Hydrovac Brakes Hard Pedal


I used the parking brake all the time, or at least until I couldn't push down the pedal. Re: Bleeding a Bendix Hydrovac equipped brake system. Improper operation, noisy system. If the pedal or linkage holds the master cylinder piston "on" slightly then the brakes will not release completely and can and will hold the brakes locked. it can go days or even a week with no issues then start acting up again. check first for a leaking hose at the booster. then i remembered TOWCAT had posted something about pedals and that i would need the f450 pedal assy or redrill existing pedal assy. You didn't say if it held vacuum after sitting (with the engine shut off) for a period of time. ) How this works: The master cylinder sends a signal to the Hydrovac; the Hydrovac has an engine vacuum source and diaphragm; like any vacuum booster, Hydrovac boosts the hydraulic pressure to the wheel. If your brake pedal does not maintain a firm and responsive feeling, a problem is present and your vehicle may not stop in a safe amount of time. When driving along the brake pedal goes hard and gets harder after pressing a few times then if i leave it for a few seconds seams normal again. If you add a vacuum booster to this type of car you will have a very hard pedal. I drive a 97 FLD120. Any suggestions. I believe this helps with the brake pedal range, but also makes the pedal softer. When I released the brake pedal, the sound again came. Simple fix, once the booster is fully installed, press the pedal, extend/pull the switch 'pistons' back out to full length, then gently release the brake pedal. When the pedal becomes hard the travel is only 1 to 2 cm but there is a perceivable difference in the feel. Finding the cause can be tricky, but is much easier with a logical approach. With the engine off, pump the brake pedal until it is hard. One pump and you're out of vacuum. The hard brake pedal has only happened in low speed parking lot situations, mostly backing into a parking space, but it has happened going forward as well. Not yours tho. All of a sudden, very hard pedal but no stopping power. The thing looks like it splits the front system between both. New master cylinder, new wheel cylinders, shoes, springs and drums. Even with a bad Hydrovac you still should be able to get a hard pedal, you just won't have any boost. I don't know how to test the hydrovac- hate to condemn a new part before testing. MC full of fluid. When reaching destination, I bled my brake system. The brakes will operate without the power assist unit, but the pedal pressure will be noticeably higher. The dash lights all come on. look at the piston on your photo. In the morning I pull my car out of the garage. When I brake normally, the brakes do not respond very firmly but I noticed if I really stepped on the brakes hard, the. When removing rear brakes they noticed uneven wear on brake pads, recommended resurfacing. Check the brake power booster by pumping on the brake pedal while the car isn't running. the pedal is hard but hell just putting in gear you can feel its weak and just going around the block 20 mph maybe omg i had to give it everything i had on the pedal to stop and. I suddenly pressed the brake and stopped the car, but the sound disappeared. AVOID DRIVING IN THIS CONDITION. I drive a 97 FLD120. Hard to get on! start with a corner and keep working at it and they fit perfectly. the vac line off the booster provides the boost assistance when you Press the brake pedal. Now start the car and pump the brakes. Basic function can be checked by pumping the brake pedal until hard with the engine off and then starting the engine while maintaining slight pedal pressure. A power bleeder makes it easier since it won't require an additional person to step on the brake pedal. If it is under 20 degrees outside, this happens when the car is first driven after sitting for awhile. Re: How to Tell if Brake Booster or Master Cylinder is Bad 05/17/2010 10:20 PM Just a FYI for anyone who may have problems, especially if they are having to pump the brakes to stop, or it will stop sometimes, and then other times it just goes strait to the floor (spungy feeling). The bleed screw closest to firewall will not budge! I put some penetrating oil on it over night so I will check again today. One factor may be heat. Sometimes you can't tell from looking at the outside of the hose for internal damage. But it’s time to upgrade to something. Sounds like you have a broken vakuumpipe for your brake booster. " If you mean it's difficult to stop the car, then you have a leak in the brake booster system. Your Chevrolet Corvette will be happy to know that the search for the right Power Brake Booster products you’ve been looking for is over! Advance Auto Parts has 8 different Power Brake Booster for your vehicle, ready for shipping or in-store pick up. If reserve less than 5", re-bleed Hydrovac and rear brakes in sequence outlined above Manual Bleeding: 1) Install adapter and automatic filler J-713. The pedal should go down a bit more beneath your foot. Have not pulled the wheels yet. Disc Front & Drum Rear: Power Brakes with Hard Pedal A hard pedal with power disc brakes front and drums rear could be caused by one or more of the following conditions: A defective power booster When a power booster goes bad the pedal will get extremely hard. The three types of vacuum brake boosters are the lever, disc, and tandem. The car shakes when I hit the brakes hard and it sounds. • If the brakes will