Wow, thanks everyone, I’ll take note of when it happens.
I realize this is GQ, but there are about a dozen ways you could have phrased this to avoid coming off so pedantic and condescending.
after brakes are worked on they should be tested, both driving and parking brakes, before taking the car out on the road,
if you get the brakes serviced by someone then to test find out where their car is parked. with your car 30 yards away get to a street driving speed and apply brakes with distance enough to avoid a collision.
You can also get spongy brake pedals (pedal fade) due to overheated brakes boiling the brake fluid. If the sponginess occurs after a period of sustained or hard braking, and passes after a short period of time, this may be the cause. You need to get the brake fluid checked/replaced as it may have contaminants that boil sooner than expected (water, generally), and you may need to modify your driving technique to avoid overheating the brakes.
si, does that even happen (apart from spirited driving on a track)? How does water or anything else get into the fluid with there being a much greater problem?
Last time it happened to me it was when descending the Alps into Austria on a single carriageway road - steep grade, lots of turns - with an overheating engine so engine braking was limited.
Many brake fluids are hygroscopic, which means they absorb water from the air. This is why proper brake maintenance is so important.
(bolding mine)
IANACM (I am not a ‘certified’ mechanic)
Kind of a :nitpick:…
On some makes/models of vehicles the ‘emergency’ brake is not… well, an actual ‘emergency’ brake, as much as it is a ‘parking’ brake.
As an example, on the Chevrolet 1/2 ton Silverado P/U the mechanical foot brake pedal (next to the sidewall) is designated as a ‘parking’ brake. That model of P/U (equipped w/4 wheel disc bakes) utilizes a small ‘drum’ type brake in the rear wheels, along with the normal disc brake. The smaller drum brake is not sufficient enough to stop the vehicle in an emergency situation (in my experience).
Granted, it’s better than nothing, but I think that it’s primarily meant to be used as a ‘parking brake’.
For instance, when parking on an incline, the brake can be set to keep from relying on the transmission alone, to keep the vehicle from rolling.
Hopefully, Gary T will check back in and give his professional opinion on this.
I don’t know if any manufacturer calls it an emergency brake nowadays, though I gather the term was more common decades ago. I think the fear is that the term “emergency brake” suggests it’s a more or less an equivalent substitute for the service brake (the regular hydraulic brake system operated by the brake pedal), whereas it provides nowhere near as much stopping power. While it can be helpful – as you say, better than nothing – in some emergency situations, it’s designed to be effective at keeping a parked car from rolling. It is not very effective at stopping a moving vehicle, especially at higher speeds.
Si, I agree with you about proper brake maintenance.
I am curious about an overheating engine not being much use to slow down your rig in the alps. In the Colorado Rockies, I use engine braking with hot engines often. I have not experienced any problems from this practice. In fact it cools the engine fairly fast. It also saves your brakes from overheating.
As I am sure you are aware, there is an old truckers “rule” that one should descend a mountain in the same gear that was used to ascend the mountain. In other words, use engine braking to keep your speed down while descending. So why could you not have done that?
Respectfully yours, 48.
The overheating was due to a leaky gasket but I didn’t actually know that at the time - if the revs went up (as they do under engine braking) so did the heat, and I didn’t want to stress the engine any more than I had to, as we still had to get round Italy and home to the UK. I would have used the engine as a brake more in normal circumstances. I was just being cautious - I could get brakes replaced quickly - not a more serious engine problem.
Actually, it raises a point about modern car technology.
When I learned to drive in the 80’s (in 70’s era cars), we had to know about brake fade due to old brake fluid, wet brakes, air bubbles or overheating. We also knew about stuck chokes, water in the carb float, loose distributor caps, leaky ignition leads, dirty spark plugs and loose tappet noise - a whole plethora of minor technical/mechanical issues you might need to deal with on an occasional basis, or at least be aware of. A generation older than me knew about reversing up steep hills because reverse was a lower ratio than first, and first didn’t have syncromesh so you had to stop to change into it.
Modern cars are much less prone to issues like those, and (it seems to me) many people are less prepared to deal with them. To be fair, though, I’ve probably forgotten plenty of that stuff myself.
I concur on all of those points.
My first vehicle was a '74 Chevy with a 3 speed manual transmission with the shift lever on the steering column, no less!
(When was the last time you saw one of those?) 
I’ve experienced brake fade on my motorcycle (a late-model BMW). Even with the brake fluid recently bled (i.e. moisture-free), the fluid started boiling while descending a twisty mountain road in SE Kentucky. The road had straightish sections where you could build up decent speed, but they were connected by sharp turns and switchbacks that required scrubbing off a lot of that speed. Repeat for a few minutes, and pretty soon my front brake lever started getting spongy. We stopped for a 10-15 minute brake, and lever feel returned to normal.
about 12 years ago I completely boiled the front brake during track riding. Pulled the lever all the way back to the bar with zero resistance, and achieved zero braking force. Ran off into the grass, somehow managed to get it stopped with just the rear brake. Decided I was done for the day at that point. 
Quote 'elf
about 12 years ago I completely boiled the front brake during track riding. Pulled the lever all the way back to the bar with zero resistance, and achieved zero braking force. Ran off into the grass, somehow managed to get it stopped with just the rear brake. Decided I was done for the day at that point.
Wow! That must have been fun! [/sarcasm]
**What causes a car brake pedal to “sink”? **
It’s not a witch.
Oops… that’s probably a more-accurate way to phrase it. As **Tripolar **mentioned, I was referring to the brake “fluid”, so i just kept that terminology. Thanks for keeping me on my toes!
I agree with your noting the tone in posts and being aware of its importance, but in this case I believe a nice GQ convention is being used appropriately.
By using the “nitpick” header, the poster can quickly zap in a quick fact or correction that is either nitpicky to the discussion, and is thereby excused from introduction and reference beyond the mere posting of fact, or may be important enough in other discussions but not helpful to get into in the current one.
Nitpicking typos or grammatical errors, for an extreme example, is often seen and quite rewarding, bur bears the risk of complete nudnik-ity and eventual withering opprobrium, if not outright social exclusion.
But now we are in ATMB territory.
Best,
Leo
And on this side of the Pond reversing up a hill was because of gravity feed fuel system, Unless the fuel tank was full one would run out of fuel going forward. Then the gravity fuel tank was put up on the firewall instead of under the seat.
What do you mean creep?
Do you mean that when the handbrake applied, the car rolls when parked or creeps when it is running and in gear?
The latter tends to cause the former.
(Automatic) when in drive, the car would still move forward even with the handbrake applied.