Replace Master Cylinder Brakes Still Go To The Floor



Brake pedal has been going to the floor barely slowing the car. We replaced the slave and master cylinder, pressure bled the system, still wouldn't go into gear. If you replace yours with a rebuilt one use better judgement than I did and make sure you have one that works perfectly so it will last the 4-5 years that they are supposed to instead of the 1 year and 4 months mine did. same as before I replaced master cyl. A vehicle with a bad brake master cylinder will have inoperable or compromised brakes, and therefore will be unsafe to drive. Toyota 4Runner 1996-2002: How to Replace Brake Master Cylinder Has your brake pedal become spongy, or does your foot go all the way to the floor when you try to press it? It might be time to replace your brake master cylinder. Over time seals get worn in the master cylinder and can leak. Attach the brake line to the back side of the cylinder with a tubing wrench. Have a pretty good pedal now, though still not as firm as I'd like. On most cars, trucks, etc. hello, 2006 f150 5. I used a CarQuest 20-2234 (which corresponds to a GM 14009146). Soft brakes after installing a new master cylinder The pedal is a good bit softer than it was before the new master cylinder. This is a 77 Nova. The garage I go to has done the bleeding and they even replaced the master cylinder again but the problem is still there. Rather than holding the pressure generated by the master cylinder and using it to apply the brakes, the leak allows the pressure to dissipate and the fluid to leak out of the system. Have to floor brake pedal to stop the car. Unless you are a glutton for punishment, a brand spanking new one is the way to go. Cylinder on caliper is pushing out with no presser. Master Cylinder: Don't Ruin Your Master Cylinder While Bleeding. New master brake cylinder. All I got was super spongy brakes (all the way down), so after bleeding the heck out of all the wheels maybe 5 times without getting any brakes, I replaced the Master Cylinder. Sometimes when driving, the pedal movement will go from hard to very soft with a lot of travel. Brakes still go to floor. controls fluid flow to the rear brakes allowing the piston in the master cylinder to go past center and control pressure to all the brake assy's. Check the Brake Fluid Level: Anytime you have a brake pedal that goes to the floor raise the hood and locate the brake master cylinder's reservoir. Re: P-30 FRONT BRAKE LOCKING SOLVED! mike e: 7-24-06 : Walter may need more info, you say no brakes,does the pedal just go to the floor with no or little resistance. And oddly, I have tried everything you have in about the same order. The reason being is that I did the WJ knuckle swap & I now have bigger front brakes and my rear brakes are from a ford explorer so I need a brake system that can handle the large calipers & whatnots. I had to adjust the rear brakes because they weren't working right. While the brakes are up I >start the truck and my foot goes right to the floor and I can't pump up >the. I have some I have rebuilt and some I have replaced. A defective master cylinder and low brake fluid are common reasons why a brake pedal goes to the floor. The Brake booster is a vacuum-powered part in your car which helps the brakes to work by asserting pressure on them. If your brake pedal goes to the floor on your Ford F-150 or F-250 Super Duty, it might be a good idea to change your master cylinder. If you stomp on the brakes the truck stops like it normally should, but if you ease into it, it will keep right on rolling. I then bypassed the abs. I've seen too many master cylinders ruptured by having someone push on the brake pedal and allowing it to go all the way to the floor when bleeding. All I got was super spongy brakes (all the way down), so after bleeding the heck out of all the wheels maybe 5 times without getting any brakes, I replaced the Master Cylinder. like i said i'm not trying to be a smart ass as some people on the forums are but i took everything that was told to me in consideration, did some research and. bleed the brakes using the scanner. Changed the master cylinder today, old one had some bits of what appeared to be rubber gasket floating around inside of it so I'm assuming an internal leak. I could get the rear to lock up but just barely. Left it overnight with a piece of wood between seat and pedal holding clutch firmly to floor while contemplating best place to buy clutch from. I have changed brake pads and bled the brake fluid plenty of times, but never had soft brake pedal at the end. How to fix a brake pedal that sinks in your car DIY