Brake / soft pedal trouble shooting, Brake pedal gone soft and fluid reservoir empty Options

[Fart/4]

Had the car for about 15 years
Never touched the brakes as in original ( to me )
Rotors , pads etc

Over the last about 100 miles brake pedal has gotten progressively
Softer and now go's down to the floor pretty much

Checked the reservoir and it's bone dry

Car still stops reasonable we'll , but pedal is very soft and is about 80% travel when brakes bite or engage

Should i immediately just take it to my aircooled guy/ mechanic

Or refill the fluid and see what happens approach
?


(IMG:style_emoticons/default/beer3.gif)

[GregAmy]

Had the car for about 15 years. Never touched the brakes as in original (to me) Rotors , pads etc

Might I suggest a refill and bleed? Or even better, new brake pads, then refill and bleed?

And are there any obvious leaks?

Reason I offer this, if you are still on your original brake pads, and there's no leaks, you may have simply run the brake fluid level too low due to normal wear of the pads. As pads wear, the pistons extend farther out and that lowers the reservoir fluid level. If you allow your pads to wear too much without regularly replenishing the fluid, you may have simply run it too low and started sucking in air*.

If this is the case, then a refill and bleed will resolve your brake pedal. However, this implies your pads are significantly worn out. Note that if you replace the pads after fill/bleed then you will overflow the reservoir as you are pushing back the pistons for the pads replacement...that's why I say replace pads first, refill the reservoir second, then bleed/flush the fluid last.

And if none of this mean anything to you then yeah, bring it to your guy to check out.

GA

*I don't have a hard date, but I think it it wasn't until sometime in the early- to mid-70s when the Federal Motor Vehicle Safety Standards (FMVSS) started requiring brake reservoirs large enough such that completely-worn-out pads/shoes all around would not result in air being introduced into the system.

And that does not take into consideration any leakage, introduction or water/contaminants, and/or evaporation.

S5.4.2 Reservoir capacity. Reservoirs, whether for master cylinders or other type systems, shall have a total minimum capacity equivalent to the fluid displacement resulting when all the wheel cylinders or caliper pistons serviced by the reservoirs move from a new lining, fully retracted position (as adjusted initially to the manufacturer's recommended setting) to a fully worn, fully applied position, as determined in accordance with S7.18 of this standard.

[fiacra]

Had the car for about 15 years. Never touched the brakes as in original (to me) Rotors , pads etc

Might I suggest a refill and bleed? Or even better, new brake pads, then refill and bleed?

And are there any obvious leaks?

Reason I offer this, if you are still on your original brake pads, and there's no leaks, you may have simply run the brake fluid level too low due to normal wear of the pads. As pads wear, the pistons extend farther out and that lowers the reservoir fluid level. If you allow your pads to wear too much without regularly replenishing the fluid, you may have simply run it too low and started sucking in air*.

If this is the case, then a refill and bleed will resolve your brake pedal. However, this implies your pads are significantly worn out. Note that if you replace the pads after fill/bleed then you will overflow the reservoir as you are pushing back the pistons for the pads replacement...that's why I say replace pads first, refill the reservoir second, then bleed/flush the fluid last.

And if none of this mean anything to you then yeah, bring it to your guy to check out.

GA

*I don't have a hard date, but I think it it wasn't until sometime in the early- to mid-70s when the Federal Motor Vehicle Safety Standards (FMVSS) started requiring brake reservoirs large enough such that completely-worn-out pads/shoes all around would not result in air being introduced into the system.

And that does not take into consideration any leakage, introduction or water/contaminants, and/or evaporation.

S5.4.2 Reservoir capacity. Reservoirs, whether for master cylinders or other type systems, shall have a total minimum capacity equivalent to the fluid displacement resulting when all the wheel cylinders or caliper pistons serviced by the reservoirs move from a new lining, fully retracted position (as adjusted initially to the manufacturer's recommended setting) to a fully worn, fully applied position, as determined in accordance with S7.18 of this standard.

Not bad advice IF your pedal is slowly going lower over a long period of time. However in this case the pedal got softer and lower over the period of time it took to drive 100 miles. Can't see pad wear as the culprit here. I'm going to take MC failure with leaking at the pedal cluster for $100 (IMG:style_emoticons/default/biggrin.gif)

[GregAmy]

Not bad advice IF your pedal is slowly going lower over a long period of time. However in this case the pedal got softer and lower over the period of time it took to drive 100 miles.

Though I am not discounting a potential master cylinder failure, all it takes is one burp of air sucked into the MC from an empty reservoir to cause an immediate, continuing, and dramatic loss of hydraulic pressure...you know, like when air is introduced into the system by a master cylinder failure.

Supporting that is the lack of notation of a visible leak, plus the "15 years" comment (how many miles/hours?) implying that regular inspection of the brake fluid level may not have occurred.

But yes, by all means, get it checked out. - GA

*"Ask me how I know"? Answer: from decades of bleeding race car brakes and being stoopit and not monitoring the reservoir level...one miscalc and the reservoir drops too low and then the pedal goes directly to the floor and you get to start aaaalllll over again...