not release on firewall mounted brake booster, disconnect the _hydraulic line to the wheels. Clutch Brake Pedal Hard Rubber Pads Rubber Foot Pads , Find Complete Details about Clutch Brake Pedal Hard Rubber Pads Rubber Foot Pads,Clutch Pedal Rubber,Rubber Brake Pedal Pad,Rubber Brake Pads from Other Rubber Products Supplier or Manufacturer-Hangzhou YarwinSun Technology Co. Depress the brake pedal lightly, without pushing too hard, and maintain constant pressure on the pedal. The sound is still on even with hand brake engaged. If, instead of remaining stable, the pedal moves down, lessening the reserve, it is an indication that the hydraulic system is leaking fluid. Hard to get on! start with a corner and keep working at it and they fit perfectly. After numerous attempts to get a hard pedal, the symptoms where that I could bleed the brakes get a hard pedal and then slowly rotate the rear wheel, apply the brake periodically, then all at once the rear pedal would go down about twice as far. I rebuilt the rear wheel cylinders in mythen tried to bleed and could never get a good pedal. When you start it, the pedal should sink a couple of inches if it works correctly. It has TWO SEPERATE units with a dual piston master cylinder. This feature is not available right now. Functioning well 2A brakes should stop you without a whole lot of pedal effort. All components of the entire brake system have been replaced with oem parts but they still feel soft. Brake fluid should be almost clear, with a slightly amber tint. JEGS power brake conversion kits transform your manual brake system to a power assisted unit. If the pedal is firm and hard, move to the next. Today I had the cruise control on and was going about 70 mph. Inspect disc brakes caliper piston boots for tears or deterioration. There is about 1/4" of "play" until you press too hard and the wheels will lock up and nosedive to the right. - If you have to stomp on your foot-pedal starter, either you, or your starter, or your engine, has a problem. The brakes can still be used when the brake booster fails. If your pedal is hard before crank AND the pedal wasn't pressed after the engine was cut off AND it's only been overnight get it serviced, something is wrong. Over time, this causes sludge to build up in the brake system, and this sludge can make it seem like the brake booster has failed. If the pedal is firm and hard, move to the next circuit. If the hydro-vac is bad the brake pedal will be hard and high (no assist). You will have a very hard pedal if you’re using a bore larger than 1. Call Us Cart (). Brake pedal on my 99 GC is pretty stiff. Are there any brackets or clips,etc. A rock hard pedal is normal for a manual brake A body, at least the ones I've had, and the ones with disc brakes were worse than normal. International Harvester S1954 7. Proper operation should result in the brake pedal sinking down and then pushing back up against your foot. As the problem with the vacuum brake booster check valve increases, air bubbles will progressively move down the brake lines and to the brakes themselves. Over time, this causes sludge to build up in the brake system, and this sludge can make it seem like the brake booster has failed. The brake pedal going to the floor would indicate brake fluid leaking past the seals somewhere in the braking system. I have read calipers can cause a hard pedal but thought I'd ask the board first. Is there a replaceable seal or gasket somewhere that would leak the vac once the pedal is depressed?. When the pedal is soft and spongy, your braking system is not functioning at 100%. If your fluid levels are dropping look for fluid leaks at all 4 wheels. I start to go down the highway brakes are working fine. Two smaller diaphragms equal the same assist as one larger diaphragm does. I have a 68 with power disc brakes. INDEX SPECIFICATIONS: Page Air brakes •. Over 600K Auto Restoration & Performance Parts. The truck has 90k miles on it and this is the first issue I've had with it. It draws that air from the other hose that goes up to the air cleaner. The diameter and length of the master cylinder has a significant effect on the performance of the brake system. If your push rod isn't the correct length, it can cause issues, like a soft car pedal. I think Rocky's theory sounds good, but it's always been my experience that a hard pedal is the result of a collapsed brake hose. Then about 5 minutes down the road the brakes worked fine. See all problems of the 2010 Ford Edge. Discuss it at Forum View Details. Good for Lift kits because of extra length at 4". When you start it, the pedal should sink a couple of inches if it works correctly. A larger diameter master cylinder delivers more hydraulic fluid to the caliper pistons, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. A variation on the low and hard brake pedal complaint may also occur on vehicles equipped with disc brakes. Bleeding removes the air from the brake lines. How To Fix A G29 Brake Pedal Maxing Out At 75-80%. I've also seen just a slight leak that would work OK as long as you didn't pump the pedal. so my brake pedal is really getting hard to push these days I have changed out the rotors, but havn't bled them or anything the pedal is really QUITE hard to push. There is a diaphragm inside of the brake booster if the diaphragm is leaking suction. If no action is felt, the vacuum system is not operating properly. view details; sep 27, 2018 - grandview, tx - service brakes. Hydro-boost brake systems are self-bleeding if there is no other problem in the system. There is about a half inch of play. But first half of brake pedal travel became soft, without real brake power. Reader Question Hello Austin,. 