Good brakes are just as important as a powerful engine. With the engine on the brakes felt rock hard. Poor pressure can result in more time, distance, and/or effort to stop. Refer to Hydraulic Brake System Bleeding. Low Sinking or Spongy Brake Pedal - Low Sinking or Spongy Brake Pedal Master cylinder may be leaking fluid pass the piston seals internally (by passing), not building up pressure. Continuing to push pedal down will eventually increase speed. But I'm getting a pedal that when pumped will stop, but otherwise is dropping to the floor board. The brakes need the engine to run to supply vacuum to the brake booster. Solution: This year Ka can suffer from water ingress to the PCM. There are no leaks anywhere on the car. after dong all l had to do with the straight transferre to new shell brakes were bled and everything,, engine off brake pedal like normal hrd but as soon as l strat the motor pedal goes straight to floor. Technician A says that a low, soft brake pedal is an indication of a defective booster. Fitting a larger bore master cylinder was mandatory to displace the volume of fluid required to operate the calipers but then with a single diaphragm booster pedal efforts became too high. Just got her back from bthe repair shop, and had been driving a rent a car(2015 Ford focus) and the difference between the braking is night/day. Then the pedal nearly goes to the floor. Re: Spongy Brakes After Caliper Replacement? 07/23/2010 3:38 AM If you can obtain a good solid pedal after bleeding the brakes without the engine running and the pedal holds the pressure and is up to the top of the pedal travel where it should be, to me that would signify the system is OK. After replacing the wheels I started the truck and pumped the brake pedal to set the calipers, the pressure never stabilized. A direct-acting servo is fitted between the brake pedal and the master cylinder. The pedal felt nice and hard with the engine off, started the engine and it was all soft and squishy. After the last session of the day prior, I notice brake fluid has left the overflow line, there's a puddle on the ground. But did you take of your cap to the brake reservoir, if not you may have turned the diaphame backwards inside your master cylinder. I have O2 Trailblazer the front brakes are dragging really hard in the brake pedal gets really hard to push I’ll pull the from the engine in a releases the air and it will release the brakes it doesn’t happen every time you drive it it takes time for the pressure to build up and then my brakes will drag real bad. I get a somewhat firm pedal until I start the engine. No Brakes!! Pedal goes to the floor and wont stop the vehicle. Waste gate solenoid. I have pumped up my brakes and bled them several times without the engine running, but when the engine is on the brake pedal has no feel to it. Its also worse when the engine is cold and just starts. Has anyone else had this problem. In almost all post 2000 German vehicles( mainly VWs -Mercs) while the engine is running and the vehicle is stationary if you push it hard the brake pedal will slowly go down to the floor. A soft or mushy brake pedal indicates that you may be low on brake fluid, or may need to bleed your brakes. This "spongy" pedal behavior applies =only= when the engine is running. Binding brake pedal mechanism. With the engine off, the pedal is hard. My daughter's 2004 GMC Envoy has had a soft brake pedal since we purchased it several years ago. Still stops good though. If your brake pedal feels spongy or goes to the floor, check your brake fluid immediately. now after only 6 months the brake pedal is soft. Losing control of the vehicle due to brake loss may cause injury to the operator or bystanders and vehicle damage. Apply and release brake pedal. Brake pedal is hard when vehicle is not running,but is soft when the 2005GMC Envoy is running. with the engine off you deplete all the vacuum reserve and the pedal becomes harder. If I plug the rear and just run the front, the pedal goes to the. My 2003 GS430 with 220k on it!!! developed a spongy brake pedal very similar to what you feel when your master cylinder goes out. If the pedal pumps up, is spongy but then holds a pedal and doesn’t leak down, then it has air in the outlets and needs bled. Father in law thinks it maybe booster. The brake pedal feels 'spongy' when you press it, and in severe cases the brakes will fail completely. a slowly sinking pedal is much more likely to be air in the system or contaminated fluid than a leak – both may give an initial firm pedal but compress more than standard brake fluid over time. T see the ABS - Answered by a verified Ford Mechanic. No hissing with this only. A replacement pedal with the same shape as the modified pedal would be made available at a later date. Do not fill master cylinder to top. The following is a list of the top ten warning signs that you are in need of brake service. I have noticed that after 45 min of driving and sitting at a redlight, it sems the