w123 brake pad replacement advice - PeachParts Mercedes-Benz Forum

asti84 · #1 12-30-2002, 01:13 AM

I've read both Jim Smith's post and the DIY for the W124 on the forum...i have a question about the bleeding portion of the pad replacement. I'm just going to try to replace my front pads... Is it necessary for me to bleed the whole system when I replace the pads or is this a whole different evolution?(Jim Smith mentions the bleeding of brake fluid but the DIY on the forum does not.) Sorry for the confusion but this is my FIRST brake job but I gathered courage from Larry Bible's comment on the easiness of this job. Thanks for your help.

1984 300 DT

Ken300D · #2 12-30-2002, 07:03 AM

In my opinion its only necessary to bleed the front brakes. However, you can do some good for the car if you go ahead and bleed the rear brakes to flush out the old fluid. It gets pretty nasty over time with contaminants like water and rubber particles. These contaminants shorten the life of your brake system parts.

Ken300D

jcd · #3 12-30-2002, 07:39 AM

Ken is correct. As long as you are into it, bleed the whole system. Setting up is the hardest part of the job.

Remember, hit the bleeder valves with penetrating oil.

JCD

JimSmith · #4 12-30-2002, 10:32 AM

asti84,

Glad to hear my post is still of value. Brake fluid is cheap and the general recommendation by Mercedes is to replace the fluid once every two years. All of it. I typically change the fluid with every pad change, which happens much more frequently on the front than the rear. When you change the fluid you will see it is very dark compared to the stuff coming out of the new bottle. I use Catrol GT LMA fluid only, and have had brake systems last over 250,000 miles regularly, with reasonable fluid change intervals.

Openning the bleed screw to aid in pushing the pads back into the caliper has proven to make the job much easier and avoids pushing that discolored, dirty fluied into the system. Good luck, Jim

kerry · #5 12-30-2002, 01:12 PM

While you may wish to combine brake bleeding with pad replacement, there is no necessity that you do both jobs at the same time. Replacing the pads can be done independently of bleeding the brakes and can be accomplished in less than half an hour once you are familiar with the procedure.

asti84 · #6 12-30-2002, 08:25 PM

I appreciate all the input from everyone...I will get the pads, fluid, paste, sensors, tools from a europarts store tomorrow and will update you on my progress...Again, thank you to all...and A Happy new Year!!!

The Warden · #7 12-31-2002, 12:34 AM

I'm just wondering, but now that it's been brought up, in every manual I've seen, it's been said that the brakes need to be bled as the final step in replacing brake pads. What is the reason for this, besides replacing the fluid? I've done brakes on a few vehicles, without bleeding the system, and haven't had a problem...the pedal's always felt exactly the same.

Also, how much fluid usually comes out when you do a complete replacement? I suppose that fluid replacement is something I should do at some point, probably when I do my brakes (that needs to happen PDQ; I've put it off way too long)...

Thanks!

240 Ed · #8 12-31-2002, 02:59 AM

Well, there is no need to bleed the brakes...other than the safety aspect.

I am not going into my standard lecture on brake fluid here, you can do a search, etc.

Suffice it to say though, that the longer the fluid is in the system, the more water it absorbs. Brake fluid loves to take water out of the air, and no, your system is NOT sealed.

The more water suspended in this fluid, the more risk of fluid boil out of this water. IOW, it makes steam! which is a rotten hyrdrualic fluid!

IOW, you get massive brake fade-NO BRAKES!

engatwork · #9 12-31-2002, 06:14 PM

Another thing you will see and need to be aware of on the W123 cars is that after you replace the pads the pedal will initially feel "spongy" until the pads "seat" in good. I don't have a clue why they do this so after you bleed the brakes a couple times and are convinced the air is out of the system they may initially feel a little spongy.

sublettm · #10 12-31-2002, 07:44 PM

Quote:

Brake fluid is cheap and the general recommendation by Mercedes is to replace the fluid once every two years

I was reading my fathers Mercedes Service Manual over the Christmas holidays and it states that the brake fluid should be repalced ONCE A YEAR. My father and I did three of our 123's while I was home and it really didn't take long at all. We consulted with his mechanic and he told us the best way to replace the fluid is to open up all four bleed valves and keep adding fluid to the resevoir until you have clean fluid coming out of all four valves then close them up. If you do it this way, you won't have to bleed them at all since you haven't let any air into the lines. You will have to bleed them if you aren't careful and let the resevoir get too low and introduce air into the brake lines. All said and done, it only took about two hours to do all three cars.

Mike

asti84 · #11 01-01-2003, 02:28 PM

I called the local Europarts store here in Orabge County (Newport Beach) and I asked for OEM brake pads and the guy said he doesn't carry any of the "German Stuff" because they create too much brake dust and eat up the rorors too fast. They are bad enought that" his customers wanna shove it up youknowhere..." He sells PBR brake pads made in Australia. Has anyone used this brand? Please advice. Thanks.

240 Ed · #12 01-02-2003, 07:52 AM

The brake pads I favor have been "Metal Masters" from Australia. You never know about these names, and the same pad might be "brand-marketed".

I think this parts guy had it wrong. The way I see it, Mercedes made a choice about brake pads. They chose to eat up the brake pads (thus, creating a lot of dust) rather than putting more metal in the pad (Which eats up more of the rotor, but gives you more fade resistant brakes).

The soft pads give you a more immediate bite, but are quicker to fade. Probably a fair choice for most driving in urban/suburban life.