sudden total brake failure
 

Two weeks ago I finally got the '71 220D I tried to buy a year ago and drove it 400 miles to visit family. When I got to my exit I immediately headed 1/2 block to Starbuck's and while in line, holding my brakes, the pedal suddenly went TO THE FLOOR. My "new" car now had no brakes, no brake pedal - it went all the way to the floor with little effort, and no brakes at all. I managed to get to a safe place to park it and call for a ride. WHAT HAPPENED? Anyone have an idea? The brakes pulled to the right, a strong pull, when I'd braked while driving that day. There had been a slight pull when I'd driven short distances around town before I left and on the trip it seemed worse. Please, help me figure out what might be wrong so I can fix it and get home! I am a DIY-er, as I've more determination than cash, so help is very much appreciated.

Check for any brake fluid leakage under the car. Then check the fluid level in the master cylinder. If it's low, fill it up and pump the brakes until you can find the leak. If the master cylinder is full, and you're satisfied there's no leakage, the problem is likely a bad master cylinder that blew an internal seal. Post back with what you find.

Thank you for such a quick response!! I did notice the fluid in the brake reservoir was there but the front seemed to have slightly LESS fluid than the back one did. Another factor I forgot to mention is a noise from the car that I can't really describe except it was short in duration and sounded like something broke OR "POPPED". When nothing immediately happened I forgot it... old cars that sit in sheds for five+ years are expected to grunt and groan.... Do these two pieces of my puzzle help?

sounds like a brake line has blown right out, considering it was so sudden; old lines rust from the inside out. brake fluid actually actracts condensation, especially in an old car sitting in storage.

Today I will get back to the car and look for brake fluid where it shouldn't be. Would a blown brake line or a master cyclinder leave brake fluid in the master cylinder? If a brake line goes, in the front, would braking be almost nothing? Is there a schematic I can find somewhere that'll show me where the lines run? Brake line replacement... if this is it should I replace ALL the brake lines? and master cylinder... of course OE, but, new as opposed to rebuilt or junkyard? So many questions... so little time. Thanks guys!!

replace all lines and master cylinder. only way to ensure peace of mind.

Brake parts (calipers, brake lines, and master cylinder) aren't really good junk-yard parts. It's better to go with rebuilt or new parts.

You need to go on a hunt to find where it's leaking. Like I mentioned before, try pumping the brakes a lot while topping off the master cylinder with fluid. Some leaks need a high volume of flow before they become apparent under the car.

If the problem is a corroded brake line, it may be a good idea to replace all the lines, depending on how bad the rest of the lines look. It's a judgement call....it depends on how you feel about your car, how long you plan to drive it, and what level of "tune" you want to keep it in, etc.

Did you say this car sat for five years in a shed unused?....that's tough on any car. Cars need to be exercised, or they'll stop working. First thing to suffer from storage is the braking system. You may want to do a COMPLETE brake job - rebuild all calipers, flush the brake fluid - once you identify your immediate problem.

Okay! Checked out the car and ground underneath and found brake fluid leaking from a line running from above to the wheel's center (+/-). It's leak is obvious and the front part of the master cylinder's fluid level is considerable lower than it was when I parked the car. There was also a leak, of oil I suppose, coming from the center of the engine area, apparently completely separate from the master cylinder/left-side area (although it's approximately even with brake fluid puddle in relation to the front and back of car).

Since I'm operating in emergency mode I would like to replace all that was suggested earlier later when I get home, and, just fix what must be fixed until then, I gather I can get just this one line replaced? Or....

What do ya'll think? Can I wrap "emergency-repair tape" around it or should I get it replaced?

As always, answerers are appreciated!!!

Don't even think about the tape. Pressure on sudden stop could blow it in a heartbeat (perhaps your last). Replace.

afraid duct tape can't fix everything
 

I didn't think so, but had to ask anyway.

Replace it I will. What is the line made of? Is it hard to DIY? Expensive? and don't forget labor co$t$ if a garage does it?

The brake line is a tube called "Bundy" tubing specially manufactured for automotive brake line application, which can see pressures up to 3000 psi. It's not expensive and widely available in any auto supply house.

If you can't get the exact length of tubing, you should consider investing in a tube cutter and tube flaring kit to make your custom lengths. It should cost around $30. Bending the tube can be trick...if you don't do it right you can kink the tube and render it useless. They sell tube bending tools (not expensive), but if you're resourceful you can do a decent job without these tools.