with Scotty Kilmer. i have installed all new pads and shoes, bled all the lines and the master cylinder. Normal brake pad and shoe wear causes the fluid level to drop in the master cylinder over time. Therefore, we bled the brakes again, still spongy. Attempts & Checks so far:. To bleed a master cylinder, start by lifting up the car with a jack so you can work underneath it. My cousin replaced the master cylinder and blead the four wheels and all was back to normal until yesterday about 2 weeks after the repalcement, back to the floor with the brake peddle. Why would the brake pedal go to the floor after the brake booster brakes and the brakes have bled still go to the floor? There is still air in the system. I was told it was the master cylinder. I can not find anything wrong with the master and there are no crimped lines. This article applies to the Honda Accord (1990-2002). How to Replace Master Cylinder Are your brakes acting funny? It might be time to replace the brake master cylinder. Over time seals get worn in the master cylinder and can leak. Then, I tried to bleed the rear brakes, as described above. A tech has just overhauled the front brakes on a vehicle with front disc and rear drum brakes. It has a proportioning valve mounted midway down the frame. Left it overnight with a piece of wood between seat and pedal holding clutch firmly to floor while contemplating best place to buy clutch from. The car owner had replaced rotors and pads on the front along with the master cylinder and still had a garbage pedal that would sink halfway to the floor before taking hold. Ford F150 F250: How to Replace the Brake Master Cylinder. This is NOT an exhaustive list of problems and is for guidance only. Ensure master cylinder is bench bled prior to installation. WHAT MASTER CYLINDER TO USE FOR DISK BRAKES BY EMERY STORA. Lastly we replace the rusted front to rear brake line so we won't have a puddle of brake fluid on the floor the first time we slam on the brakes!. Replied by jcc007 on topic Replaced rear brake shoes, now brakes spongy?!?! So If I adjust the star adjuster, then that would solve my brake pedal going all the way to the floor?? Also When I left up on the emergency brake it still goes into reverse and my brake light is now on in the truck. If you know your truck's brake fluid needs to be replaced, continue reading for this comprehensive guide for you to do the job yourself. With the engine off push the pedal as normal holding a slight pressure on it, If the pedal slowly goes to the floor replace the master cylinder. what you need to do is bleed your brakes (all 4 corners) starting at the whell ferthest from the master cylinder. Camaro and Firebird: How to Replace Brake Master Cylinder. The brake pedal will go to the floor and subsequent efforts to get a satisfactory brake pedal will fail. Jeep Grand Cherokee 1999-2004: How to Replace Brake Master Cylinder. 2001 Ford Ranger. If it goes down farther than normal and is hard to stop, then it's the brake booster. Brake pedal goes straight to floor with ignition on, stiff when off. Comments: Since still problem solved, I ordered Power Bleading system from Pelican Parts and going to replace Master cylinder and Blake pipes as well as Blake Flude for just in case. If your master cylinder doesn't work properly, or only works sometimes, you're going to lose braking power, and occasionally your brake pedal will go all the way to the floor. It does not go to the floor, just keeps moving until almost at the floor, then it stops and the brakes hold. Brake pedal goes almost all the way to the floor when applying the brakes. He replaced the master cylinder, adjusted the brakes and fixed a leaky line. About 2 months ago the Pedal Went to the floor. i had the brake booster, master cylinder, new brake pads and brake hydraulic system replaced 5 months ago and now it's doing the same thing again. I repeated the bleeding but still the same. This is done in a diagonally split hydraulic system. mirror, flashlight, etc. Shop by Category. When you fixed the brakes, did you take the lid off the master cylinder. The brakes were easy to apply (not much force), but the peddle would go all the way to the floor and would not lock up. I'm assuming that your's is original equipment as is mine on my 85. While the actual swap process is easy, there is one more step in the middle that you absolutely must do before you take the new unit to the car. Here's an additional reason a brake pedal could go all the way to the floor: a bad brake booster. Chevrolet Silverado 2007-2013: How to Replace Master Cylinder. Brake pedal has been going to the floor barely