Sudden brake failure

Chuck

Supporter
This question has nothing to do with a GT40, rather it is a 1996 Nissan Maxima. But I need some insight on why there was a total brake failure.

A young driver was operating her 1996 Nissan Maxima around 45 mph when the vehicle in front stopped for traffic. She applied her brakes and the pedal went all the way to the floor - no brakes. She rear ended the vehicle than traveled down the road another 200 feet before finally bringing it to a stop with the hand brake.

The car has long since been scrapped and unfortunately no one looked at it to determine the cause.

The failure was sudden. No prior warning, no idiot lights, nothing out of the ordinary.

Presumably a Nissan of this vintage would have ABS and a dual circuit. Presumably a sudden rupture of one brake hose would not cause such a sudden and total failure thus I am wondering if it is more likely related to the brake pedal linkage or master cylinder.

Any ideas?
 
Late last year, a 1998 Neon. The wife was coming home from a trip to town. Got to our driveway and went to slow. The brake pedal went to the floor. Luckily, we live in a rural area. Luckily, she didn't have to slow for anyone in front of her. She used the parking brake to slow and pull into the next driveway.

Stepping on the brake pedal resulted in a puddle of brake fluid just in front of the left rear wheel. The brake line to the left rear wheel had rusted through. Examination of why the dual circuit didn't work showed the following. The left rear and right front wheels are on one circuit. Right rear and left front on the other. The reservoir on the master cylinder has no divider between the two circuits. The master cylinder sets on an angle so the circuit on the lowest part of the reservoir is the last to loose fluid.....which appeared to be the left rear and right front, the one that was leaking. Thus it worked while it worked, but once the fluid fell below the front part of the reservoir........no brakes.

I find it amazing that there are not some better standards on brake lines, fuel lines, brake rotors, etc. concerning corrosion. A rubber or vinyl coating on lines, more nickel in or galvanized coating on rotors. For the few dollars involved it sure would increase the safety and longevity of the vehicle. As for the design of the Neon's brake system, what were they thinking?? A 2 cent piece of plastic in the reservoir would have prevented "no brakes".

But then again, I got the Neon for nothing, literally. It belonged to a friend and had broken a timing belt (from a failed water pump bearing). It had bent valves. The owner didn't want to spend any $ on it and said "hey, you want a car? For nothing..come pick it up". So I did.
We've always been Honda people so a Neon is a bit of a departure. It isn't really that bad of a car but they sure didn't make it easy to work on.

All brake lines and fuel lines have been replaced.

Dave
 

Randy V

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Chuck - That vehicle has a dual braking system and even if you lost a hose you would have the other end of the car or at least diagonal braking depending on how the vehicle's brake pressure combination / proportioning valve is plumbed,

My thought is that she had a check valve in the power brake booster go bad (stuck open) which would give her absolutely no boost and the pedal in some cars goes rock hard almost as though it went all the way to the floor. I have also seen it where the pedal drops substantially without boost before going hard but still engaging the brakes.

If you want to prove the theory out, it would be simply done by disconnecting the vacuum hose from the booster and pressing the brake a few times to exhaust the residual pressure in the booster. This would be done in the same year/make/model car..

Hope that helps...
 
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For a total failure it is hydraulic.
Most likely the master cylinder.
If it looses the front circuit it won’t stop well on the rears and most people will say they had nothing bcause that is what it feels like.
If it has cross braking it may feel a little better but not much.

As the car is gone there is no evidence, if the master reservoir is full it is the master it has failed between the front and rear circuit as it is a tandem cylinder with a single bore.
If the booster had failed it would have a hard pedal.
If the res is low or empty it is corner related,brake hose,pipe bla bla bla.
If an ABS unit fails it will not have ABS but it will have brakes.
Nissans use a level senser, if it gets a leak the driver generaly gets a warning lamp.

The other one is road condition(lots of oil at traffic lights) some will claim no pedal but in reality it was ABSing.
Or she was SMS ing and forgot about everyone else on the road.
Most will use the brake failure excuse.

After the accident did the car have a pedal.

For all you guys with duel master cylinders, use the tilton short bore cyl.
When a master fails in a normal length master the balance bar kicks sidways and the pedal will run out of travel on the good cyl.
I did the test at 100kmph with the long m/cyl, front and rear curcuits were disabled consecutivly and it was not impresive.
On the short bore m/cyl it has a pedal.

Jim
 
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My Girlfriends 96 Volvo had a situation where the brake pedal would go almost to the floor, and ABS would engage on a clear dry day...very unnerving. We finally traced it to a small piece of rust from the rear parking brake which is a small set of shoes inside the rotor. A small chip of rust would get stuck on the abs sensor which looks like a small fork, this was telling the computer that that wheel was stopped.
I agree that brake lines are terribly inadequate as far as materials used. I regularly replace them with stainless and they are good for the life of the vehicle. The worst ones I have seen are the black coated ones used on some new vehicles, total junk.
Cheers
Phil
 
With a modern dual circuit braking system it would be unlikely for the problem to be downstream of the master cylinder. It's possible the car had been braking on only one circuit for some time...and then the second circuit let go with a leak too, but that would be a pretty rare occurrence.

Certainly, the MC could go bad but that's usually progressive rather than sudden. Was the gal having to pump the pedal and pressure up before this failure?

There's a chance the pedal attachment for the piston rod broke off, or the rod itself dropped out of the MC somehow - that has happened before.

Hard to know without a wreck to look at.
 
To be honest it sounds like the classic design fault with a lot of the front drive cars out there today.
Split diagonal is the problem. If you are not hard on the brakes and lets face it most of us aren't on the road. You can loose a circuit on the split diagonal and not notice it. It is not until that circuit fails and all of a sudden no brakes. (had it happen) Split pipe from mechanical damage, and finally found one set of seals in the master cylinder stuffed when we couldn't get the brakes working on all four. We ended up converting it to a front rear system as with testing on the track we were unhappy with the way the car behaved with a simulated failure. i.e. one diagonal set clamped off. Under normal road style braking the differance was almost nill. Jusy a slight increase in foot preasure to stop. Under severe braking, i.e. emergancy braking, we spun the car on several ocasions, it didn't mater what we did, the result was still the same. Unacceptable.
Split diagonal systems are used by manufacturers today as a cheap way of meeting the dual system performance requirements.
 

Chuck

Supporter
Thanks for the input. Good thoughts. The bottom line is it can happen and there are a couple of alternative explanations. I have not yet found any problems unique to this particular Nissan, so I would expect it was an age related failure (14 year old car at time)
 
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