each of the five Allen bolts loose.
14. Cleaned the five removed Allen bolts with a wire brush.
15. Clean off the mounting surface of the hub with sand paper/wire wheel/brake cleaner as required.
16. Position the new rotor on the hub.
17. Put Blue thread lock on the Allen bolts sparingly and install them into hub.
18. Torque the Allen bolts to 80 - 85 pounds.
19. Remove the hub/rotor from the bracing wheel.
20. Use the old bearing race to install/drive-in/seat the new inner and outer race with a hammer and punch, gently but firmly.
21. I suggest you Pack the bearings using a grease gun and bearing packer.
22. Pack the inside of the hub with grease, not too much.
23. Install the inner bearing and wipe grease on the inside/lip of the seal and install the inner seal with a hammer, gently but firmly.
24. Clean the old grease off of the spindle and apply new grease on base of spindle where the seal will ride.
25. Slid the rotor and hub onto the spindle until seated.
26. Install the outer bearing into the hub.
27. Installed the spindle nut.
28. Spin the rotor with light hand pressure, tighten the spindle nut down firmly using channel locks UNTIL the rotor stops moving, then back off nut tension 1/4 turn and tighten the 5 MM pinch bolt.
29. Check for bearing slop/play, smooth spin of the rotor, and binding.
30. Put some grease around the spindle nut and a little inside grease cap.
31. Install the grease cap on the hub.
32. Install the caliper being sure the pistons are fully seated/compressed into their bores.
33. Put some blue thread lock on the caliper bolts, Install and tighten.
34. Remove the old brake pads.
35. Install new brake pads and sensors.
36. Install the front tires, snug the wheel lugs best possible.
37. Lift the car, remove the jack stands and lower.
38. Torque the wheel lugs 85 – 90 ft lb.
39. Get in the car and pump up the brake pedal until firm.
40. Test drive, listening for noise/feeling for vibration or pulling.


Some good Pictures can be found here.
How To Replace Front Rotor W123

[Stretch]

Nice one - I'm not sure if everyone still uses them but the little radio interference springs can also be added to the grease in the cap at steps 30 / 31.

[JHZR2]

Nice but the dial gauge method should be incorporated, preferably with the right p/ns for the stuff from HF or equivalent...

Also would like the MB p/n and correct mass for bearing/cap shown.

[Rooster300SD]

I was under the impression that there were some differences between
the two models on doing the front rotors? They're exactly the same?

Jeff

[ashedd]

They are the same except the SD has vented rotors and the w123 is solid.

Originally Posted by Army

Nice one - I'm not sure if everyone still uses them but the little radio interference springs can also be added to the grease in the cap at steps 30 / 31.

What's a radio?

[JHZR2]

Originally Posted by Army

Nice one - I'm not sure if everyone still uses them but the little radio interference springs can also be added to the grease in the cap at steps 30 / 31.

Good point... Can they be purchased over fastlane or APE? Some will not know if they have them until the caps are off, so better to have them in advance to do things right. Likely why some w123 cars Ive been in have good reception, and some have zero, especially on AM.

[whunter]

Originally Posted by JHZR2

Good point... Can they be purchased over fastlane or APE? Some will not know if they have them until the caps are off, so better to have them in advance to do things right. Likely why some w123 cars Ive been in have good reception, and some have zero, especially on AM.

Fastlane: Brass Contact Spring Inside Front Bearing Grease Cap
http://catalog.peachparts.com/item.wws?sku=201547008502






.

[RichardLSU]

Should you replace the wheel bearing seals at the same time?

Is this the right part?
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1985@@1985&makeid=63@@Mercedes-Benz&modelid=6209%3AED|10000134%3AMBC|1510@@300SD&catid=241387@@Driveshaft+%26+Axle&subcatid=241454@@Wheel+Seal+-+Front&applicationid=W0133-1641523@@Wheel%20Seal%20-%20Front&mode=PA

[whunter]

Originally Posted by RichardLSU

Should you replace the wheel bearing seals at the same time?

Is this the right part?
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1985@@1985&makeid=63@@Mercedes-Benz&modelid=6209%3AED|10000134%3AMBC|1510@@300SD&catid=241387@@Driveshaft+%26+Axle&subcatid=241454@@Wheel+Seal+-+Front&applicationid=W0133-1641523@@Wheel%20Seal%20-%20Front&mode=PA

only if they are damaged.

[RichardLSU]

The hubs without the rotors slide on just fine, but once I put the rotor on the hub it won't go all the way on enough to put on the spindle nut. I can't figure it out. Nothing is scraping or hitting it just won't go on there. What am I doing wrong?

[vstech]

with the rotor on, the assembly is heavier. ya gots to wiggle a bit to get the large inner seal to fit over the rim and seat.

[eatont9999]

Thank you Roy. I appreciate this write up. I did this job along with rebuilding the front calipers on my 300SD this weekend. So far the results have been positive and no abnormal conditions have presented themselves. 3 Days of daily driving have occurred.

A few things I did differently are:

I used a dial caliper to ensure bearing play is less than or equal to .003" It was a little difficult to measure with the rotation of the rotor and the caliper on the pinch nut but I am confident that I was able to get an accurate measurement.

I did not use locktite on any bolts. I would have but I could not locate my bottle after I started the job. Hub bolts were tightened to 85ft/lbs, though.

I did not use that radio interference thing, either. It was not there to begin with and I felt not like figuring out how to add something I did not need. Same with the replacement pinch nut bolt. I saw no reason in changing it.

For punching out the bearing races from the hub, I used a socket of fitting size for the smaller race. The socket had a 2" extension on it and three blows from a 3lb sledge took the race out rather quickly. The larger, inner race, was a bit more of a PITA to get out. This is where I suggest a large punch. I used a small nail punch, which not only ruined the punch but took a lot of effort not to smash my fingers against the hub while holding the punch. Had I not forgotten, I had a large punch stored in the toolbox of my truck, I would have used it. There was some marring of the hub but not in the race seating area. I checked this out of concern. The marring from the punch is not in a contact point with any moving parts, so I am not fretting it.

PP sells tubes of wheel bearing grease marketed by Febi. I bought two of these and used one per side to pack the bearings, fill the center (not completely) and add some extra into the hub cap. Some grease was wasted as excess from packing the bearings.

If your wheel bearings are in known good condition and you are replacing them for preventative maintenance, a lot can be learned by checking play and ease of rotation of the hub before dis-assembly. You will want to aim for the same feel.

Correct me if I am wrong as this is my first wheel bearing replacement. I am still learning.

[gatorblue92]

Very helpful thread. My 280E needs new brakes and I have been hesitant to tackle them because I am always worried about setting the bearings properly. Good info here.

[Zulfiqar]

I think its best practice to regrease the bearings every 2 years or yearly if you live in damp areas. The exact weight of grease can be done without problem if you use a baggie for it, dunk the bearings in them and work the grease in the baggie, remove bearings install them, and then cut a slit in an edge and fill the hub with the remainder of whats in the baggie.

For adjustment, best is to use a dial gauge.