slowing the car. In the process I broke the caliper guide pins on one set, so I replaced those and carried on with the bleed. I replaced the master cylinder my self and I am still experiencing the same issue. this is the second time the brakes have failed in traffic. Clogged ports cause big problems. Replacing the master cylinder for your brakes or clutch is a fairly simple task – unbolt the old one, bolt the new one in place, swap the lines and you are done, right? Not exactly. Put in new master cylinder, no change. If the level is full or close to full that would probably be a symptom fluid leaking past the seals in your master cylinder. This means the total cost to replace the brake master cylinder will be anywhere from $323 to $498. The brake pedal goes nearly to the floor and barely stops the car. Brake pedal firm when engine not running. Brake hoses and pipes are what connect the brakes to the brake master cylinder, which has brake fluid in it. Brake pedal has been going to the floor barely slowing the car. Each thing I did made it a little better, but the pedal goes all the way to the floor every time I brake hard, and the truck doesn't stop very quickly at all. When the brake pedal is depressed, a push rod activates the master cylinder and pushes brake fluid to all four brakes at each corner of the vehicle. On some GM vehicles the master cylinder. Once I turn on the engine on, the brake pedal goes to the floor slowly. Pressure on the brake fluid cases the brakes to be applied to the wheels. I replaced the master cylinder my self and I am still experiencing the same issue. few things going on here: Installed just the front pads two days ago. Now what? Reply. SOLVED: I replaced my brake master cylinder and did a brake fluid flush. Bleeding your brakes will remove the air and replace it with new fluid. You simply refill it, and if the lines still have fluid in them, you can just stroke the pedal lightly to work the air out of the lines next to the ports. If the pedal is hard to push then maybe booster. Brake pedal going to the floor. if with constant pressure, the pedal goes to the floor, the master cylinder is bad. Take the car into a mechanic if there's reason to suspect the brake master cylinder is leaking. Here's the odd thing. This is what makes this tool a one person job when it comes to bleeding and flushing brakes. How to replace brake master cylinder in your car. Don't worry if you break them, your new master cylinder has them. I've been in a car when this has happened (but it happened suddenly), and yeah, it's scary as all get out. This is only necessary for brake fluid replacement of course, so you do not push 1 quart of old fluid into the system. Start the engine and the pedal goes to the floor and brakes are poor. Ford F150 F250: How to Replace the Brake Master Cylinder. In this tech article we will show you how to replace the brake master cylinder in a few easy steps. Bleeding the master cylinder on the car is possible, albeit slightly more time consuming, so bench bleeding is recommended to help get the process started. Booster can't be bad cause if I pump up my brakes while the car is off, and then hold the pedal down while I turn on the car the pedal goes down easy. [Editor] Master cylinders can develop a corroded bore outside the area swept by the seals. Toyota Tacoma: How to Replace Brake Master Cylinder A bad master cylinder in the Toyota Tacoma can make your brake pedal feel spongy, as well as affect your brake performance. I had a problem on my 1988 Ford E-350. Without brake booster, brakes cannot work properly, and if you are not taking care of the bad brake booster, it will cause dangerous accident. I question the master cylinder, brake booster, and ABS brake system (only because I'm not familiar with it). Because if you weren't filling the master cylinder as you were bleeding the brakes then their is a chance that you have a tone of air in the master cylinder and that would make the pedal go to the floor if this is the case than go out and buy some more brake fluid because you have allot more bleeding to do. Because most master cylinders are pretty airtight, you shouldn't lose brake fluid in any quantity unless it's leaking out somewhere else. Dirt can prevent the dump valve from fully seating and allow rear brake pressure to leak past the valve. Sometimes when driving, the pedal movement will go from hard to very soft with a lot of travel. I bled all four wheels using the pumping by an assitant method but the pedal would still go to the floor when pressed. It was original at 260k. In the dual-circuit system, one circuit operates the front brakes