Commencing Rear Brake Replacement - PeachParts Mercedes-Benz Forum

rmmagow · #1 10-04-2012, 01:05 PM

1985 300D, faulty rear brakes.
Planning to replace calipers, rotors and flex lines.
Only scared of the flex lines. Any tips to removing the flex line from the metal brake line? Penetrant like PB? Should I try to get the clip off and the flex line out of the mount first? I know to use a brake type wrench on the metal line fitting but is there something else I should be wrenching as a counter hold to trying to get the fitting off the flex line? I have about 1/2 day to get this done and am essentially terrified I will screw something up and need to change a bunch of hard lines. I don't know for 100% if the flex lines are bad, I don't get a squirt from the frozen caliper when undoing the bleeder but am thinking that at 192,000 miles the flex line aught to be changed out anyway.
Done brakes many times, flex lines on other cars (and had a lot of grief) and I just want this to go as smooth and quickly as possible as I need the car to be running ASAP. Other than the brakes, the old girl is running great with new glow plugs and a valve adjustment.

toomany MBZ · #2 10-04-2012, 01:12 PM

Use a penetrant, but no teflon tape.

Stretch · #3 10-04-2012, 01:23 PM

Essentially the best thing to do is to tackle the flexible brake pipe at the top and not at the caliper. If you undo the caliper end first you'll find that there is not enough "swivel" for it to come out.

If I remember correctly you need a 11mm open ended spanner to undo the joint between flexible pipe and hard brake line - you undo the part on the hard brake line and hold the flexible pipe fast. You might find that people have already visited them with mole grips...

...if so an unbent hard line is still available at the dealer (well it was the last time I checked)...

...you can of course make up your own lines if needed but then you need to double flare them - and then we end up in one of those is it legal not to double flare them conversations (which seems to be different in different parts of the world).

rmmagow · #4 10-04-2012, 02:50 PM

Quote:

Originally Posted by Army

Essentially the best thing to do is to tackle the flexible brake pipe at the top and not at the caliper. If you undo the caliper end first you'll find that there is not enough "swivel" for it to come out.

If I remember correctly you need a 11mm open ended spanner to undo the joint between flexible pipe and hard brake line - you undo the part on the hard brake line and hold the flexible pipe fast. You might find that people have already visited them with mole grips...

...if so an unbent hard line is still available at the dealer (well it was the last time I checked)...

...you can of course make up your own lines if needed but then you need to double flare them - and then we end up in one of those is it legal not to double flare them conversations (which seems to be different in different parts of the world).

Thanks Army. I've had the whole caliper off, the flex line at the caliper won't be a problem. I'm going to have a close look at what I have on the other end of the flex line. It doesn't look chewed up and may even come off easily. I'd probably have to make up my own line. Hate it but I do have a double flare maker. I used some kind of softer brake line to fix my old Mazda. It double flared pretty nicely and no leaks right off the bat. With this old beast I screwed myself by not driving it for almost three months, the brakes had been fine before then. Caliper rebuild didn't go well, piston was too damaged so now a re-built set is going in, both sides.

Diesel911 · #5 10-04-2012, 03:12 PM

Quote:

Originally Posted by rmmagow

Thanks Army. I've had the whole caliper off, the flex line at the caliper won't be a problem. I'm going to have a close look at what I have on the other end of the flex line. It doesn't look chewed up and may even come off easily. I'd probably have to make up my own line. Hate it but I do have a double flare maker. I used some kind of softer brake line to fix my old Mazda. It double flared pretty nicely and no leaks right off the bat. With this old beast I screwed myself by not driving it for almost three months, the brakes had been fine before then. Caliper rebuild didn't go well, piston was too damaged so now a re-built set is going in, both sides.

The hard Brake Lines use a "Bubble" type Flare; not the double flare that is on the lines of American Cars.
You can buy a Bubble Flare Kit for that; I got mine on eBay so I don't know if they are common at the Auto Part Chain stores or not.

People say this is the brake tubing that is easy to bend without kinking;
Brake Tubing Cunifer™ .

I think you can also by Genereic Bubble Flare tubing with the Fittings on them in verious stock lengths; but, I have never looked for any.

charmalu · #6 10-04-2012, 10:02 PM

Here is Cinifer`s webb site.

Federal Hill Trading Co.

Charlie

Codifex Maximus · #7 10-05-2012, 03:59 AM

I wouldn't replace the metal lines unless they obviously leak or are damaged. I am very glad I didn't have to replace mine. Would've been good experience though...

Use brake line wrenches of high quality so you don't damage your lines. I've just had to do this very job and had this exact same issue as you're having; good wrenches definitely help.

P.S. Check your parking brake shoes while yer in there.

Stretch · #8 10-05-2012, 08:08 AM

Quote:

Originally Posted by Diesel911

The hard Brake Lines use a "Bubble" type Flare; not the double flare that is on the lines of American Cars.
You can buy a Bubble Flare Kit for that; I got mine on eBay so I don't know if they are common at the Auto Part Chain stores or not.