brake pedal goes sorta soft, not to the floor, but noticeable. goes to floor when running! I have a nice firm brake pedal when the car is not running, as soon as I start the engine, the pedal goes almost to floor. But when I let off the brake pedal the red brake light on the dash turns off. On the last push of the brake pedal, hold moderate pressure on the brake pedal. Booster Test: With engine off, pump brake pedal to evacuate vacuum in booster. pedal is rock solid with out the truck running, start it up and the pedal is soft and has alot of travel the truck. Well today is the first snow we've had, first ive driven it in the snow. However, if the engine is running, it will fade to the floor if you continue to hold pressure on the pedal. If you put your foot on the brake and then start the engine the pedal should drop slightly and become a bit spongy, once the vacuum has built up. Still stops good though. Could be your pedal to master ratio, master rod length, excessive shoe or caliper travel, etc if it had air, I would expect the pedal to pump up as you repeatedly pump the pedal. 5) Engine has good vacuum and idle. With the engine running and the brake servo working and the increased force on the master cylinder a slight seal (internal) past the master cylinder seal would cause the pedal to sink. Start engine and keeping reservoir filled, run engine until fluid flowing from return hose runs clear. That's a pretty good indicator of air in the system. blew a rhs front diff to caliper rubber hose driving round last night replaced both front ones today with braided adr approved ones this arvo bleeded up brakes but are still spongy and were before the brake line blew and the pedal sinks to the floor slowly with the engine running and foot on pedal when stationary, was driving mates gq shorty round and his brakes are totally pretty much hard from the top of the stroke would my master cylinder be letting the rest of my system down by internal. Soft brakes after installing a new master cylinder I just put in a brand new master cylinder today and bled out all the lines. Does that mean the bleed is good? Brand new rotors, pads, new soft brake lines in front(for like a 2001 chevy since I put a 4" lift and the olds were short) and front wheel bearings. with the engine off you deplete all the vacuum reserve and the pedal becomes harder. If the car is off the brake pedal pressure is firm. Classic Industries offers a wide selection of 1955 Chevrolet Two-Ten Series parts, including 1955 Chevrolet Two-Ten Series interior parts and soft trim, 1955 Chevrolet Two-Ten Series exterior sheet metal, 1955 Chevrolet Two-Ten Series moldings, 1955 Chevrolet Two-Ten Series emblems, 1955 Chevrolet Two-Ten Series weatherstrip and unique accessories, to nearly every nut and bolt needed for. I cleaned up, ready to feel a nice responsive set of stoppers and when the engine Fired up and the brake assist kicked in I was left with a very spongy pedal 3/4 of the way down experience. Re-bled system this time with engine running and it made no improvement still spongy, turned engine off and pushed pedal down twice and the pedal is how I would want it to be all the time, firm gradually increasing in pressure needed!. Do yourself a good turn and bleed the short distances first, then the longer distances last. My 2010 SL rogue’s brakes seem to be extremely spongy/floaty. The van failed the MOT because the brake pedal when pressed puts on the brakes but then moves all the way down to the bottom of the travel. I know I shouldn't have thrown parts at it but hey, at least now I have a new set up up top. The brakes have not been right since I bought it this summer. Seems like I need to press the pedal down close to half way before a good response to take off. 1) No fluid leaks 2) Changed master cylinder, bled system several times. There should be only minimal travel in the pedal before the brakes are engaged, and it should not require significant effort to slow or stop your vehicle. Brake pedal goes to the floor when engine is running. (Editor’s note: This article on how to measure brake pedal ratio is meant for skilled readers who Read more More than 90 years ago, the National Automotive Parts Association ("NAPA") was created to meet America’s growing need for an effective auto parts distribution system. Waste gate solenoid. Can hear no vacuum leaks or engine changes. Two Tech are discussing vacuum brake boosters. goes to floor when running! I have a nice firm brake pedal when the car is not running, as soon as I start the engine, the pedal goes almost to floor. ? As the title states, I realized on all my other vehicles, the brake pedal applied when the engine is turned off, it pumps 1-2times and then it gets "rock hard" or to the point that i cant press it down any further. Doing this two or three times (depending on if I have enough room to reapply) will get the pedal higher and firmer every time. Bled entire system. Disconnect the vacuum hose to the booster, pump the pedal a few times to get rid of stored vacuum, and check if the brake pedal stays up when putting a good amount of effort into pressing the brakes down. I then set up the bleeder as normal, filled it with fresh brake fluid and bleed the brakes normally going around the truck two or three times. I have read many posts on these trucks and their soft pedal problems and now I have to add to the list. If you feel it and see it swell when applying the brakes,it would be the problem. 