First brake job questions... - PeachParts Mercedes-Benz Forum

MercFan · #1 04-06-2007, 04:46 PM

Going to do a brake job on my 300D, front and back: pads, rotors and emergency brake in rear. Parts arrived today in mail and it all looks good. It was rather easy disassembling the rear brakes and taking the rotors off - I was glad to see how easy it was. Now we're getting ready to assemble new parts.

Questions:
1) Should I clean the new rotors with parts cleaner or otherwise before assembly? They are very sticky...

2) Going to replace the emergency brake shoes and springs - any words of advice there?

3) Anything else to consider before starting the assembly - like I said, it looks pretty straight forward so if there's something special that may not be obvious let me know.

thanks,
james

toomany MBZ · #2 04-06-2007, 04:59 PM

Rotors and pads, pretty easy. When pushing out calipers, do one at a time, so as not to push other side out. Do clean rotors with brake cleaner before using. I spray after installed, you'll get grease on 'em. Thinking sticky stuff is a sealer of some kind, I would make sure that is removed. The rest, let us know how the emercy change goes. I don't know if you need a special tool or not, as they are in the hub and not eaisly accessed. Happy wrenchin'.

winmutt · #3 04-06-2007, 05:17 PM

I bought parking brake pads but cant for the life of me figure out how to get the springs off without the mb tools. Suggestions? Never in my life changed drum brakes.

P.E.Haiges · #4 04-06-2007, 06:58 PM

MercFan,

Yes, clean the rotors. Gasoline is the cleaner of my choice.

I would replace the adjustor (the part with the threads). If old one rusts solid, its impossible to adjust the parking brake shoes and makes it difficult to get the rotor off next time.

I made a special tool by form grinding a 1/4 inch square screwdriver. It made it much easier to replace the springs.

I'm sure Toomany MBZ meant to push out pads, not calipers. Since U have the calipers out, replace the pads before replacing calipers. U might have to file the caliper surface or steel sides of pads so there is a slight clearance so the pads can move freely.

toomany MBZ · #5 04-07-2007, 04:42 PM

Quote:

Originally Posted by P.E.Haiges

MercFan,

Yes, clean the rotors. Gasoline is the cleaner of my choice.

I would replace the adjustor (the part with the threads). If old one rusts solid, its impossible to adjust the parking brake shoes and makes it difficult to get the rotor off next time.

I made a special tool by form grinding a 1/4 inch square screwdriver. It made it much easier to replace the springs.

I'm sure Toomany MBZ meant to push out pads, not calipers. Since U have the calipers out, replace the pads before replacing calipers. U might have to file the caliper surface or steel sides of pads so there is a slight clearance so the pads can move freely.

Yes, meant pads. Better not be a "senior moment", dang it. I have a tool quote from Phil on these, haven't proceeded. I have changed out drum brakes, yet on an American car that had easy access, still could have used a special, albeit cheap generic, tool. On these cars, you have to work through the lug bolt holes... just another hurdle.

tobybul · #6 04-08-2007, 12:21 AM

You'll need to press in caliper pistons when putting in new pads as they will be much thicker than the used pads. Best tool for this is a C-clamp which you can also use for other things later. Don't bother with special tool for this.

ALso, make sure the brake resernoir is not full when pressing calipers in otherwise fluid will overflow....

vstech · #7 04-09-2007, 03:34 PM

I have changed calipers, and pads on my MB's and I have never needed anything more than a large screwdriver to compress the pistons.
a C Clamp is nearly useless on these dual piston calipers. there is noplace to put the clamp... a screwdriver works flawlessly, just pry against the old pads until the piston is in it's home, and pop in the new pads.
done.
open the bleed screws and let any air out. while you're at it, suck out the old fluid from the Master cylinder fill with fresh fluid, and let the lines flow fresh fluid into the caliper. solves future problems!
John

Goatspunk · #8 04-09-2007, 05:55 PM

Always do one at a time, so you have a second to look at when you get lost. Especially with the drum brakes.

