TOTAL brake failure?

[Dave G]

So yesterday I was cruising through shopping center land at 50 mph... Light ahead turned yellow so I hit the brakes & "thunk", the pedal went all the way to the floor with no resistance. Thankfully there was nobody in front of me and I went through the light right when it turned red. There was a nice wide sweeping entrance to a parking lot and I managed to swing in there and stop in a parking space with the hand brake.

Turned out that the steel line on the driver's side had burst in a major kinda way, and all the fluid leaked out within a few minutes of stopping. But WTF - I though the dual circuit brake system was supposed to leave me with half the brakes still functioning when something like this happens (?). Am I wrong about that?

91 Festiva, BTW...

[1990festiva]

Perhaps one circuit went out earlier and you didn't notice it until the other one went, might be a good place to start looking

[m715]

No, it is not your imagination Dave. When you lose a line like that, you have a precious two pumps of the pedal, then you are out. Look in the reservoir, and you will see slots that divert all the fluid to the wrong side.
The left front seems to be the first to blow right where it passes through th grommet. The next one, which may be ready to go on you right now, is the rear line at the front of the drivers side wheel opening where it makes a sharp 90 degree bend. The line, which passes over the fuel tank, to the right side brake hose, can be identified in that it has a coupler on it where it is made out of two lines, instead of one for what ever reason. If you see the same crusty corrosion as on the front line, FIX THIS NOW ALSO! It soon will fail after the front line. I have had this on three cars so far.

HTH
Michael

[Pu241]

I can confirm the left front failure right after the line passes the grommet.
drove home from the airport after midnight with only the handbrake.
Replaced both front lines.
Passenger side is easy.
Drivers side is a PITB, the line runs behind the filter mount assembly which after nearly 20 yrs doesn't come apart without a fight.

[Dave G]

Thanks all, but it sure seems like it ought to work better than this... I replaced the left rear a few months ago, and did both fronts this time. I did the press on it with all my might test several times and all seems to be OK. But it still seems like something ain't right.

[Pu241]

.....But it still seems like something ain't right.

What's it doing or not doing?

[Dave G]

What's it doing or not doing?

Well, it seem like I ought to have some braking when one side of the two circuit system fails! What's the point of the thing otherwise?

[m715]

Good question! I thought that was covered in the NTSA/FMVSS changes for all cars in 1966 1/2! How this slipped by, I have no idea!

Michael

[getnpsi]

Wow something to really check out when i buy my next project that's been sitting for 10 years.

[deathegg]

I think it may be some kind of design flaw, but only now are we discovering it since our cars are so old and are starting to have rusting brake lines?

Same thing happened to me in CA, TOTAL brake failure on the highway.

[WmWatt]

The brakes on my '89 continued to work with a leak in one line until the other side went so the combination valve on the firewall was doing it's job of partitioning the system. If both sides go at once the problem might lie ahead of the combination valve, eg. master cylinder?

[Mike McKown]

I think it may be some kind of design flaw, but only now are we discovering it since our cars are so old and are starting to have rusting brake lines?

Same thing happened to me in CA, TOTAL brake failure on the highway.

Common misconception that a dual master cylinder will still brake your car when a leak develops.

I've had it happen to me on three different vehicles. Total failure. Make that four now including one Festiva.

The master cylinder fails first in either the front or rear piston. The driver won't know it because the piston that is supposed to shift in the distribution block is stuck and won't make ground to turn on the brake warning light.

If you never make hard stops like me, you'll never know your master cylinder is bad until the system fails.

[deathegg]

Common misconception that a dual master cylinder will still brake your car when a leak develops.

I've had it happen to me on three different vehicles. Total failure. Make that four now including one Festiva.

The master cylinder fails first in either the front or rear piston. The driver won't know it because the piston that is supposed to shift in the distribution block is stuck and won't make ground to turn on the brake warning light.

If you never make hard stops like me, you'll never know your master cylinder is bad until the system fails.

But we're not talking about master cylinder failure; we're talking about a leak in a line. I was always taught and believed that if a line leaked (which supposedly serves 2 of the 4 wheels), the other line will be ok, and you'd still have 2-wheel braking. What am I not understanding?

To quote my '88 Festiva Service Manual: (italics and bolds are mine)
"The brake lines are arranged to form a split diagonal hydraulic system. Although the physical layout of the brake lines to not indicate it, they are arranged to form an "X". One side of the "X" supplies hydraulic pressure to the left front and right rear. The remaining circuit supplies pressure to the right front and left rear. The hydraulic system is split in this manner as a safety precaution. If hydraulic pressure is lost in one circuit, the remaining circuit can provide less efficient but balanced braking"

[Mike McKown]

But we're not talking about master cylinder failure; we're talking about a leak in a line. I

A failed master cylinder is exactly what we're talking about.

One chamber in it can fail and bypass and you will know nothing about it until the other chamber that has been doing most or all of the braking suddenly decides to take a dump.

If the distribution block has a stuck piston, it won't turn on the brake light until your brakes fail.

My brake shoes/pads last way over 100K miles on most vehicles so that should give you some kind of idea how hard I use my brakes normally.

[deathegg]

I see what you're saying, but I would think that people driving their cars would notice that they only have 1/2 brake power - or does everything seem fine on a daily basis and then FAIL? I guess that's what it is.

I've owned lots of cars, and I've had brake leaks before on other cars, and nothing like Total Failure has ever occurred, except on my Festy.