gjuckett

While highway driving, I stepped on the brakes and the peddle went to the floor. I continued to pump the brakes and finally a little bit of the brake peddle engaged (very spongy and close to the floor) and the car pulled to the left (only the left caliper grabbed) and I had to quickly fight with the steering to get to the brake down lane. Within a couple of seconds before I could get into the brakedown lane, the brake peddle went to the floor again. I continued to pump repeatedly and could not get the brakes to engage. I had to coast to a stop using neutral. Yes I was prepared to use the emergency brakes but did'nt.

Upon unscrewing the master cylinder cover, I found I had brake fluid right up to the top. No wheel cylinders or lines or hoses had malfunctioned. Since DOT requires dual reservoir master cylinders, how come the master cylinder failed and one side of the master cylinder did not show a loss of brake fluid.

Does anyone have any idea as to what happened with this brake system failure.

Thanks, Gary

backlash1

Hi Gary
The fact that you recovered at least some pedal after pumping your brakes suggests that you might have had air in the system and not a master cylinder failure. This could be due to the system drawing air through an opening in your hoses, connectors or seals. It could also happen if your fluid was too old (it absorbs water, which will boil at high temp releasing water vapour) or if the fluid overheats due to a sticky brake caliper. I've seen master cylinders fail but never all channels at once. cheers
marc

dac122

Wow, scary situation. That'll cost you a pair of soiled shorts. But seriously, glad to hear you stopped safely!

Check for any stuck calipers or wheel cylinders. Check passenger right and driver rear diagonal first, since the left was partly working. Then I'd drain, flush, refill and bleed the entire system. Check with others on this forum on how to flush the entire system without air locking anything.

I'm leaning toward brake fluid boiling as well.

Please share your outcome, as a safety issue like this will benefit many on this forum.

gjuckett

Howdy All,

Although there was no loss of break fluid, no cracks in the break hoses to the calipers, no stuck wheel cylinders, this lead me to believe the master cylinder had failed somehow. My research on this issue identified that the break system design now has two break fluid reservoirs designed into the system (required for all cars in the US) that would prevent the loss of the breaking system if a component was to fail. So I had the master cylinder replaced and as of this date the breaks are fine. No spongeness, low peddle, or pulling to one side. Thanks for your replies Backlash1 and dac122. It was greatly appreciated.
Gary
ford taurus break failure with no loss of break fluid found.

dac122

Thanks for the follow-up.

You are correct, all cars sold in the US since the 60's or 70's (not sure exactly when) have all been dual piston/reservoir required with diagonal braking runs. I believe this design originated from a European model (Volvo, Mercedes, Saab?). One diagonal is connected to the primary (forward) piston, the other diagonal to secondary piston. In the event of piston/reservoir/diagonal failure, you still have partial front and rear brakes on the other subsystem helping to brake straighter.

I've never experienced a master cylinder (partial) failure, but it sounds scary.

jwko

I had the exact same problem with my 01. My wife came home one day and said the brake peddle went to the floor and she had to pump it to get brakes. I went out and drove it and everything was fine & told her she was crazy. Long story short, few day's later I was driving it and went to slow for a curve and no brakes and was like OH S***! I repaced the master cylinder and no problems since.

gjuckett

Howdy JWKO,

Your picture in your reply reminds me of the 1970 GTO judge 400ci (sleeper) I had bought for $1800 in 1972. About a month or so later, as I started my Goat, it sounded like there was a chain rattling in the engine. Low and behold, someone previously had left the old pushrods in the oil pan, under the valley, and a push rod made it up into the crankshaft. $1200 bucks later, many pizzas, working only on friday afternoons, while working for a new and used car dealor, we pulled the motor, sent the block out for bore and stroke, .30 over, .15 off the heads, heads ground and ported, siameze pistons, new street cam and lifter package, new crank, new clutch, rebuilt 4bbl carter carb, new pressure plate and throughout bearing, we, the three mechanics and I, jump into the monster and take it up on the hghy and the crazy mechanic floors it and says, it's do or die. As we break 130, I'm screeming the front tires are bald. The Goat speedometer went past 140 and held against the center post of the guage at 6 oclock. When we pulled back to 60, I thought I could run as fast as we were going. I had to sell the beast a short time later. $40 a week on gas at .28 per gallon, a set of tires every two weeks rotating fronts to backs, couldn't afford to keep in pace with the G60s, and the additional cost of rebuilding, when my insurance came up for $1250 for the next 12 months, to be paid in full since I was only 18, I didn't have the money. Couldn't sell the car outright cause everyone thought gas was going to go up to $3 a gallon. Eventually sold it for $1100 to a local pontiac dealor. And this car was premo condition. I wouldn't let anyone sit in it with their shoes on. Waxed twice a week, buffed with dupont number 7 every other week, damped toweled twice a day, changed the pin striping every other day, bathed the interior every sunday including dying the rugs, washed and waxed the engine compartment every saturday including paint touch-up, remember I mentioned I worked for dealor. I eventually left the auto world years later. After many other auto challenges. I'm bald...he-he.
Gary

jwko

I bet you wish you still had that car

That pic is from Two Lane Blacktop, I highly recommend it, it's a gooden' It's been long out of print and pretty much only available as a bootleg on ebay. A few years back I bought a whole auction lot of Two Lane Blacktop movies on ebay and all were copys, that taught me not to buy without a pic but anyway. I still have a few copys laying around I would share if anyone wants to see it.