0 and now have a spongy brake pedal that drops almost to the floor. they feel a bit spongy sometimes too. After 2 master cly. Apply the brakes with a moderate force (about 20 lbs of force). It's had new discs+ pads. I have to leave it a second and then pump again and it'll brake. ) If your vehicle has power brakes and stopping seems to take excessive effort, you may need to have the power booster replaced. I just replaced the proportioning valve because the old one was leaking. That's why a soft, spongy-feeling brake pedal that doesn't resist pressure and goes straight to the floor is a common sign that something's gone wrong in your brake system. If you have a hard pedal with the rear port blocked off then you do have a problem with the rears. Up until this point the brakes feel great it’s just the last second or two before stopping that the brake pedal drops. Oh ya engine on soft pedal and firm when off but still travels slowly down. With the engine stopped, depress the brake pedal several times using normal pressure. If the pedal will not pump up or will not hold a pedal at all, the entire master is not good and needs replaced. If so the problem is not the master cylinder but quite possibly vacuum related. My issue was up in the frame rail on old brake line, but I've seen similar issues with fittings. 3/16 line all around with one 2lb residual valve on the front circuit and one for the rear. I'm aware that there is probably air in the system somewhere, but I've bled through a significant amount of fluid with no bubbles coming out. Technician B says that there should be at least two power-assisted brake applications after the engine stops running. I thought adjusting the rears had it fixed but started van and brake pedal to floor again. I don´t really know if yours is excessive or not. It would stop no problem, even performed a few emergency stops but the pedal travel was to excessive. The answer of this question is the same answer of the different steering of a 90's car and a 30's car. I've changed the brake pads and twice and the rotors once so far and there is less pedal travel with new pads installed, but at times the resistance of the pedal changes when I press it far enough. If the car is off the brake pedal pressure is firm. One way to help with the problem is to find some place safe and slippery (grass, ice, snow, gravel, etc. I STILL cannot get a good, steady pedal. soft brake pedal Ok after one of my brake lines rotted away I decided to replace them all with stainless lines. Guys, I need some help here. In a clear area, step sharply on the brake pedal. Some engine conversions, such as a 4. A "soft," or "spongy," brake pedal describes a situation when the brake pedal does not have that firmness. As for fuel consumption, the CFE gets 8. Take it to a good brake shop they can fix it but you must likely have to replace it should coast about 150 to 200 to replace it. and once the engine is turned on, the brake pedal again, is easy to press down. I had to push it almost to the floor before it would begin to stop. The booster mounts at the firewall inside the engine compartment and a booster rod connects to the upper end of the brake pedal inside the cab. i then bled all 4 corners and got a few air bubbles out the front left. If you pump the brakes a few times or hold them down a while after you've turned off the engine, you will "use up" that vacuum and the pedal will feel hard. My 2010 SL rogue's brakes seem to be extremely spongy/floaty. Do not floor the brakes. Re: Brake Pedal Firm When Engine Off, Spongy With Engine Running - Now No Fluid Appearing When Bleeding Post by Tim_R » Wed Oct 17, 2012 9:01 pm I'm good thanks fella, I'll try and do some measurements on the cross link between the bell cranks which is as it left the factory as far as I know. Brake pedal goes to the floor when engine is running. With engine running and pumping the brake multiple times it does stiffen up a tad but hold your foot firm and you can feel that stiffness fade away as the pedal creeps forward. If I pump the pedal with the engine off, it stays high and doesn't fade. I park in my garage and there is no indication of a leak. Brakes were fine and bled before bushing job, but I opened a line not knowing I didnt have to take a front caliper off so I re-bled everything. I have noticed on the last couple of weeks that my brakes feel soft. If you step on the brake pedal and all of a sudden it feels like you're doing leg presses at the gym with a new personal trainer, your brake