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