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Replacing Brake Rotors?

Started by mineson, 20 April 2006, 12:04 PM

mineson

Hello All,

I want to replace my front brake rotors on my 1977 450 SEL, and I'm not sure if I have to remove the hub or the bearings.  I've read the service manual (42-220) as well as the brakes section in my Chilton's manual, and they're not very explicit on the necessary steps.  Hopefully, the forum can shed some light on the subject.

Question 1) Can the rotor come off without removing the hub?  I know it can be done on the w140, but I doubt it on the w116.

Question 2) If I have to remove the hub, do I have to replace/repack/adjust play on the bearings?  Replace and Repack isn't so bad, but there is a  >:( special tool >:(  required for holding the gauge to adjust the play. How important is that to get right?

Question 3) Both manuals say I need use new "Self-Locking Hex Socket Bolts" to hold the rotor to the hub.  I can't find these for sale anywhere, but I don't really know what I'm looking for.  Is this just a lock-washer under the head, or is it a special type of bolt?  Can I use the old bolts with Locktight?

Queston 4) Should I let a mechanic do this one?  I'm comfortable doing work like this, but I don't have a shop or any special tools.  Is this job out of my league?

Thanks,
-Matt

Denis

Hi Matt

I am an old-timer at this so here we go  ;D

Question 1 : Yes, you need to remove and suspend (from an improvised hook) the brake caliper, then you can remove the fasteners that hold the disk to the hub.

Question 2 : Not an applicable problem (see above) but it makes sense to adjust (or even repack) the wheel bearing at this point - you have taken all the stuff apart so why not do it ? The proper tool is a dial caliper with a magnetic base, and yes : you can do it by feel and a bigger yes : it is better to adjust it to spec. I am as obsessed with this as Nutz is about air filters (forum joke)  :D ...but, dear Matt it is NOT necessary.

Question 3 : Unless mangled, YES you can use the old ones with Loctite - the stealership has them but try to preserve their nerves - they already hate you for not buying a new car  ;)

Question 4 : My opinion  ::) my opinion  :P - do it yourself !!! no special tools are required and YOU can make SURE that it is done correctly.

But you must do certain things for safety reasons :
The caliper bolts are locked in position with tabs from a metal plate located behind the bolts. The plate actually spans teh distance between both bolts. To remove the bolts, you must use a punch to flatten the tabs near each bolt on the plate, then the 19mm socket fits. When you re-assemble, you can reuse the plates if they are not damaged, (cracked) but do so with Loctite OR use new plates (and loctite), YES I like Loctite called "frein-bloc" in France (made by Loctite in northern France).

Voilà monsieur Matt

Hope this helps.

Denis

Paris, France

PS - anybody in Europe wants to buy a LOVELY 350SE, I know of one, please email privately -no, not mine, it is nice but not "lovely" (yet)

michaeld

Mineson,

It has been rumored that Denis was the man who came down Mt. Sinai - his face still aglow from the Divine Shekinah glory - bearing the w116 specs on two iron tablets (stone for law, iron for autos?).  If Denis says it, it must be true! 

I'm going to be doing brake work pretty soon myself, and everything Denis said conforms to what I've read in prep for the job.  If you have the service history for your car, you can see when the last repack was done; otherwise, you might as well just do it given that you've already done 90% of the work anyway just by the disassembly you've already done.

I have been saving and acquiring nuts, bolts, washers, seals, o-rings and whatnot for some time.  Harbor Freight sells a lot of this stuff online - and often times ONE bolt is more expensive than a set of 1000.  Before I do a repair/maintenance job that I haven't done before, I get a book (or go to the library) and read up on it to decide whether I can do it, and what kind of tools I would need.  Haynes and Chilton both make fine manuals dedicated to disc brake repair.  If I decide the job is within my capability, I would much rather spend my money on tools than on someone else's labor. 

In my area, the two cheapest places for tools are Harbor Freight (which also sells online) and Home Depot (which has a "Craftsman-like" lifetime warranty).  I LOVE tools!!!  If you aquire a good set of them, and learn to use them, you will be way ahead in the long run.