pedal may be too firm. Problem: Engine fan running continuously, rough engine running, misfiring and / or difficulty to start. If not then you should bleeed the brakes to get the excess air out of the lines. it does brake gradually as i press the pedal and if i jump on the pedal the anchors are out and it brakes pretty well. Went to the store, there for 15 minutes, went to start car, pedal hard. Then I disconnected the vacuum line from the brake booster and plugged it. you can also just pinch the rubber brake line behind the wheel with a vise-grip to check the rear wheel cylinders. Overheating the brake fluid can also cause a soft pedal. A brake pedal that goes to the floor is a scary problem. The master can leak internally in that brake pressure from one piston leaks past it’s seals and into the reservoir. I don't know any other reason for spongy brake pedal, other than air in the lines. The pedal will feel weird under your foot, you will hear strange noises, etc. When the engines' off, it's solid. found a bleed valve on f/offside was seized. I had everything new, removed the RWAL abs crap, nw MC, new calipers, wheel cylinders, brake shoes and pads etc. Some research is turning up threads on Dodge forums suggesting that rear brakes being out of adjustment might cause just these symptoms. Re: Soft Brake Pedal – 02-11-2008, 05:47 PM Originally Posted by igbell Well as I got it through a VAG specialist I got it cheaper than Eurocar parts would do it for, also when I go to the Eurocar Parts web site it comes up with parts for a Audi A6 and not a passat. That's the servo doing its job. you can also just pinch the rubber brake line behind the wheel with a vise-grip to check the rear wheel cylinders. With the car stationary and the engine running - if the brake is firmly. This is a bit of concern, as I tow a 2000 lb trailer at times,. A bad check valve would only cause vacuum not to hold in the booster when the car is turned off (should have 2 to 3 pushes of the pedal worth of vacuum in the brake system when the car is turned off. I stopped to get gas the engine was still running and I had my foot on the brake pedal when the pedal sudenly went to the floor. I cant see any brake fluid leaking, the only thing i suspect is a wheel cylinder in the back, would that cause this problem?. If you have a low pedal and no leakage it’s can also the master. Master cylinder defective. Reconnect the vacuum booster hose and run the engine at fast idle for 10 seconds. If the pedal slowly sank to the floorboard, then you had a leaky MC. However, if the engine is running, it will fade to the floor if you continue to hold pressure on the pedal. And with the truck not running I have a great pedal, not spongy in the least. The vacuum is created by the engine when it is running. DO NOT ride the brake pedal while going downhill. When you're out of brake fluid, your brakes simply won't work. It’s kinda scary when stoping is quickly and it seems like I am pushing the brake pedal to the floor. When the engines' off, it's solid. 0 litre N/A engine. Tech B says that there should be at least to power-assisted brake applications after the engine stops running. The pedal is a good bit softer than it was before the new master cylinder. Do yourself a good turn and bleed the short distances first, then the longer distances last. Loose Front Wheel BearingsIf the wheel bearings are loose on disc brake systems, they will allow the rotor to. Ended up changing right front brake caliper due to broken bleeder valve. One of the more common causes for the brake pedal going to the floor is a loss of brake fluid. I changed the brake pads, rotors, and changed one caliper. Operation, Diagnosis and Repair of HYDRO-BOOST Power Assist Systems Bill Williams, Technical Contributor Hydro-boost power assist was introduced in 1973 by Bendix as an alternative to the vacuum booster. It may lead to other problems such as, brakes operating without braking, front brakes heating up or smelling after only a short time, lack of acceleration or the need to make hard use of the accelerator. If I pumped the brakes a few times while stopping (to build pressure) it felt normal. · Allow fresh outside air into the work area to clear the exhaust fumes out. The engine cut off can be from several reasons including a broken timing belt, bad fuel pump and loss of. Problem: Brake drag or brake pedal slow return. This can cause rotor wobble, and the caliper pistons will retract too far into the caliper, giving a spongy pedal when the brakes are hit. Really soft brake pedal and long throw. after dong all l had to do with the straight transferre to new shell brakes were bled and everything,, engine off brake pedal like normal hrd but as soon as l strat the motor pedal goes straight to floor. So new pads and discs (rotors) still the same. Pedal was hard as a rock. But when running the brake pedal goes to the floor. Spongy Pedal. i then bled all 4 corners and got a few air bubbles out the front left. Ordinarily this