2 sovereign. The hazards:  if the brake pedal becomes loose or inoperative, the driver may be unable to stop the vehicle by using the brake pedal. Saab pn 12847287. (A Bendix Hydrovac was popular on 1950s bread trucks, vans and medium duty trucks with hydraulic brakes and a through-the-floor brake pedal. Re: Bleeding a Bendix Hydrovac equipped brake system. If the pedal remains firm then the master cylinder is good. I've brought it to the dealership and they can't find anything wrong. If you step on the pedal and feel a vibration, you're in for some troubleshooting. When I brake normally, the brakes do not respond very firmly but I noticed if I really stepped on the brakes hard, the. I got rid of that truck because I never felt confident in the brakes. And to find partners which are "compatible". The hydro-boost generates a different pedal feel than a vacuum booster. He's referring to, what sounds like something from the 80s or earlier, gotta be firm with the truck. I suddenly pressed the brake and stopped the car, but the sound disappeared. I couldn't tell if it was the pedal that was causing the problem, or something in one of the lines. Very dangerous. Original factory part c9zz-2455-c, for manual non-power brakes with a t automatic. Sounds like it may be the same as my (assumed) vacuum leak. It should feel just as easy to press as the other two pedals on the floor. and once the engine is turned on, the brake pedal again, is easy to press down. If your brakes are not adjusted properly the master will pump up and seem to be hard. I asked Wifey to come out and step on the brake pedal when I said OK. See all problems of the 2010 Ford Edge. Online shopping for Hydrovac Units - Brake System from a great selection. The best fix I've found for this is a manual disc brake master cylinder, Cardone part number 10-1523, for a 1974 Charger with a 318. This is the "coaster" part. Service, parts, cost & recommendations from YourMechanic. I did some brake work on the rear axle, driver's side. This feature is not available right now. I think Rocky's theory sounds good, but it's always been my experience that a hard pedal is the result of a collapsed brake hose. Take a look at your brake system and see if any of these are causing the problem. If the brake pedal is hard to push, the problem is most likely in the power assist. 5l gtdi - inoperative, excessively noisy vacuum pump, hard brake pedal on initial start-up and/or open fuse f64 in the battery junction box ford: 2011-2012 f. They bleed just fine, the only problem is when I'm all done, the pedal only pushes down a few inches and it's rock hard. About 4 days ago, the brake pedal started to get very hard to push , (as hard as when the engine is switched off) and wasn't stopping the car very well. The last few days I noticed the brake pedal is harder than normal when I start the car (but it started and ran fine). Brake fluid shot the entire length of the truck so there doesn't appear to be any restriction inside the unit itself. Separate the master cylinder from the mounting studs. A very hard pedal which will not stop the car. I pushed my foot on the brake and hit the ignition button but it wouldn't turn - it tried, but didn't make it. Reader Question I have the same 98 Chev K1500 with ABS which sometimes, only at slow speeds, activates the ABS, actually pushing back on the brake pedal. Hydrovac Problem: To buy new, surplus, or repair My hydrovac is starting to give me problems. When driving along the brake pedal goes hard and gets harder after pressing a few times then if i leave it for a few seconds seams normal again. Only a pressed brake pedal stops this sound. However, if pads are contaminated with oil, dirt, or other substance, then it causes brake pedal vibrates during the clamping of brake pads onto. use a small diameter booster such as a 7" street rod booster for a heavy car you will get a very hard pedal. Also, on some trucks you might not be able to completely slide the clutch pedal out, which is a necessary step. Once she starts all is fine. this problem is not always. Any ideas would be helpful. When you apply the brakes, air is exhausted from the cylinder head of the piston. Its always unnerving and I usually respond by pressing hard on the brake. Turn steering wheel lock-to-lock 5 times. HYDROBOOST TROUBLESHOOTING. Even with a failed booster you wouldn't have an extreme hard pedal, just more effort to apply brakes. Overheated brakes is a very dangerous situation which can cause old or contaminated brake fluid to boil. I guess I need to replace the booster, right? No. A rock hard pedal is normal for a manual brake A body, at least the ones I've had, and the ones with disc brakes were worse than normal. I noticed starting last week that my brake pedal was rock hard before i started the car then returned to normal feel once its running. Sounds like you have a broken vakuumpipe for your brake booster. Brake fluid should be almost clear, with a slightly amber tint. Once she starts all is fine. HARD BRAKE PEDAL • Check for engine vacuum, make sure manifold is open and clear of carbon build up. 2 sovereign. So I went and changed the wheel cylinders and shoes. I have a very hard brake pedal on a 71 dart,manual brake car. I can't find a metering device. So no relevant codes were recorded for