Unless I misunderstand the system, the diagnosis is missing something. If you have a dual master cylinder, even if a brake line fails you should have brakes on two wheels since the brake line systems on front and back should be independent of each other. If you have no brakes at all, there is a problem with both front and back wheels somwhere. Perhaps the comment about the master cylinder is correct and that is the additional problem.
Let me venture a guess. If the car had been pulling to one side all along, the brake line had been leaking all along with only one wheel having brakes in that part of the system causing the pulling. When the pedal went to the floor, something in the master cylinder failed causing the other set of wheels to lose their brakes. You can rebuild the master cylinder.

High pressure hoses with no cheap taped repairs, gotcha!! Looking at the line it was obviously blown out under high pressure and that blowout was the popping sound I heard. Pressurized hoses are very serious work and when I get home (IF I ever do) I'll get all these lines replaced. Hopefully, this one can be replaced and I can MAKE it home safely.

Kerry edwards pointed out that I should've had SOME braking left after losing one. The brakes pull was strong to the left on the trip down and the front left blew out.

This is a wonderful forum with the MOST HELPFUL FOLKS all over the world.

If it was pulling to the left, this is an indication that the left brake was working better than the right brake. If you have a complete failure of one front brake while the other is working the pull will be quite violent at anything over crawling speeds.
Chances are, your back brakes were not working and when the line failed you lost the remaining two front brakes.
A complete brake rebuild seems to be in order.

debbiemarlow,

It seems you may have had one circuit not functioning when you picked the car up and the other failed when you were driving it. If this is the case, fixing the one line you are aware of that blew when you were driving will at best restore the condition you experienced when you picked the car up.

The braking system is set up to give you one circuit for the two front brakes and one rear with the other doing the two front brakes and the other rear. Blowing out the front brake line hose disables both "circuits" as they really only back up the master cylinder and only one hose connects the hydraulic system to each brake. The master cylinder has dynamic seals, meaning things that seal when the piston moves inside, and these things wear out over time, more so than the steel tubing or hoses, which see pressure cycles but very little wear and tear. The brake hoses and steel lines are therefore not usually considered high risk for failure items and the cost of having check valves and the like in the calipers to allow multiple lines to each brake would probably lead to more reliability problems than less. And definitely more cost.

When you found the leak, did you first fill the master cylinder reservoir all the way up? The reservoir is designed to fill the rear compartment by overflowing the front one. The partition is there in case the line going to the single rear brake, or the clutch which is fed from the rear compartment, develops a leak and the fluid is all drained out. You still have the front compartment and the brakes it services left. The front can also drain if the line to the other rear brake is lost without taking the whole brake system out.

So, it would seem you have a leaking clutch hydraulic element, or a bad rear brake caliper or hose/steel line that is causing your second circuit to be inoperable. This could explain the pulling you experienced if it was not too violent. Since rear brakes, even when they are new, don't do too much of the braking duty with car going forward, it is unlikely really violent pulling (that wants to wrench the wheel out of your hands) is coming from the scenario I described with one rear brake not working due to a hydraulic leak.

I would also suspect both rear brakes are basically non-functional if the car has been sitting idle for years, and that you have a poorly performing front right brake caliper, also from being idle for years. The black stuff you see all around the brakes and wheels from burning off the pad liner is full of carbon, which is galvanically active when wet and in contact with steel, so it causes corrosion that can bind things up pretty good if it is left to corrode for years. Daily use prevents most of this from being serious, except on those rear brakes. Even with daily use it is probable that the rear brakes will eventually stick due to corrosion since they are so inactive compared to the front ones.

This got a little long, but your issue is a safety issue. You are much better off with an automobile that won't go than a car that can't stop. While brakes will cost you a few hundred dollars to completely rebuild/replace, it is the only way to go. Hope this helps, Jim

This might be your problem...
 

I had that happen to me awhile back on my 380 sl. Turns out the vaccum assist had blown out (big circular black thing that fits between the master cylinder and the firewall). I had virtually no brakes but it would stop if I pushed all the way to the floor.

There is a hose with a check valve that could be leaking or the cylinder itself.

Turn the car on, pump the brakes, if your pedal comes back up a bit your vacuum is working. If when you apply the brake, it slowly goes back down, you have a leak in the vaccum assist.

3 different brake places I went to missed it so you might as well check it out.

J. Boggs

Guess what?
 

It HAD some kind of tape already on the brake line and it was covered by electrical tape! I have NO idea who or why... but, I didn't do it. Perhaps some other person feels like duct tape can solve most any problem, too!