Another thing I would recommend if you are unsure about what you are doing is a digital camera.  You can use it to take "before and after" pics for assembly/disassembly/reassembly purposes, and you can also post pics to the forum if you need specific help "getting this particular #*!^$* bolt off."  A pic is worth a thousand words, as they say.

Good luck on your brake work.  Let us know how it goes for you.
Mike
 

s class

You can replace the front rotors in a Saturday morning if you are reasonably handy. 

1.  Dismount and suspend the front calipers as described above.

2. Prise off the grease cap in the centre of the hub

3.  Withdraw the split pin and remove the crown nut

4.  Withdraw the rotor and hub assembly.  Take care not to introduce dust and dirt into the wheel bearing.

5.  Inside the rear of the rotor are 5 allen head bolts securing the rotor onto the hub.  These need to be removed - they are very tight and usually loctite-ed.  Here's a trick.  Bolt the hub assembly back onto the inside of the road wheel.  THis way you have the tyre to hold onto.  Get a helper to hold onto the tyre (lying face down) while you remove the allen head bolts.  You will need an allen head socket, extension bar and a breaker bar with like a 4ft extension.

6. Reassembly is the reverse of disassembly.  WHen mounting the new rotors onto the hubs, use loctite and be sure the mounting faces are clean and free of rust/dirt as this could cause untrue mounting leading to rotational run-out of the rotors.  WHen reassembling the wheel bearing, repacking is a good idea.  Be careful not to hurt the oil seal lips when fitting the hub assembly onto the stub axle.  Correct torque and clearance on the crown nut is critical to wheel bearing life and performance.  I generally do this by feel and experience.  There should not be any lateral play in the bearing, but it should not be so tight as to increase the turning resistance.

Hope this helps,

Ryan in South Africa


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Denis

Hi fellows

Sorry for my incomplete post, Ryan is absolutely correct ! you need to remove the bolts from behind  >:(

My apologies....still, buy a dial gauge and a mounting base and set the bearing to specs.

Denis

Paris, France

mineson

Thanks Denis, Ryan, Mike and Everyone else who might reply for such great advice!   ;D

It's exactly the clarification I need to be confident before doing this work.  I would have had more of an update for this post, but it rained all weekend long so I had to defer the start.  The good news is that it gives me a chance to ask some more questions.

I'm going to repack the bearings since I doubt they've ever been done and  I'm 95% sure that's where most of my noise problem is.

Symptoms:
The symptom is a loud, constant, speed-sensitive rumble coming from my front passenger wheel.  It sounds something like the tire is rubbing the wheel-well, or the tire is muddy, flat or for off-road.  After replacing the steering linkage, balancing the wheels and a professional alignment, the noise is still there.  There is also a slower vibration felt in the pedal when braking, and when I did my tie-rods a few weeks back, I saw a crack on the rotor. 

The Plan:
Since I've got a set of rotors and pads on hand, and that crack has to go, I figured I'd replace the rotors and see what that did.  I normally would only attempt one thing at a time, so I wanted to do the rotors one weekend, then the bearings the next.  I now realize that this is doubling my effort, and I should really do both jobs together.

I'm not that worried about repacking the bearings, but I want to make sure I have everything I need to finish the job correctly before I disable the car. I repacked the bearings on my '86 Ford Van when I did its rotors, and I remember the principle was easy enough (although refreshers and pointers are always welcome), but then everything on my Benz has proven 2-10 times harder than any other car I've worked on. (I have no complaints since it's also 10 times the quality of any other car I've known  ;)).

The MB Service Manual lists five special tools for the job, but I've decided to find a "dial gage and setup" to check the play (I have a question on this below).   

Finally, as a visual companion to your advice I will follow this tutorial for repacking the bearing s on a w123 which seems applicable to the w116.  http://www.diymbrepair.com/Maintenance/Bearing/

Questions:
Question 1)
How do I know if I should replace the bearings vs. reuse the existing ones?  I'm replacing the seal, but if the bearings might need to be replaced, I'd rather just plan on doing it.  However, if they can be restored to good-as-new with a new pack, I'm OK with that too.  What would be the sign that they're shot?  Given the rumbling noise, what's the likelihood that they'd need to be replaced?  Since the full set costs $30 on e-bay or $70 from an online store, it seems like a reasonable 'better-safe-than-sorry' part to replace while I'm at it.

