Doing the brakes for the first time on my 240D

[Crazy_Nate]

Car is in the signature.

I'm gonna put all of my questions in one place, as I have a few...

This is my first time doing the brakes on any car. I have tools, and I'm competent, but still in the learning process. I'd like to change the brake pads, rotors, and flush the brake lines. When I bought the car (December '07), I had to pass the safety inspection for the state of MD. The brakes passed fine, however, the rotors were on the thin side (I guess the PO had them turned). The independent mechanic that I had do the tie rods and valve adjustment / fuel filters said they'd need to be done within 5k miles. I'm not a frequent driver, having barely gotten 2k since then...however, there is a bit of a cyclic rattle / scraping sound on the front right brake - like it makes a sound once every revolution. I believe it's the brake, because it doesn't make a sound when I apply the brakes (the car brakes fine...verified by two independent mechanics). Maybe some type of runout on the rotor? Irregardless, it drives me nuts and I'd like to fix it. If I change the rotors and pads, it should go away, right?

So far as I've heard, there are two types of calipers on these vehicles, ATE and Bendix. What's the easiest way to tell them apart? Is there anything that is specific to either system?

The parking brake pretty much...doesn't work. I want to fix that too. Currently, you depress the petal, however it doesn't engage. I've tried at moderate speed (20 mph) and I can't even feel it. Which parts should I be replacing? The fastlane parking brake shoes have additional hardware, so that looks good. Should I pick up new cables for the brake? Which ones should I get..?

Continuing on...I haven't the foggiest idea of what to look for when purchasing pads or rotors. What's the difference in the discs on fastlane? I don't think I need vented rotors in the rear, but, why the large difference in price for the fronts? Any quality differences? The rears seem to be very close in price...any difference there?

Pads...I haven't the foggiest. I don't drive much...and I don't use my brakes a lot, when I do, however, I like responsive brakes. No clue what to look for here.

Are there any parts I should change while I'm in there? Pins, springs, bolts, etc?

When I bleed the brakes, how much fluid will I need? The 3/4 liter container (DOT4) looks like plenty, however I have no idea.

From what I've read bleeding is a two person job. Start at the furthest brake, start to bleed and have the other person "pump the brake pedal" until it comes out clean...then move to the next brake? Do you constantly add new fluid to the reservoir as the you bleed the brakes? What's the best way to catch the old fluid? I have a feeling it's gonna be pretty naasty.

What kinds of tools do I need? I've got a full set of wrenches, sockets, access to an impact wrench (impact sockets, maybe...I'll buy a couple if I need to), floor jack and jack stands. I'll probably have a torque wrench by the time I get the brake parts in. Which range (of torques) would be appropriate for this job?

If there's anything I've missed, feel free to point it out (especially if you have little tricks to make the job easier). Also, if somebody has described how to do this in a post, and I've missed it, point me there and I'll read up.

Thanks for the help!

[techguy512]

Originally Posted by Crazy_Nate

What kinds of tools do I need?

Rear pads and rotors are easy to do. Fronts require disassembly and repacking of the front wheel bearings. Be prepared for that.

Click the "Buy Parts" link, and follow it to the brake section for your car. If you then click on "calipers" you'll find photos of ATE and Bendix calipers. The easiest way to tell them apart is by the pad retaining clips. ATE uses flat clips, and Bendix uses formed wire. Look at the photos and you'll see the difference.

Take some time to collect the FSM sections detailing the various steps in the job. Understand them well before starting, and you should have little or no trouble.

[Crazy_Nate]

Ok, so, I'm gonna need a dial indicator for checking the bearings...

Anything else I'll need while I'm perusing MSC-direct?

I'll probably get this indicator set: http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=1755500&PMT4NO=0

Where do you get the bearing grease? Dealer?

[techguy512]

Originally Posted by Crazy_Nate

Where do you get the bearing grease? Dealer?

Mobil1 synthetic. Get it at any McParts.

[vstech]

the good synthetic disc brake bearing grease is great.
just use it.
I think you will need at least two bottles of brake fluid.
get some BLUE loc-tite for the bolts on the rotors, and the calipers.
clean the bolts very well with a wire wheel, or at least a wire brush.
clean the area the pads slide in so it is free of debris you should see clean metal there. some say you should lube this area, but I dont think it's a good idea.
have fun, and be safe, use a pair of jack stands, and be sure and lock the wheels that are on the ground with good chocks!