My mechanical friend called and reported I need two front brake lines which he'll put on this week. He's very good and hopefully this will solve my brake problem until I get home. Then I'll see about a thorough replacement of old brake lines. Should I replace or have the master cylinder rebuilt? Or leave it alone until it goes bad?

I have learned more than I ever imagined there was to know about my brake system. Thanks to all who helped me here!! But, don't go away because if this fixes my brakes, I know, it won't be long before something else "brakes". :)

Brake problem
 

Debbie,

When you eventually repair your brakes, make certain that the brake fluid that you put in the repaired system is the correct one recommended for your year Mercedes.

My 123 has a hydralic clutch that did exactly the same thing as your brakes did one year after replacing the clutch master cylinder. That's when I found that I'd used the wrong brake fluid which dissolved the seals in the system.

Good luck.

Ben

Oh, good tip on the correct brake fluid... dot 4, right?... I'll check with the garage and see what type they used.

Here's an up to date:
They replaced the two front brake lines and still no brakes. They replaced the master cylinder and now there's a very hard pedal. I haven't driven it yet, but they said it is VERY HARD to stop the car pressing pedal VERY HARD. It's getting expensive. Last phone call and they were thinking the vacuum line.

Note: I found out this afternoon that the master cylinder was replaced not long before the car ended up parked (due to minor traffic accident). Does anyone think it could have really have gone bad? And a bad master cylinder is (1.) the whole thing or (2.) an O-ring seal or (3.) what? (I'm out of guesses). I'm uneasy about this $230++ replacement - should I ask for the "old" one back?

And the former owner's son says it was parked for three years, not five.

I've gotten really good information and am reluctant to ask... but... Besides the vacuum booster going bad, what else could cause a HARD PEDAL such as I described? I had no trouble shutting off the car when I cut it off several times and didn't notice any accessory malfunctioning.

As always, all advice appreciated!

Debbie :confused:

More questions:
Looking through the forums I have seen various prices such as:

Vacuum boosters:
One posting said "less than $50" another said "new booster is $240 and more from MB"

Master cylinders:
One posting said "$60" while mine cost approximately $230.

Am I shopping in the wrong places?

If the hard pedal means very little movement then then the calipers are crudded up, and not letting the pads move. The pressure you develop has to go somewhere, and that's why the line blew, and probably the "new" master cylinder. Replace the front calipers (click FastLane at the top of the screen, then Catalog at the left) and see if you have enough for emergency braking to get home. If your helpers didn't bench bleed the master cylinder then make them take it out and do it right. You're going to have to do the rear calipers and rear brake lines ASAP, so at this point you might as well buy all four rotors and pads for all four brakes and get the pain over with. Dollars to donuts the previous owner didn't bleed the brakes every year, and his neglect is now your problem and expense.

You can get home without vacuum (power) assist on the brakes. Just pretend it's the old days when nobody had power brakes.

Bad Brakes
 

Debbie,

Trust me, trust me, the problem with your brakes is in the mastercylinder. There may be nothing wrong with the master cylinder itself, just there's at least one air bubble trapped in there that causes the brakes to have lots of pedal but very little braking . I just solved this probelm myself, thanks to my son who suggested cracking the individual brake lines at the master cylinder and bleeding each one in turn right at the cylinder to get the air out. If your mechanics have a pressure bleeding device they might acheive the same thing.

Bleed, bleed, the master cylinder. Don't buy anything new until you're certain that they did that. If necessary stand right there and make them do it while you watch, they're going to be very embarassed when a female sovles their problem.

Put your foot on the pedal, press hard and long, if the pedal eventually goes all the way to the floor, it's air in the master cylinder.

When they eventually do it your way and bleed the master cylinder make this test again, if you now have brakes but the pedal eventually goes to the floor, bleed it again.


Ben

I'll check to see if the master cylinder was bench bled and what he thought about the caliphers. I've got the car back and the brake is hard and braking is harder and the car doesn't stop easily but I can manage:D I hope:eek: !!

When I get home all of your ideas will be passed along to my neighboring mechanic and I'll ask him to "help me" (means: fix it for me) get replacements to rear caliphers and front, if needed, rotors... think I oughta bite the bullet and do rotors, too?... rear brake lines checked to see if they are clogged. Anything else?