and the other operates the rear brakes. So then I thought maybe it's the master cylinder, so I got a new one and had it replaced, still break pedal goes all the way to the floor. Unless you are a glutton for punishment, a brand spanking new one is the way to go. This article applies to the Chevrolet Camaro. Left it overnight with a piece of wood between seat and pedal holding clutch firmly to floor while contemplating best place to buy clutch from. Next I pushed on the brake pedal, didn't sink at all and was very firm. Pedal falls to the floor. When the brake pedal is depressed, a push rod activates the master cylinder and pushes brake fluid to all four brakes at each corner of the vehicle. but the pedal still sinks slowly to the floor. Master Cylinder Bad: A bad master. If there isn't enough brake fluid in the master cylinder to resist the piston, the pedal will go to the floor and the brakes won't function. Press the brake pedal firmly and run the Scan Tool Automated Bleed Procedure. Jeep Grand Cherokee 1993-2004: How to Bleed Brakes. Over time seals get worn in the master cylinder and can leak. Brake pedal goes almost to floor. Check the fuse. if with constant pressure, the pedal goes to the floor, the master cylinder is bad. When Do You Need to Replace Your Brakes? By Rick is low on fluid because of a leak or a problem with the brake master cylinder. This means the power booster is working properly, according to James E. If your brake fluid becomes tainted, the rubber seals on the master cylinder have broken and the fluid cannot effectively hold pressure. Replaced the master cylinder bled brakes, good pedal when not running but goes to floor when started - Bleeding brakes on a 95 Silverado after I replace. Who needs the extra work? If you goof and have to bleed the master cylinder, it’s the same deal as bleeding your brakes (friend and all). So, we have covered two problems that are likely to cause your brakes to sink to the floor: 1) A Brake Master Cylinder Failure. How To Bleed Toyota Abs Brakes. When the master cylinder goes, you may start to notice signs such as a brake pedal that feels mushy, spongy or unresponsive. Bleeding your brakes will remove the air and replace it with new fluid. He replaced the master cylinder, adjusted the brakes and fixed a leaky line. I have a Ford Focus 1. R+R both front calipers. Check the cylinder fluid. An empty cylinder will allow additional air to be drawn into the system. hello, 2006 f150 5. As title says, front left caliper was Siezed. Pedal falls to the floor. i added brake fluid on the road which was quite difficult i. Over time seals get worn in the master cylinder and can leak. A couple of ways to check. That would mean that you have a bad master cylinder. This feature applies the rear brakes first, which is a good thing on rainy or icy roads. But the biggest expense of the replacement job will be in the labor costs, which are around $230 to $300. No change, brakes still go to the floor, they still work, but they start working in the last 10% or so of pressing the pedal. Another common clue that the master cylinder is bad or going bad is a leak or wet spot on. Re: First hand experience with changing to the NBS master cylinder WOW! I did this today! Had uneven front pad wear due to a bad front, left caliper and was the perfect chance to do this while I was at it. sometimes when you stomp on the pedal hard the brakes will grab hard and then the pedal moves under your. Backed up and parked it by the shop and took the master cylinder cover off an it was close to bone dry with plenty of rusty looking schmegma in it. bleed the brakes using the scanner. In other words, the brakes. How to Replace Brake Master Cylinder If your brake pedal is squishy and you don't think your truck stops like it should, read on to learn how to replace an important component, the brake master cylinder. Chevrolet Silverado 2007-2013: How to Replace Master Cylinder. I just wonder if you spilled out your brake fluid. In part one in this series, we explain how to test for a low brake pedal by blocking the brake lines. watching for leaks , there were NO leaks. I recommend replacing it if you can. If no pressure builds up when pumping maybe wheel cylinder or caliper. the master cylinder is leaking. It's time to start suspecting something has gone wrong in. pedal goes all the way to the floor with no resistance. This is NOT an exhaustive list of problems and is for guidance only. And oddly, I have tried everything you have in about the same order. At this point I decided to replace the master cylinder. This was generally considered the reservoir for the drum brakes