Oh s**t No brakes!

[alpina]

Okay chaps, I need a little advise / help.  Today on trip out I had the brakes fail. Thankfully I managed
To pull over and stop safely. I must say this was quite a scary experience,  I was coming off a motorway
At the time, braking on the slip road, the brake pedal goes straight to floor. Some hard pressing slowed us
Enough to take the roundabout at the end of the slip road, luckily there were no other cars nearby.
Going round the roundabout I could hear a scraping from the left hand rear wheel.

Once stopped I could smell that unmistakable odour of brakes. I opened the bonnet / hood to
See that brake fluid had been sprayed around the engine bay,  Traces of brake fluid could be seen
Under the brake reservoir, over the master cylinder. It must of come out at some force as there were drips
On the underside of the hood. I managed to clean up the mess before any damage was done to any painted areas.
The brake reservoir is still full of fluid.

Recovery service got me home on a flat bed. So now I am waiting to get it booked in to get resolved.
Brakes are not something I want to be messing with.
So while I wait I would like to get you thoughts, and learn  what could have caused the loss of brake pedal ?
Last year new pads and disks/rotors were fitted. The Master cylinder and brake booster were replaced in 2016.

Thanks
DM.

[Cees Klumper]

Wow, that must have been very scary indeed. Did you manage to apply the handbrake at all?

Not an expert on brake systems and have never heard of something like this happening before, but what comes to my mind as you describe the issues, is perhaps a brake line or fitting ruptured somewhere in the system and applying the pedal forced brake fluid out of the break with some force, so that fluid went everywhere except to the brake calipers.

[Benz Dr.]

I had this happen to me a couple of times. The last time was right after a test drive ( car running while in the shop ) and the pedal went right to the floor. When we removed the leaking front caliper a chunk of the casting fell out right above the groove for the piston seal. The cracked piece was dull cast iron so it had been broken for quite a while. I've seen this happen before and while rare, it does happen. This could have been a very big accident.

Thing is, unless you pull the calipers off and take them all apart, there's not much chance of even seeing it. It's so deeply hidden, and because it's so rarely ever happens, why would you?  But maybe I'll start looking.........

[Pawel66]

What do you think could cause spraying of the brake fluid under the hood? I understand the rubber grommets between the reservoir and the master cylinder are not super tight and I know there is a vent in the cap, but what could cause such pressure build up there?

[stickandrudderman]

If fluid has been sprayed around the engine bay then it follows that it must have been under pressure which means it must be a ruptured brake line.

[alpina]

Hi Colin,  Thanks for your input. Would this also go with the brake noise I heard from the left hand rear
Brake ?  (a scraping noise that could only really be heard when going around a roundabout). This brake
Must have been rubbing,  once stopped it was the only one that smelled of burnt brakes. (yes, I sniffed all
The wheels!)
As I said brakes are not something I am going to tackle myself, but I am keen to learn from the incident.
While I have the car at home, is there anything I can look for ?  The brake reservoir is still full. The parking brake
Seems to work okay. The brake pedal now has a very long travel,  with some braking effect when the pedal
Is close to the floor.
Could the fluid have overheated / boiled and I now have air in the system ? 
How would I be able to discover a ruptured brake line ? until I you mentioned this I was thinking a failed brake hose
Causing the pressure build up resulting in the brake fluid being force out of the reservoir.  As they say a little knowledge is a dangerous thing.

[FGN59]

Something somewhat similar happened to me once: pedal to the floor as I pushed on it, no braking action whatsoever. Truly scary indeed. Luckily I was travelling slowly approaching a small village and there was no traffic so I was able to reduce speed gradually with engine braking and in the end with the handbrake, but I’d rather not live through something like that ever again.

It was the master cylinder which failed all of a sudden. (In fact a few hours later it was working again, at least superficially, but I couldn’t trust it and had it replaced). So altogether an easy diagnosis and simple repair (although this was on a Jaguar Mk2, where accessibility is an issue, as everything is shoehorned into a very tight space).

There is nothing mysterious or magical about brakes: it is like plumbing, every single element and connection must be inspected and tested for leaks, and if there are no leaks, it works (assuming the brake fluid is not contaminated with water). Good quality parts are essential for safety and security/reliability. As a self tought, and probably mediocre, mechanic, I have no qualms about fixing brakes. I reconditioned brake cylinders/callipers on my first ’oldie’, a 1968 Peugeot 204 roadster, changed the disks and the brake booster, and drove the car for nearly ten years without any braking issue. I work on the brakes on my tractor (no disks there, old fashioned heavy duty drums with mechanical action, no hydraulics).

The only tricky aspect is the part which regulates the pressure between front and rear wheels. If it doesn’t work as intended, keeping the car straight when braking hard, especially on a slippery surface, is sometimes difficult.

But as the experts among us underlined, there are some issues/frailties/breaks that do not reveal themselves obviously, unless you take everything apart or suffer an incident like alpinaltd or me. Having had your brakes worked on by an expert or having done the work yourself isn’t going to change anything to it. Let’s keep our collective fingers crossed that it doesn’t happen in a dire situation…

[alpina]

Well I could not resist to investigate what is going on. Looking under the rear of the car I notice one
Small drop of fluid. Looking directly above, I can see another drop on the left rear brake hose.
A picture of this is below.  Given that the left rear wheel was where the scraping noise was coming from
and smelled of burnt brakes. I removed the wheel to see what would be revealed. Well I sure looks like
was sticking on, and getting very hot. The disc / rotor was new 1000km ago and now looks quite scored,
whether this can be reused I would like your opinions. The inner most brake pad or what is left of it, is
loose and can be wobbled left and right. The outer pad does not move at all.
I can only guess that the fluid in the engine bay was forced out the tiny pin hole on the reservoir cap.
There is no other evidence, of leaking fluid any where else.
Let me know if you think the disc / rotor can be reused.
Thanks all.
DM

[ja17]

Sounds like your fluid boiled. If your fluid was old then the moisture in the system boiled and made your brakes go away. The heat build up could possibly be from the emergency brake being left on, a clogged brake hose, or a stuck caliper.