has no effect on the engine, but repeated and rapid presses and releases of the brake pedal will increase the volume of air that passes into the inlet manifold. I get a somewhat firm pedal until I start the engine. With engine running, brake pedal sinks down when depressed but no spongy feel or lack of performance. It's kinda scary when stoping is quickly and it seems like I am pushing the brake pedal to the floor. Every time I hit the pedal, it was too soft, the pump kick in and after a short pump run, I had brakes again. Step 2 the master cylinder where it attaches to brake pedal if sinking spongy brake pedal with abs system nothing works watch fixed step 2 Pics of : Brake Pedal Slowly Goes Floor Engine Running How To Fix A Brake Pedal Going The Floor In Under 45 Minutes -> Source : www. Less pressure will be needed to hold the pedal down. After further investigating it was a sized near side caliper, that sorted showed up a warped disc. I am running the 7/8" master cylinder and proportioning valve is wide open to the rears right now. With rear brakes plug off and front calipers working we loose the pedal with engine. From your question, I know that the car has power brakes. Pedal was hard as a rock. Q: I have a 1980 Oldsmobile Cutlass sedan with the 231 V6 engine. If the rears are adjusted properly then you problem is the wheel cylinders. If the pedal still has one or two assisted applications before getting hard to press, likely no leak exists. It definitely won't be as boosted as factory, but keep in mind, when you are cruising, the engine will make 20" or so, and the booster will "store" that level of vacuum for the first press. Well you have a softer pedal with the engine running because you have the vacuum assist helping you. Exterior; Auto Off Projector Beam Led Low/High Beam Daytime Running Auto-Leveling Headlamps; Black Grille; Black Power Side Mirrors w/Manual Folding; Black Side Windows Trim, Blac. When you're out of brake fluid, your brakes simply won't work. Step off the brakes, with the car's engine turned off. pedal is still soft with the engine running. I noticed from the history the brake fluid hadnt been changed since 2015 and the brakes felt quite spongy so this weekend just gone, I bled the system using my trusty Eezibleed. Rear brakes not working properly; Excessive rotor run-out causes the rotor to wobble as it turns. (e) Apply brake pedal. There is a simple way you can check its operation yourself. That's a pretty good indicator of air in the system. If you can get the brake pedal to creep with the engine switched off and servo exhausted, or actually under braking there is a serious problem that requires urgent attention! A road test maybe an option to satisfy yourself, but if in doubt give the benefit of the doubt to the vehicle presenter. Soft brake pedal (2002 Honda Civic) Hi,we have 2002 1. Pump the brake pedal several times with the engine off until the pedal requires more effort to depress. A8 / S8 (D2 Platform) Discussion - Soft brakes - Brake Acculumator / Bomb - Being annoying me for a long time, I just dont think the pedal feel should be this soft. Our view is, if the vehicle pulls up to roadworthy standards on a road test, the spongy, creeping pedal at idle is not a major issue. Don’t push like you are panic stopping, simply hold pressure like you are sitting at a red light. Presumably it is putting the brakes on when this happens. Car Trouble Symptoms Can Indicate Minor or Major Car Problems. After my brake install I was told it would take a little while for a firm pedal because the brake pads need to seat. Scott 1642 Lawn Tractor Owner and Service Manual - Free download as PDF File (. Start your engine, but keep it in Park with the parking brake on. The new BMW M8 teams this innovative system with both the standard M compound brakes and optional M carbon-ceramic brakes. If so your rubber brake lines going to the front discs need to replaced. Then I disconnected the vacuum line from the brake booster and plugged it. Another important thing to remember is that brake fluid kills - paint jobs that is. Went to the store, there for 15 minutes, went to start car, pedal hard. Waste gate solenoid. Pedal goes rock hard after a few pumps when the engine is off, but still goes down when the engine is running. My Ford F250 4x4 brake pedal goes to the floor when you start the truck and stay's to the floor until you shut the engine off then it returns? The brake booster, master cyl, rotors, pads, brake lines, drums, brake shoes, and brake cylinders have all been replaced. Technician B says that there should be at least two power-assisted brake applications after the engine stops running. Master cylinder mounting bolts loose. Don't push like you are panic stopping, simply hold pressure like you are sitting at a red light. Whats happened?! Bad brake servo?. If you put your foot on the brake and then start the engine the pedal should drop slightly and become a bit spongy, once the vacuum has built up. Air in