due to the sheer volume of fluid needed to push the brake shoes out followed by the return of all that fluid back to the master cylinder. I went to bleed the brakes, but I was getting no pressure at all and noticed a loud hissing noise when I pressed the pedal to the floor. Brake pedal goes almost all the way to the floor when applying the brakes. Quick Tips. could a cadillac man get a few suggestions?. it just goes all the way to the floor with only slight pressure near the floor ,, I can barely brake at all!! so i bought a new master cylinder and replaced it. We unthread the brake line from the rear T, underneath the car at the rear. Step 2 - Replace the master cylinder. I looked near the master cylinder and saw a brake fluid. My fluid color was a dark orange (rust from calipers over the years). A good indication of this condition is lack of fluid flow from the brake bleeders. I bled the brakes too. I question the master cylinder, brake booster, and ABS brake system (only because I'm not familiar with it). Brake pedal has been going to the floor barely slowing the car. The pedal only goes to the floor if there is no back pressure in the lines between the master cylinder the lines to the brake pistion on the calipers. bleed the brakes using the scanner. Master Cylinder and Boosters. I replaced master cylinder on 2013 ford edge but brake petal still goes to floor i have bleed the brake system so does that mean the brake booster needs to be replace Mechanic's Assistant: Have you tried cleaning and oiling the brake pedal's pivot under the dash?. if with constant pressure, the pedal goes to the floor, the master cylinder is bad. Show Full Signature 92 EX Sedan auto (RBM) - sold after 12 years (140k miles) 03 EX V6 Sedan auto (NBP, then Ford Blue) - traded in after 13 years (135k miles) 16 EX I4 CVT. but the pedal still sinks slowly to the floor. This article applies. Remember, the master cylinder is really a dual cylinder; the RR and LF brakes are operated by one and the LR and RF the other. A bad master cylinder is not something you want to wait to replace, because even with the redundancies, it can still cause loss of braking. Trust me, this setup will stop your truck very effectively! 32. If you do not have a diagnostic scanner you can try bleeding the brakes with the engine running to get the ABS pump to help bleed the air through it. A failure of a brake hose or steel line can be dangerous because it results in a loss of brake pressure in that brake circuit. Although rare, sometimes the master cylinder pushrod in the brake booster needs to be adjusted to either increase (not enough braking) or decrease (brakes dragging) braking application. While the brake pedal is down, detach the hoses from the brakes to the master cylinder and let the brake fluid drain into a container. Brake hoses and pipes are what connect the brakes to the brake master cylinder, which has brake fluid in it. Start the engine and the pedal goes to the floor and brakes are poor. Read also: 10 Signs Your Car Needs an Oil Change and Tune-up. When I replaced the MC, I did not bleed the ABS system - a buddy told me it was not necessary because bleeding at the wheels should take care of the entire line, ABS included. Emptied the reservior three times and still sucking air. To bleed a master cylinder, start by lifting up the car with a jack so you can work underneath it. If not, clean it up for reuse. controls fluid flow to the rear brakes allowing the piston in the master cylinder to go past center and control pressure to all the brake assy's. If a hose lets go or a saboteur has sawed through one of the brake lines, the other half will still provide a means of decelerating the vehicle, albeit with a lower pedal and reduced stopping power. Why do my brakes pump up after bleeding and still go to the floor when i start the truck? Already replace master cylinder and booster, good fluid coming out of bleeders, ??????????? Posted by Kevin Simpson on Jul 23, 2014. It has good vacuum at 18″ and is steady. sometimes when you stomp on the pedal hard the brakes will grab hard and then the pedal moves under your. Doesn't feel like the common "air in the system" type of pedal fade. This feature applies the rear brakes first, which is a good thing on rainy or icy roads. The brake line was already disconnected from the brake master cylinder at the front. It does not go to the floor, just keeps moving until almost at the floor, then it stops and the brakes hold. Skip to Main Content. Head to the parts store, swap a reman in, bench bleed, gravity bleed, then full bleed normal sequence RR-LR-FR-FL, solid streams, pedal solid when off, fire the truck up, pedal goes straight to the floor. When dual reservoir master cylinders originally made it onto the scene, one of the reservoirs was much larger than the other. Repair center said master cyl. Always keeping the MC full of brake fluid. Master cylinders cannot be repaired and will need to be replaced. Virtually no fluid came out of the bleeder screws after many pumps of pedal. 