Brake booster: replace it or wait? - PeachParts Mercedes-Benz Forum

Chad300tdt · #1 02-15-2008, 10:10 AM

I am collecting all the parts to do my brakes. 4 loaded reman calipers, 4 new hoses, 4 new rotors, reman master cylinder, new reservoir seals, and new reservoir cap.

I can get a reman brake booster for $54.97 after I return the core. Is it worth replacing it while I'm doing the master cylinder since I can get it so inexpensively, or should I leave it alone and wait until it needs replacing?

Also, all my hard lines are fine, but is there any other suggestions of things I should consider replacing? (sensors, etc.)

dieseldan44 · #2 02-15-2008, 10:14 AM

For $54 id do it. Its really not bad to replace at all. Four bolts that are tricky to get to under the dash, but not bad with a universal extension.

You have to bleed it obviously anyways, might as well do it all up right instead of having the booster go out in 6 months.

Good luck,
dd

Chad300tdt · #3 02-15-2008, 10:20 AM

That's how I've been leaning ... however, my "replace it while I'm in there" mentality has lead me down some long roads before.

Chad300tdt · #4 02-15-2008, 10:25 AM

Also, does anyone see a benefit using slotted rear rotors? I'd think it would be more effective to have them on the front, but I see they are only available for the rear at Fastlane.

dieseldan44 · #5 02-15-2008, 10:29 AM

Quote:

Originally Posted by Chad300tdt

That's how I've been leaning ... however, my "replace it while I'm in there" mentality has lead me down some long roads before.

Im the same way. This will not be one of those roads (and Ive been donw a few thus far!!). Its four nuts and out it comes. Nothing easy to break, nothing to mis-align, etc. The work in replacing it is moving all the other stuff out of the way that you have already moved :-)

To get to them I used my 1/4" drive socket with a 6" extension and a universal. I think the nuts are 13mm. I put my head under the brake pedal and guided the socket onto the one trick nut that in the upper left.

One of those magnetic holders that goes inside the socket to hold the nut is useful but not imperative for re-assembly. Don't over tighten the nuts - FSM i think had them as 15 nM or less. Youll notice they wont be too tight to begin with (unless a PO or PO's mechanic ignored it once before :-) )

Chad300tdt · #6 02-15-2008, 10:35 AM

Cool info, thanks for the insight dieseldan44.

You read my mind about the possible problems I was imagining.

my123ca · #7 02-15-2008, 11:21 AM

Since you will be replacing the rotors and calipers. I would have used the front vented rotors and calipers from an SD. It last longer and resist warping. I have never tried the slotted ones in front but I have the drilled ones in the rear. They are OK.

Chad300tdt · #8 12-02-2008, 07:48 PM

UPDATE: I ended up waiting to see if the booster would last. Well it lasted until about a month ago. It's now pulsing when the brakes are applied gently and still fine when I apply the brakes with authority.

It feels like I have ABS when the pulsing happens.

Anyway, I have the new brake booster in my hands and will be installing it tomorrow afternoon. I'm guessing it will take about an hour to have it ready for a test drive ... less time if I'm lucky.

my123ca, I did end up using 1st gen. 126 calipers and rotors for the fronts.

I also ended up buying a 1985 300CD Cal myself.

MBeige · #9 12-02-2008, 09:13 PM

Pulsing? Doesn't that mean warped rotors?

Chad300tdt · #10 12-02-2008, 09:22 PM

The pulsing I'm referring to can be felt in the pedal, but can be heard under the dash right where the booster is. Maybe popping is a better description ... like ABS feels when it's being activated.

EDIT: I should also mention, that when I overhauled the brake system, I had to extract brake fluid out of the booster from a leaky MC. I cleaned it up the best I could, but I figured I'd need to be replacing it at some point.

I believe that the bellow/baffle inside the booster is beginning to finally let go where about 1 cup of brake fluid had been sitting before I drained it out of there.

Also, when the popping occurs, the pedal gets harder and when I let off it goes back to normal for the next push until it pops again.

Johnhef · #11 12-02-2008, 11:11 PM

damn man for $54 I would have done it. the booster in my SEC was bad when I got it.... that booster was something like $600 or so iirc. my parts car donated its booster to the cause

Cr from Texas · #12 12-03-2008, 01:01 AM

Quote:

Originally Posted by Chad300tdt

UPDATE:

my123ca, I did end up using 1st gen. 126 calipers and rotors for the fronts.

I also ended up buying a 1985 300CD Cal myself.

Chad, If you used the 126 calipers and rotors I assume you had to change to 15" wheels. What did you use? Please don't tell yet another member has beat me to an elusive set of 15" bundts.

Chad300tdt · #13 12-03-2008, 08:09 AM

Quote:

Originally Posted by Cr from Texas

Chad, If you used the 126 calipers and rotors I assume you had to change to 15" wheels. What did you use? Please don't tell yet another member has beat me to an elusive set of 15" bundts.

I used 1st Generation w126 calipers and rotors (up to 1985). They fit under the 14" bundts as the only difference from w123 calipers and rotors is that the w126 rotors are thicker due to being vented and the calipers just have a shorter piston to allow for that.

If you use 2nd Generation w126 brakes, the rotors and calipers are actually larger and won't fit under the 14" bundt.

So, don't worry, I haven't found 15" bundts.

Chad300tdt · #14 12-03-2008, 10:42 PM

DONE!!

That upper left nut on the booster bracket under the dash was tricky indeed.

Thankfully I have many extensions including a flex extension that worked well for that one. I used a little piece of shop rag to hold the nuts in the socket to get them started on the studs.

No more popping.

3play · #15 12-04-2008, 10:48 PM

Hi Guys. I'm new to this list and having a brake problem. I have replaced the master cylinder in the 85 TD 3 times and it still won't pump up. I have bled the lines until they run clean, but it still wont hold pressure. It will pump up, but then you can push it to the floor. Could the reservoir be sucking air at the seals? Would a bad booster do this? (I can't see how it would) I really can't figure this one out.. BTW, there are no leaks to be seen anywhere. Also, where did you get the inexpensive booster??? The ones I have sen were over $200 Thanks for any help! MM