People say this is the brake tubing that is easy to bend without kinking;
Brake Tubing Cunifer™ .

I think you can also by Genereic Bubble Flare tubing with the Fittings on them in verious stock lengths; but, I have never looked for any.

Really? So it is double bubble trouble then...

Chad300tdt · #9 10-05-2012, 08:16 AM

Quote:

Originally Posted by rmmagow

1985 300D, faulty rear brakes.
Planning to replace calipers, rotors and flex lines.
Only scared of the flex lines. Any tips to removing the flex line from the metal brake line? Penetrant like PB? Should I try to get the clip off and the flex line out of the mount first? I know to use a brake type wrench on the metal line fitting but is there something else I should be wrenching as a counter hold to trying to get the fitting off the flex line? I have about 1/2 day to get this done and am essentially terrified I will screw something up and need to change a bunch of hard lines. I don't know for 100% if the flex lines are bad, I don't get a squirt from the frozen caliper when undoing the bleeder but am thinking that at 192,000 miles the flex line aught to be changed out anyway.
Done brakes many times, flex lines on other cars (and had a lot of grief) and I just want this to go as smooth and quickly as possible as I need the car to be running ASAP. Other than the brakes, the old girl is running great with new glow plugs and a valve adjustment.

When I remove any flare nut I get the wrenches in place and try to align them so I can squeeze them together like the handles of a pliers. You can do it to tighten or loosen. If that doesn't work I hold the wrenches with one hand at the nut and strike the wrench a few times until the nut comes loose. In my experience, when I tried to loosen a difficult flare nut, even after using penetrating oil, the flats on the nut start to round off. The impact has worked for me even on really beat looking flare nuts.

cullennewsom · #10 10-05-2012, 08:18 AM

Quote:

Any tips to removing the flex line from the metal brake line?

Use proper flare-nut wrenches.

Yes, here in the US you can buy pre-cut metal brake line with nuts and ends flared, or you can buy a flaring tool, as someone mentioned before, get the correct double-flare tool.

cullennewsom · #11 10-05-2012, 08:20 AM

Quote:

Originally Posted by Chad300tdt

When I remove any flare nut I get the wrenches in place and try to align them so I can squeeze them together like the handles of a pliers. You can do it to tighten or loosen. If that doesn't work I hold the wrenches with one hand at the nut and strike the wrench a few times until the nut comes loose. In my experience, when I tried to loosen a difficult flare nut, even after using penetrating oil, the flats on the nut start to round off. The impact has worked for me even on really beat looking flare nuts.

Seconded.

rmmagow · #12 10-06-2012, 05:13 PM

And Done!
Took about 5 hours. If I were 25 yo, maybe could have been done in 2.5 but I'm much closer to 65 than 25.
For the flex lines, 11mm on the brake line side, 14mm backup on the flex line itself and pull. They came off easily with no rounding. Rebuilt calipers, new Beck Arnley rotors (they are actually Zimmerman from Germany). Calipers came loaded so this job was wildly straight forward. Power bleed with a Motive pressure bleeder. Brake pedal with car not running is hard as a rock and does not slowly move downward. Car running the pedal feels pretty low but I'm thinking the new brakes need to settle in. Cer is starting it's 600 miles a week chores next week until it snows. I pull it off the road at first salt.
Thanks for all the advice.

Diesel911 · #13 10-06-2012, 09:04 PM

Quote:

Originally Posted by Army

Really? So it is double bubble trouble then...

I have a double flare kit also and have used that a bunch of times on the job since 1975.
Double flaring new tubing is not too much of a problem if you measure the end correctly but tubing that has been on the Vehicle a while seems to work harden and is not as flexiable.

The cheaper Flaring sets somtimes do not grip the Tube well and the other tools in the kit have a sloppy fit.

Some kits have something so you measure how much should stick out and some don't.
It is easy not to start off with enough Tubing to begin with and then if the Tubing slips down in the clamp you even have less.

I don't know if bubble flaring is easier or not as I have not had to do it yet.

In the pic the Double Flare is on the Left and the Bubble Flare is on the right.

rmmagow · #14 10-23-2012, 09:26 AM

1000 miles into the brake job and all seems well. The low brake pedal seems like it might be slowly coming up a tiny bit as the pads set and the inside piston rubbers let the piston come out more. The fronts looked pretty much OK and will last until spring. For a non-ABS brake system, this thing can haul down pretty quick and smooth with a heavy brake. Nice old W123, I'm keeping this one for life (or until I can find a nice Boxster to play with :-).

Chad300tdt · #15 10-23-2012, 09:47 AM

When I bleed brakes I usually use a Motive Pressure Bleeder.

I've always had an unsatisfactory pedal feel afterward on w123s, so I prefer to put the car on 4 stands and have a helper pump the pedal (using a block to limit travel) while the car is running. This method has always given a proper bleed and a good firm pedal. I believe the w123s need to be bled while using the booster and vacuum.