the system can also cause a soft brake pedal. If you pump the brakes a few times or hold them down a while after you've turned off the engine, you will "use up" that vacuum and the pedal will feel hard. I'm trying to narrow down the problems. ,bled lines,replaced brake lines,master cyl. If I plug the rear and just run the front, the pedal goes to the. Pump the pedal a few times when it's running and it's nice and firm for one pedal, then it's back to being a little spongy. You can easily inspect for a leak by looking under the vehicle. Also if I press the brake pedal hard enough it almost goes to the floor. Typically on first pump the brake goes all the way to the floor and will still grab hard enough to lock the tires in gravel right against the floorboard. 98 GMC C1500 Sierra 5. Problem: Brake drag or brake pedal slow return. The initialization procedure most be repeated 5 times to ensure any trapped air has been dislodged. Brakes pump up hard with no engine running and sink a little when engine started. Press the brake pedal firmly and run the Scan Tool Automated Bleed Procedure. I've changed the brake pads and twice and the rotors once so far and there is less pedal travel with new pads installed, but at times the resistance of the pedal changes when I press it far enough. That being the case you should feel the pedal go soft when you start the engine. Bench bled before install I have not installed the new rotors or pads in the front yet. Two technicians are discussing vacuum brake boosters. Does NOT cover engines with light alloy block or Ford Escort Twin Cam with Lotus engine. now after only 6 months the brake pedal is soft. Compare how far you can push the pedal at a stop with the engine running to how hard and far you push the pedal when driving and coming to a stop. BLEEDING THE HYDRO-BOOST Use only DOT-3 or better Brake. If you start the engine and press on the pedal, it gradualy goes about half way down. It was raining all night and foggy in the morning when I pressed the brake pedal and noticed it was spongy and went all the way with resistance and bad brake quality. with the engine off you deplete all the vacuum reserve and the pedal becomes harder. This symptom points to a few potential problems, all of which need to be fixed as soon as possible. I guess it's okay with 23,6mm mbc. After 3-4 times there wasn't any more air and the fluid was coming out crystal clear. new Booster, 3 master cyls, New calipers, New wheel cylinders in the rear. As the title suggests I have straight to the floor spongy brakes. With the truck moving, the pedal is soft, but the truck stops before the pedal sinks any significant amount. The truck stops really good now, it's just this low, soft pedal that's driving us nuts. goes to floor when running! I have a nice firm brake pedal when the car is not running, as soon as I start the engine, the pedal goes almost to floor. I had the DSC turned on for those two sessions and didn't run that for the remainder of the 2 days - it was triggering almost constantly for those two sessions though and because it doesn't like any. Could this be a master cylinder failure even though the pedal is firm without the engine running? The brakes do work but they feel. If I pumped the brakes a few times while stopping (to build pressure) it felt normal. The brakes were working fine. When I quickly release and reapply the pedal gets firmer and higher. The second test to run was to press on the brake pedal, engine off, and then start the engine. This procedure may use more than a pint of fluid per wheel. Learn How to Diagnose Your Chevy, Buick, GMC, and Cadillac's Problems with this Guide. Such a soft brake pedal problem can occur due to various reasons such as air in the line, holes in the brake lines or worn calipers. When the car is not running the brakes firm up after stepping on the brake pedal once. Booster Test: With engine off, pump brake pedal to evacuate vacuum in booster. It is odd b/c I didn't notice much (if any ) air bubbles at all when I bled the brakes just now. Re: Soft brake pedal with car running - Firm when its off Originally Posted by MikeWire One thing I noticed on the A4 calipers: If you crack the bleeder valve more than 1/4 turn, it seems to suck air back into the caliper and/or the line. The brake pedal is hard if you pump them up when endine is not running, and it stays firm as long as you hold pressure on it. But if what you are describing "the pedal is spongy one time, and firm the next" is different when driving with the engine running and driving it around then I'd favour the seals in the master cylinder are past their best. Refer to Tire and Wheel Removal and Installation. keen — May 3rd, 1996. He then started it up and pumped them again, and my brake pedal is good and solid. The only thing I haven't checked brake pedal servo drum pin to mbc stud clearence. The power brake for a Ford F250 operates with a vacuum booster. After that the pedal felt soft / spongy. Just wanted if anyof you have