Question 2)
What is a dial gage, and how do I use it?
Is this a correct example http://www.brassandtool.com/Dial-Indicators.html ?

From what I can imagine, it would be a very accurate depth/bore meter with a magnetic rig that will hold it firmly where you put it.  I would put the magnet on the rotor, and set the pin of the gage on the end of the front axle, and tighten it in place. Then I would stand with the axle pointing at me and push and pull the rotor to measure how much it moves.  Specifically, I want to make sure that I'm not supposed to be checking up-down or left-right or side-to-side play.  I'm just checking the travel on-and-off the axle shaft, from closer to the engine to further from the engine.  Is this correct? 

Question 3)
If I had to adjust the play by feel (this dial gage is hard to find…) would I just make it as loose as possible without any wiggle?


Question 4)
The MB manual suggests two more tools...  (1) a Hub Puller and  (2) an Inner Race Puller.  The first was recommended for removing the hub from the axle, which I assumed would pop right off since it should be filled with grease.  The second was because the inner race could be stuck on the axle pin once the hub is pulled off. Should I worry about this actually happening?  Has any of this ever happened to anyone?  If so, how did you eventually resolve it?

Thanks Again!

-Matt

Papalangi

Here's a link from a bearing manufacture,
http://www.timken.com/industries/automotive/autoaftermarket/techtips/VolumeIIssue3AupsFinal0104.pdf#search='check%20wheel%20bearing%20dial%20indicator'
Dang, that's a long one.

Here is another,
http://www.carcraft.com/techarticles/81298/

Go to http://www.harborfreight.com and search for "indicator" and also "magnetic base".  Don't get the base with the little adjusted gizmo in one of the arms.  It will just piss you off.

Michael
'83 300SD, I'm back!  It's the son's new car (12/2020)
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023
1976 280C
1970 250/8

Denis

Hi Mineson

Mercedes are not harder to repair than other cars, they are just different. In my experience, they are much easier to repair than say, a VW and infinitely more than a Renault or Citroen.

A rumble that increases with speed is bad news : typically failed bearings that cannot be fixed with new grease.

If you do weekend jobs with some time to relax (like me), just do one side at a time.

Yes, that is the correct tool. That is a bit expensive, even by Euro standards, I paid 45â,¬ in France. Typically they come with instructions but you have the general idea. But why use them if you can do it by feel ?

You referenced article is perfect but it says :

QuoteThe factory manual suggests checking end play which is if you push then pull on it; it should move less than .02mm. While I haven't scientifically figured out where this point is I figure it is when you push and pull on it and hear nothing. If it is a little loose you hearing the bearings move, if it is tight there is nothing but you feel the resistance turning


This is incorrect. he is "figuring", just "figuring". Mercedes bearings don't suddenly go from loose to tight : there is ...a bit tight, tighter, still tighter and tighter again, all this while the disk rotates without really binding or feeling all that different. The reason is that they use an adjuster that tightens infinitely on the spindle (shown in the referenced article) and not a castellated nut which is usually too loose or too tight...can you fell a difference of 0.02mm ? I surely cant, hence the dial gauge. You will not feel any side play, due to the taper used to position these parts. BTW, that adjuster is one of the joys of mercedes engineering - how many things mechanical do you know can be finely adjusted ? a Nagra (swiss made) tape recorder perhaps ?

In my experience (12 times), you can also drive the seal at the back of the bearing by placing it just right and using a mallet on a piece of wood to drive it in. Ryan's trick too loosen the bolts is a good one but I just did mine by putting the old disk in a big, big vise and in one quick tug, loosened the bolts with a 40 cm bar.

Good luck

Denis

Paris, France

s class

I agree with Denis.  Rumbling from the bearings is a sure sign they need to be replaced.  Once yo have reassembled the car and checked the bearing with your dial guage, I suggest you drive for a few km, and then recheck the bearing a things may have settled allowing the clearances to open up. 