MercFan · #9 04-15-2007, 10:05 AM

Well, finally had a chance to work on the brakes this weekend - replacing all rotors, brake pads and a new parking brake set on old Hansi. Dad and I worked on it all Saturday and we're almost finished (3 out of 4 done, resting on Sunday). Here's a recap:

Started on the rear passenger side. Pulled off the wheel, caliper, old disc and started disassembling the dreaded parking brake. It looked pretty daunting with all the parts and springs in there, and it was... it took us a good 4.5 hrs to disassemble and rebuild the first wheel... After re-assembling the parking brake nightmare we had a heck of a time pushing the new rotor onto it... after some time of cussing and trying in vain, my dad discovered that we had installed the brake shoes on backwards! That's right -word to the wise: make a good mental note on how these parts fit initially when working on these shoes as they have different notches on top and bottom that you have to assemble just right. Funny thing is that it will go on backwards just fine, you just won't be able to push the rotor back on it... that's how you know

The upside was that with all the practice, we were able to disassemble and reassemble the parts properly in about 15 minutes! I was pretty amazed how quickly it went once we knew the in-s and out-s of the spring assembly. BTW, all we used was a big screw driver, a small screw driver and a pair of needle-nose pliers to pull the springs in and out of the proper places. The trick is figuring out and visualizing how they fasten in place. Once you have the mental image of it it's pretty easy.

All in all - we did the first wheel in about 4.5hrs, and the whole second rear wheel in less than 45 minutes - it was really very simple on the second wheel. No problems whatsoever.

We moved on to the front passenger wheel. Again we pulled off the wheel and the caliper. Pulled off the grease cap and removed the outer bearing. Had to use PB Blaster and an Impact wrench to separate the old rotor and the assembly that holds the inner bearing in place (not sure the name). Came off pretty easy - we did NOT touch the inner bearing as I didn't want to damage the seal ring (didn't have a replacement). Repacked the bearings with Valvoline Synthetic grease and reassembled with new pads in place and new anti-rattle springs. Used C-clamp and a small pry bar to push the caliper pistons back into place - it worked really well. Reassembled it all putting some anti-seize on some of the key bolts. So 3 of 4 wheels are ready - the forth one should be easy. All it all - it was a very satisfying experience despite some initial setbacks! Still got some paring brake adjustment to do - I can't wait to drive it.

One last question - do you all think that it will be necessary to bleed the air out of the lines? Did not have to crack them open at all, just removed some fluid out of the top of the reservior to prevent overflow...

biobenz240d · #10 04-15-2007, 10:51 AM

I always take a few digital pictures of anything I disassemble so I have a few pictures to look back at. You might have a shim or washer and not be sure where it went. Works for me.

sokoloff · #11 04-15-2007, 11:04 AM

Just an FYI from the manual. You should not mix different types of wheel bearing greases and they call for a specific amount. Without looking, I want to say it's about 65 grams per side. Overpacking is as bad as underpacking. A dial indicator is also called for to set the bearings if you want it to be exact. Many people don't use the dial indicator and probably get it close to spec.

P.E.Haiges · #12 04-15-2007, 03:07 PM

MercFan,

It should not be necessary to bleed the brake systemas long as the level in thr brake resorvior was always above the outlet.

P E H

JimSmith · #13 04-15-2007, 05:13 PM

It is beyond my comprehension how you can do all that work and skip changing the brake fluid. Chances are it is black inside the caliper, and is no longer chemically able to be meet the criteria to be called a low moisture absorbing fluid. And once the fluid starts aborbing water the steel surfaces inside the caliper begin to corrode. Thus the black color of the fluid.

The manual calls for changing the fluid every two years, and recommends this time of year for the event. Brake fluid is cheap. I use Castrol GT/LMA DOT 4 fluid. Costs at the most about $5 to change all the fluid in the system, except the clutch line. And, it is relatively easy if there are two of you.

Sounds like you are doing a bang-up job. I remember replacing the rear discs on a 1982 240D years back. I didn't touch the emergency brake shoes, other than to adjust them inward, and the thing still required some hammer blows to get it on, but it worked fine once installed.

Jim

dannyF · #14 05-02-2007, 07:12 AM

Is there a special MB bearing grease that should be used for repacking? If so, i there a source or is any halfway decent bearing grease just as good?

vstech · #15 05-02-2007, 08:32 AM

I second the notion, that not changing the fluid with all that work is a bad idea.
while it's not needed to BLEED the air from the system, it is a good idea to drain out the old fluid and replenish with fresh fluid!
and on this vehicle, it is SO easy. just fill the resivoir with fresh fluid, keep it full while you open one bleeder at a time. that's it. when one bleeder starts flowing clear, close it, and move on to the next one. done.
also, a tip for those of you worried about the inner bearing on the rotor.
first take out the outer bearing, set it in the hub cap, next put the spindle nut back on, now, pull the rotor up against the spindle nut, and give it a solid pull, and the inner bearing and seal will pop right out, no damage! clean out all the old grease, repack the bearings, and reinstall. no need for a new grease seal if your old one was not leaking!
John