had problems with a soft brake pedal on an Octavia? Ive got two cars the same but on the brake pedal is firm both with the enigine on and off but the other is firm with the engine off but when you start it you can push the pedal almost to the floor!. Suggestions? I'm thinking a slow leak in the brake booster, but would like some other opinions before i start thinking about replacing parts. Plug rear brake port on master cylinder with engine running pedal solid. Air in the brake system can make your brake pedal feel spongy and vague. Can hear no vacuum leaks or engine changes. Electrical Circuit Repairs - High Resistance, Opens, and Shorts High Resistance, Opens, and Shorts. This action will fill upper and lower sections of valve rapidly. Have them hold the pedal half way down while the screw is closed. My daughter's 2004 GMC Envoy has had a soft brake pedal since we purchased it several years ago. eventually, I got a ok pedal: brakes apply after a couple inches, still sinks, but not all the way to floor, stops a few inches from floor ?!?. Odd that the pedal works with the engine off. The car stops acceptably, but lacks the firm brake pedal it had prior to the bleeding. 2 of which were VW dealers. I don't see how turning the engine on and off would make a difference since the brake system is closed and doesn't cycle fluid through it with the engine running. There should be only minimal travel in the pedal before the brakes are engaged, and it should not require significant effort to slow or stop your vehicle. test the booster with engine turned off, pump brake pedal until pedal goes hard then hold foot on brake pedal and start engine. Please help: Yesterday I changed the brake lines that run from front to rear on our 1997 Taurus LX with ABS. ,bled lines,replaced brake lines,master cyl. I then changed the master cylinder. I am running the 7/8" master cylinder and proportioning valve is wide open to the rears right now. lots of drivers and MOT testers ( during the brake roller test the wheels locked while the brake pedal was halfway down) were puzzled with this and. They couldn't explain it - but the brakes work fine when the van is moving. Have them hold the pedal half way down while the screw is closed. Still have brakes, but when doing an emergency stop tonight, the pedal went against its stops I think I've got a knackered master cylinder any thoughts?. Reconnect the vacuum booster hose and run the engine at fast idle for 10 seconds. How would this effect the brakes being spongy or pedal going to the floor? any further help will be appreciated. (If your vehicle doesn't. Bled the brakes twice and the pedal is still soft with the engine running. got home, let it sit for approx 1 hour, pedal soft. Ended up changing right front brake caliper due to broken bleeder valve. Pedal feel when road racing or open-tracking may be very inconsistent due to the vacuum level fluctuating from extended periods of wide-open throttle. If the pedal still has one or two assisted applications before getting hard to press, likely no leak exists. Took it back to the garage. now I dont have any brakes. The pedal can be depressed 1/4 of the way even after multiple pumps. Please read part one before continuing with this article. 98 GMC C1500 Sierra 5. No fluid loss. As for fuel consumption, the CFE gets 8. I've changed the brake pads and twice and the rotors once so far and there is less pedal travel with new pads installed, but at times the resistance of the pedal changes when I press it far enough. However , when the engine was not running the brake pedal was solid as a rock it was not going to move, just like it used to be,whether the engine was running or not. I got in the car and pumped the brakes to push the rear pistons back into the pads and start the car up and the pedal is just as low as it was before. ) If your vehicle has power brakes and stopping seems to take excessive effort, you may need to have the power booster replaced. Bench bled before install I have not installed the new rotors or pads in the front yet. Press pedal, does it stay hard ? If so start engine and press pedal, does it then creep to floor ? If it creeps to floor with engine running (diesel with vacuum pump) it is not unusual, some vehicles do this, (read my old posts there is a thread about an astra i think with similar) Do the brakes work ok in normal use ?. I then set up the bleeder as normal, filled it with fresh brake fluid and bleed the brakes normally going around the truck two or three times. It would stop no problem, even performed a few emergency stops but the pedal travel was to excessive. Still have brakes, but when doing an emergency stop tonight, the pedal went against its stops I think I've got a knackered master cylinder any thoughts?. A "soft," or "spongy," brake pedal describes a situation when the brake pedal does not have that firmness. After the last session of the day prior, I notice brake fluid has left the overflow line, there's a puddle on the ground.