4 …change the calipiers,brake hose, booster was leaking when pedal was pressed,new master cylinder was replaced twice thinking it was a bad master cylinder from auto zone. brought vehicle into shop and checked over, pedal is soft, if you pump it several times, it holds breifly and then fades away, the rear brakes were junk, there were chunks out of the rotors, replaced rear brakes, there are no lines leaking on vehicle, replaced the master cylinder. None of the lines going to any of the calipers are leaking. If your brake pedal goes to the floor on your Ford F-150 or F-250 Super Duty, it might be a good idea to change your master cylinder. Same effect and it was a pita to locate. Ok, part II of my winter projectI'm putting in a brake master cylinder from a 78 mercury marquis in my 95 YJ. Why would the brake pedal go to the floor after the brake booster brakes and the brakes have bled still go to the floor? There is still air in the system. The master cylinder works with your entire braking system. The following is a guide on how to replace a brake master cylinder. If not, clean it up for reuse. I can not find anything wrong with the master and there are no crimped lines. It did that for more than a year, new ATE fluid, new brakes, new left knuckle and still slowly to the floor. Why does brake pedal. This is NOT an exhaustive list of problems and is for guidance only. This mod will help your Jeep stop much better and it is a cheap, wonderful thing that you will appreciate every time you drive it. You look under the vehicle and there is a puddle beneath the truck. I went to bleed the brakes, but I was getting no pressure at all and noticed a loud hissing noise when I pressed the pedal to the floor. Open it one turn and the rears don’t work. At a stop light, I could not get my left foot under the pedal and if I pressed down even more it would go completely to the floor. New master brake cylinder. Bled the brakes. This is Classic Performance Products' new power brake kit that comes complete with everything you need to complete the conversion. The brake pedal going to the floor would indicate brake fluid leaking past the seals somewhere in the braking system. And, if these seals are not replaced timely, they may contaminate the brake fluid. - Edgar Blake. This article applies to the Mercedes-Benz E-Class and E-Class AMG (2002-2009). Luckily you roll on through with no cars in sight, but you are still left with no brakes. The pedal will then go to the floor. Replaced all four pads/rotors and performed a brake fluid flush, now my brake pedal isn't as firm as it should be, and it drops to the floor under constant pressure. few things going on here: Installed just the front pads two days ago. Part 1 of 2: Preparing the old master cylinder for removal. As the engine starts, you should feel the brake pedal moving down slightly towards the floor. To avoid this safety hazard, it is best to replace the brake master cylinder. He said the master was bad. what else can be wrong? I also noticed that the screw located in teh middle of the booster is being sucked in and not out or not pushing the fluid into the cylinder. Replaced a vacuum solenoid. I had a brake cylinder go out on my drivers side drum. 4 If both chambers of your master cylinder are filled with brake fluid to the proper level, close the master cylinder carefully, without letting any dirt fall into it. I have a 2003 Chevrolet Avalanche with a broken brake line. Hoping to get sine thoughts and some solution to this problem i am having. But the biggest expense of the replacement job will be in the labor costs, which are around $230 to $300. Now your helper, who is in the driver's seat, presses the brake pedal. But first of the brakes need to be adjusted. From experience (over 70 years of driving), I can say for sure that this will happen again and no amount of pumping will make the. Your problem really doesn't sound like air. bleed the brakes using the scanner. Brake paddle still soft. Take the car into a mechanic if there's reason to suspect the brake master cylinder is leaking. This article applies to the Honda Accord (1990-2002). That sorted the car will be perfect. customer has been driving vehicle with soft pedal for a couple of months, he has been pumping the brakes to stop. He said the master was bad. Any time that the brake pedal goes to the floor when the master cylinder is full of fluid, it is a failure of the piston and its seals in the master cylinder. The master cylinder is new-ish and the front calipers and pads are brand new and the rears have been overhauled. I started with replacing the master cylinder, with a known-good unit from my family's wrecking yard. Masters usually go out by losing pressure and going to the floor once but acting normal after a quick. Without brake booster, brakes cannot work properly, and if you are not taking care of the bad brake booster, it will cause dangerous accident. 