Sam, the mechanic here in Germantown (where I am visiting), checked the vacuum and said it was good. I remember a post discussing a broken check valve... but, he would've detected that right off, huh? Sam is a trusted friend of my family here and I know I and my little 220D have been in the best hands. I spoke with him about many of the ideas presented here and he patiently listened but he already knew (much more than I).

I've ANOTHER PROBLEM! The car's huge Interstate battery will not start the car, even after being jumped off and driven for 1/2 hour. I turned it off and tried... dead. Here's what I think has happened: Before I left, the car's alternator light was slightly aglow (and I knew the former owner's soldering job that he was unsure about and said "have it resoldered by someone who can reach it") so I checked the wires he showed me. Sure enough, they were apart and when I touched them together the alternator light went out. So another helper friend and I took the wire, stripped it slightly more, and attached it to a bolt. No more light, no more problem....
In the Chilton manual for '68-'73 MBs, on page 84, it says:
4. If the molded connector is disconnected from the alternator, do not ground the hot wire. There MIGHT have been some sort of molded metal connector on the wire that we stripped. I can't remember... but, could we have grounded the hot wire? I think we attached it to the alternator and not the engine block. The alternator was recently rebuilt by an expert mechanic and reinstalled by the former owner.

Oh, yeah. The car started when jumped off with another battery.

Debbie

I am going to talk to Sam this evening. Please help me some more!!

Troubles
 

Debbie,

Sure sounds like your brake problem will be solved by your local mechanic if he bleeds the mastercylinder where the brake lines are screwed into it. You must have introduced some air into it when your brake line burst. By the way, where are you located in Tennessee, I'm from Nashville.

Ben

"There's only one"
 

East of Knoxville there's a community called Strawberry Plains, that's where I currently live. It got it's name from the pioneer days when horses hooves were colored red from all the wild strawberries there. Of course, it's in the Tennessee Valley and it's not a plain but after crossing the Smoky Mountains it must have seemed like one!!

And I love the Nashville and highland rim area. It's beautiful and as a collector of fossils and Indian and prehistoric relics, it is fabulous!!

Debbie,

Sounds like you bought the jimmy-rig special.

Yes, bite the bullet and do all the brakes when you get home. It's only your life (and other lives) at stake.

Sounds like the alternator regulator was jimmy-rigged. If your on-the-road mechanic is willing, then have him test the alternator after replacing the regulator. If he/you can't find a regulator then you can get home without the alternator. The car needs electricity for the brake and turn signal lights. If they work then pull the belt off the alternator, jump the car for an hour (STOP if the battery gets hot - it's shot and may explode) and get home so you can relax and fix the stuff right. Worst case is new regulator, new alternator brushes and/or alternator, and new battery.

I'm signing off as I just realized I'm not in Diesel Discussion. This part of the web site is for the 'real' mechanics, not us backyard yahoos.

What do you mean "jump the car for an hour"? You mean attach jumper cables from my battery to another and let the other car RUN for an hour? to build up my battery?

I'm almost afraid to start out.

debbie

I'm going to head out this Sunday a.m. for home. I appreciate the enormous generousity so many forum members have poured out in excellent advice and "maybe-check-this" pointers on my 220D's brake "blow-out".

I didn't understand the alternator/battery information but, I believe, if I get the car jumped off then, if I don't turn it off, it will "diesel-on" home. I think I'm going to love diesels -- it may not be this exact car though unfortunately.

Again, thanks everyone for sharing... and if you think about it Sunday, please pray that I'll have a safe trip home.

Sincerely, Debbie

:)

Going home
 

Debbie,

Let us know when you make it home. Good Dieseling!!

Ben

I'm home
 

MB roadside assistance jump started me. Details about trip home on the "Desperately Seeking...." thread. I "dieseled" on home, safely.

Thank you all for your help, concern, prayers.

MB'ers ARE AWESOME!!

Wouldn't it be nice if we had such a supportive system in all areas of our lives?!

db

if your brake pedal is still hard make sure they replaced the rubber seal between the booster and the master cylinder, without that seal the booster will NEVER get vacuum.
R

Sam checked vacuum and reported it to be good. But... the brakes are still have a hard pedal and the car's stopping power, well, I do have brakes now but they stop slower and that last bit of rolling takes an extra hard push on the pedal.

I'll have someone look at them.

db

Strawberry Plains girl
 

Debi,

You haven't mentioned whether your mechanic bled the brake lines at the master cylinder. If he doesn't do that, you'll have a great hard pedal but never enough brakes.

Have him try it, it only takes about two minutes with you pumping the brakes when he tells you to.

Ben