[Crazy_Nate]

What size are the hex sockets for the front disc hex socket bolts? Do I need new bolts?

The files I've been reading say both the hex and hex-socket bolts are self-locking and one time use only. Fastlane has 'Brake Caliper Bolts' for front caliper mounting...that doesn't sound like what I'm looking for...

Thanks!

FYI: These are the documents I've been reading
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Chassis/42-220.pdf
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Chassis/42-228.pdf
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Chassis/42-010.pdf

All here: http://www.pauldrayton.com/uploadfiles/merc/Service/W123/Index/Groups/42BrakeSystem.htmlv

[barry123400]

Since you quote this is the first time doing brakes on any car including rotors. Remember many rotors if not all come with an anti rust preservative on the machined surfaces. You should clean this off with brake cleaner just before installing the new rotors. You may already know this as well as a few other things mentioned. So this is a just in case type of thing.

If you really want to do a good job replace those old rubber brake hoses as well as a preventative type of thing. Especially if you think they might be the old originals. Not that pricy either. I for general use preffer an organic replacement brake pad set. Less agressive wear on the rotors and your brake system was designed for them. These are also in general less expensive than metallic type pads. You do not have a race car on your hands with that 240d remember.

Also when prying back the original pads off the old rotors try to establish that the pistons in the calipers are still pretty free and the pistons slide backwards into their cylinders without a tremendous amount of effort. Remember each caliper has two pistons and two cylinders. Most cheap cars including some expensive ones only have one piston and cylinder per caliper.

They may call the hub to disk bolts one use. It is thought that is because of an original coating to lock the bolts in. Use blue locktight on the old bolts. I think almost everyone reuses them. I believe both brands of calipers are interchangeable. Mercedes just used two suppliers.

If you do need new calipers this might allow you to buy the ones most cost effective. Check this out if it comes to it. One brand is a lot more than the other or not as easily available sometimes.

[Crazy_Nate]

Ok, so, suppose I do want to change out those hoses...I just need two for the front, and two for the rear, correct?

Am I going to have to drain out all the fluid? If so, is it as simple as refilling the reservoir and letting the air out? I can always get a big container of brake fluid.

[mobetta]

when I called the mobil 800# they could not confirm their grease was ok for disc brake wheel bearings. so I use valvoline synthetic.

easy one man bleeder- can use a bike pump, etc . keep it under 15 psi

[Crazy_Nate]

That could be pretty helpful...but, it might be in my best interest to have a second set of hands around...second brain, too. I'll probably pay one of my grad. student buddies in beer and he'll be more than willing. If two mechanical engineers can't figure this out...well...

So, that thing just goes on to the reservoir and you pump it...cool. I'll probably give something like that a try next time I do the brakes.

[Stevo]

Originally Posted by mobetta

when I called the mobil 800# they could not confirm their grease was ok for disc brake wheel bearings. so I use valvoline synthetic.

easy one man bleeder- can use a bike pump, etc . keep it under 15 psi

My pressure bleeder uses the air pressure from the tire. Its gotta be one of the best tool investments that I've made.

Nate, do you have a shop manual? Haynes is good for brake work, good pics.

[Crazy_Nate]

Originally Posted by Stevo

My pressure bleeder uses the air pressure from the tire. Its gotta be one of the best tool investments that I've made.

Nate, do you have a shop manual? Haynes is good for brake work, good pics.

I have a Haynes manual, I don't have the CD for the service manual (is that the same one as the Paul Drayton uploads?). I have a laptop that I can keep next to me if I need to look at .pdfs

[Stevo]

Originally Posted by Crazy_Nate

I have a Haynes manual, I don't have the CD for the service manual (is that the same one as the Paul Drayton uploads?). I have a laptop that I can keep next to me if I need to look at .pdfs

http://www.pauldrayton.com/uploadfiles/merc/Service/Library.html

See if you can use this. I have the paper editions so don't go there much.

[300SDog]

Regarding the fluid flush, I'd start with driver's side front to flush out the master cylinder. Bein closest in line it'll save you millions of pedal pumps instaeda workin from passenger side rear. And then attack each individually after first flushing the MC from there.

[Crazy_Nate]

Is there a special way to do the fluid flush if I want to change the brake lines?