audible ping sound when release brake after full stop ??

[rhauptschein]

I am hearing an audible ping sound when I release the brake pedal after a full stop.
Any experiences on what this is, fix, etc?

[rhauptschein]

^ Maybe this is happening after an hour or more of driving and or after braking going down hill, low mountain.
I'm not able to reproduce when shorter, less strenuous driving.
Any experiences on what this is, fix, etc ?

[rhauptschein]

More details: I descended a steep drive way. And the ping returned upon releasing brake from full stop on level drive home (no ping when using brake to just slow down). After a few days of only surface level driving, no ping. But it will resume after a steep hill as described.

[pbierre]

Can you pin down which wheel is the pinger? When you're expecting the ping near the bottom of a hill, apply the handbrake concurrent with the brakes. If the ping is attenuated, that suggests it's one of the rear wheels. If it sounds unchanged, front wheel.

Then use sound reflection off of parked cars (passenger windows open) to decide if it's a passenger side or driver side.

Then, evaluate whether your rotors need replacing or just the brake pads, and have the parts ready to swap in. Recondition the brakes on the pinger wheel and its opposite.

If you could record and post a sound file of the "ping", you might get a better opinion.

I hate to guess, but sometimes you just swap in new parts, and fix it without root cause analysis.

[rhauptschein]

Can you pin down which wheel is the pinger? When you're expecting the ping near the bottom of a hill, apply the handbrake concurrent with the brakes. If the ping is attenuated, that suggests it's one of the rear wheels. If it sounds unchanged, front wheel.

Then use sound reflection off of parked cars (passenger windows open) to decide if it's a passenger side or driver side.

Then, evaluate whether your rotors need replacing or just the brake pads, and have the parts ready to swap in. Recondition the brakes on the pinger wheel and its opposite.

If you could record and post a sound file of the "ping", you might get a better opinion.

I hate to guess, but sometimes you just swap in new parts, and fix it without root cause analysis.

to clarify, the ping is heard when releasing the brake after a full stop - it can be on a flat surface; the decline described seems to be the initiating event

[rhauptschein]

Following up, seems problem was the Brake Booster.
The ping evolved more into the vacuum sounding hiss and occurred more frequently on level surfaces after a longer drive, when car heated up. Again when brake pedal released.
Not an inexpensive repair at the shop (parts, labor).
I wonder how potentially dangerous and if it would have evolved into losing power brakes which seems problematic with a heavy car.

[pbierre]

I got this from a website discussing the math of power brake systems. The force multiplication going from the brake pedal to the force of the front calipers pressing against the rotors is about 3500 lb / 70 lb. = 50X

There are 3 factors that stack up to make this 50X multiple:
1.5X Lever ratio of brake pedal
4X power steering booster
8X hydraulic ratio (area of caliper pistons / area of master cylinder piston)

These are approximate.

Now you can see the impact of losing the power brake booster function. You'll have to press 4X as hard on the pedal to get the same decelleration!
You won't be able to put 70 lb. X 4 (280 lb. of force) on the pedal, so you'll notice the drastic enlargement in stopping distances.

Cars are very heavy objects, and power-assisted brakes was a major stride in achieving safe driving speeds of 80 mph.