4 If both chambers of your master cylinder are filled with brake fluid to the proper level, close the master cylinder carefully, without letting any dirt fall into it. Pedal still goes to the floor. When Do You Need to Replace Your Brakes? By Rick is low on fluid because of a leak or a problem with the brake master cylinder. if you repleaced a brake caliper on your truck and didnt pinch off the rubber line , then you have a but load of air in the system. The front and rear brakes of a dual-brake system have separate hydraulic circuits. If a hose lets go or a saboteur has sawed through one of the brake lines, the other half will still provide a means of decelerating the vehicle, albeit with a lower pedal and reduced stopping power. The master cylinder has only two output lines, likely to diagonally opposite wheel pairs (RF&LR, LF&RR) via the ABS module. Honda Accord: Why Does My Brake Pedal Go to the Floor? Why Does My Brake Pedal Go to the Floor? If your brakes go to the floor, a new master cylinder is in store. Just pull them out of the top of the master cylinder and watch the fluid run out. Why does brake pedal. Attach a new wheel cylinder to the backing plate with the original retaining nuts. Clogged ports cause big problems. Turns out, I was losing fluid out of the Master Cylinder. can it be the adjusting rod in the brake booster going to the master cylinder when brake pedal is pressed. It provides hydraulic fluid to the wheels. how difficult is this and how do you get started? it would seem nearly impossible to do everything through the little hole. Typically, if the braking master cylinder is losing its seals, it will need to be entirely replaced. Leaks lower the brake fluid reservoir, causing the pedal to constantly hit the floor when braking. The brake pedal sinks slowly to the floor at a red light. Like the nucleus of a cell, a Bronco master cylinder acts as a central hub for all things braking, which means that you must do your due diligence when it comes time to replace your unit. The brake pedal will go to the floor and subsequent efforts to get a satisfactory brake pedal will fail. Lastly we replace the rusted front to rear brake line so we won't have a puddle of brake fluid on the floor the first time we slam on the brakes!. As I would drive the car, it would slowly go lower and lower, until it would bottom out at the floor, but the car would still stop. If you bleed your brakes using the brake pedal, press the pedal only as far as it normally travels and no farther. You can buy a replacement master cylinder for your Buick LeSabre at PartsGeek. Sometimes when driving, the pedal movement will go from hard to very soft with a lot of travel. To avoid this safety hazard, it is best to replace the brake master cylinder. Another common clue that the master cylinder is bad or going bad is a leak or wet spot on. Suck the old fluid and sediment out of the master cylinder reservoir with a turkey baster or syringe. Usually what happens is the seals inside stop sealing, allowing fluid to pass and not build the pressure needed to expande the pistons in the calipers/wheel cylinders. Symptoms of a bad master cylinder include external and internal leaks. The kink allows pressure from the master cylinder through to the calipers, but won't allow it to release back to the master cylinder. No leaks, pads in good shape. OK, so I've replaced; the brake pads, rotors, fluid AND master cylinder, and it still goes to the floor. I replaced the booster and I still have the same thing. The reason I replaced master cylinder is that it was leaking fluid at junction with vacuum diaphragm. Ok so the shop said that it's the master cylinder. Could it be the ABS modual??? Brakes always worked fine, battery went dead and after replacing, the brakes acted up. I bought the car with questionable brakes. The Brake booster is a vacuum-powered part in your car which helps the brakes to work by asserting pressure on them.