Good luck, Ryan


[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Denis

Reading back this thread, an aside from my initial mistake, I dare say that there is more KNOWLEDGE in this post than can be found inthe heads of most mechanics. 

Stand proud fellows !

Denis

Paris, France

Denis

Sorry, it's me again but one final comment from experience :

you do not need a hub puller - just tug the hub off by holding the disk once teh outer bearing and fastener are removed. With a bit of luck, the rear bearing seal might even pop off when you pull hard - I have seen it happen a few times.

Denis

Paris, France

mineson

Thanks,

I have not yet started the work, and I want to know how "BAD" it is that I drive 20 miles (32Km) a day on it at speeds between 35 and 60 MPH (55-95Km/h). 

Quick Update and Question:

I've got everything I need now except for the dial gage.  The only place that had one that went to .0005 inches (.012mm) was at Harbor Freight.  I have learned that when ordering from Harbor Freight, one should call the 1-800 number to get the "Direct Shipping" option.   I ordered it on May 2, and now they say I'll get it by May 21!!!! :P 

How dangerous is the rumble?  Can a worn bearing burn/eat through the axle and cause the wheel to pop off or something terrible like that?  Should I be riding the bus to work until its fixed?

I would be OK with replacing the bearings now, then doing the job again once I get the tool.  I just want what's best for Mercy....

Thanks again,
-Matt

Papalangi

My '65 Mustang began rumbling, then there was a pop-bang-whump from the front.  The drivers side front corner dropped an inch or so and I passed my own hub cap.

This was East bound on the 520 just as I started across Lake Washington.  I slowed way down, waved to the heplful man that pointed to my car as if something was wrong and ground my way to the first exit.

I could feel the heat blazing from the front wheel and it looked wrong.

Turns out the outer bearing had exploded taking the hub cap with it.  The only thing keeping the wheel on was the fact that the washer under the castle nut had turned a groove on the inside of the hub.

Time for a new hub, drum, shoes and maybe a spindle.

Your mileage may vary.

Michael
'83 300SD, I'm back!  It's the son's new car (12/2020)
1976 450SEL, 116.033  Sold it to buy a '97 Crown Vic.  Made sense at the time.
1971 250C, 114.023
1976 280C
1970 250/8

mineson

Wow.   :o  Sounds like I'll be riding the bus until I do the work. :-\

Good news is the Dial Gage came today and the weather might hold out for the weekend, so I'm doing this tomorrow....

-Matt

mineson

OK Team,

I've successfully changed one Rotor, and these instructions were perfect!  Thanks once again.  ;D

Denis, I didn't have a lock plate on the caliper!   ??? I used heavy duty locktite (the red stuff) to be safe.  I'll get new ones since I have to redo the bearings soon....

Yes, I have to redo the bearings because the replacement bearings I got didn't fit!  I had to put the old bad bearings back on with a repack. :'(

The outer bearing looked fine, but the inner bearing had some marking on the race.  For the life of me, I couldn't get the inner race out of the hub... the exposed rim I needed to hit was maybe 1mm wide and I couldn't get it to budge.  Anyone have a trick on getting the bearing races out of the hub?

I bought Timken (made in USA) bearings which looked exactly the same and had the same part numbers, but once I packed them up and tried putting the hub on the axle it just wouldn't go on.  I eventually got the old outer bearing and the second new one, and tried them on the axle.  The old one slipped right on while the new one would get stuck.  Same went for the new outer bearing. The Timken bearings were a few mm too small.

So, I was forced to clean the old bearings and reuse them.  The old outer bearing had markings on the rollers similar to the race.  It looked like the imprint of sand on parts of the surface of the rollers.  I would have taken a picture, but at this point I was quite frustrated, covered in grease, and likely to distroy any electronic equipment I encountered.  Once I replace the bearing I'll take a shot for all too see.

The good news is that a repack did a lot of good and the rumble went away.  However, it's only a matter of time before it fails again so I need to find the correct bearings. Does anyone know which bearing manufacturers will really fit on a 1977 450SEL 4.5L?

-Matt