this, and when you look up hard brakes, or reduced brake function, DAS pretty much says to just have a look at the brake booster. I don't find any decrease in braking performance, till now. Remember, if your car is equipped with ABS (most are these days), the pedal will seem to vibrate when you brake very, very hard. Please read part one before continuing with this article. If you do not feel comfortable bleeding your brakes or can not get a consistent and firm brake pedal we recommend taking your VW to a qualified professional. its a 1994 camaro strange Manual Brake Conversion Kit all 3an braided brake lines front to back aerospace front drag brakes stock disk brakes in rear i bled the brakes and went back just to make sure did all 4 again. This feature is not available right now. BRAKE SYSTEM L-UNE MOTOR TRUCK SERVICE MANUAL. There is a simple way you can check its operation yourself. I replaced the rear pads and looked at the front and they looked ok. brake pedal feels hard to push and have little braking at normal road speed i have changed front and rear pads done a complete change on the fluid and changed 1 caliper that the rubber had all twisted up. Reader Question Hello Austin,. If the brake pedal is hard when the engine is running, then there's a problem. This sound is related to the brake pedal for sure. Review (mpn: c9zz-2455-c for sale) C9ZZ-2455-C 69 70 1969 1970 Ford Mustang Mach 1 Cougar Xr7 Drum Brake Pedal Auto C4 Fmx C6 C9zz-2455. If you then keep your foot on the pedal and switch on the engine the pedal should go down. You will have a very hard pedal if you're using a bore larger than 1. It should feel just as easy to press as the other two pedals on the floor. If it is the hydrovac is a repair kit from Rex Ward the way to go. Step on the pedal and hold pressure for about 30 seconds. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them. The brake pedal should be an inch higher than your car's gas pedal. We showcase a varied catalog of products ready to ship at competitive pricing. Did rear pads last night as they were finished. Soft or spongy brakes can be frightening, but you can usually correct the problem without too much hassle. 1999; More Service Bulletins of Other 2000 Mercedes-Benz Mercedes-Benz Components. If you are talking about a hard brake pedal during normal driving situations - It sounds like you might be having a power brake booster issue - One simple test you can try while sitting in the drivers seat - (Engine Not Running) Depress the Brake Pedal a few times and hold it down, start the vehicle while holding the brake pedal, when the vehicle starts, if the brake pedal falls away (Goes. It certainly does - and working perfectly. Leaks in the brake booster provide a vacuum leak to the engine. When you first hit the brake pedal, the pads don't generate much braking until they are held for a couple of seconds. Hope somebody can help. I checked the vacuum booster line and the check valve at the booster, both seemed fine. I don't know how to test the hydrovac- hate to condemn a new part before testing. How to Test For a Bad Brake Booster / Brake Booster Testing - Duration: 10:36. Hold at 2200 rpm for 15 seconds then allow engine to return to idle. Engine dies when brake pedal depressed Mga sir, ano kayang problema nito? Ok ang idle ng car ko pero pag inapakan ang brake, patay ang makina. Soft or spongy brakes can be frightening, but you can usually correct the problem without too much hassle. By continuing to use this site you consent to the use of cookies on your device as described in our cookie policy unless you have disabled them. The manual system had an unknown bore diameter (we think it was 1 inch) and a stock underfloor brake arm (a '39 Ford-style brake arm). The pads were replaced about two weeks ago. Disc Front & Drum Rear: Power Brakes with Hard Pedal A hard pedal with power disc brakes front and drums rear could be caused by one or more of the following conditions: A defective power booster When a power booster goes bad the pedal will get extremely hard. Use this initial bleeding procedure whenever replacing or servicing any component in a hydro-boost system. Pumped it a few times and got brakes. I have also bought an rs tuner and abs software. Usually within 30-45 minutes the light goes off and brakes are fine again If there is a trick to get the brakes to come back to life quicker i'd like to know as well!!!. Did rear pads last night as they were finished. Pressurized fluid also flows through the hydro-boost to the steering gear to provide power steering. Pedal slowly sinking would be a leak in the system, a failing master cylinder or contaminated brake fluid. When you step on the brake pedal, the master cylinder moves fluid through the lines and hoses to the wheel cylinders or disc brake calipers, which moves the shoes or pads against the rotating drum. Original factory part c9zz-2455-c, for manual non-power brakes with a t automatic. A coworker mentioned that his brake pedal on his 2015 Sierra would get rock hard when he would be on the brakes easing up to park as close to another vehicle in his driveway. This can lead to accidents if not corrected. I noticed that brake pedal is so hard that I need to put significant amount of force to stop the car. The truck stops just fine empty or with 100 bushels, but with a full load you might get somewhat of a good first application, but after that you can stand on the pedal and barely slow it down. Did rear pads last night as they were finished. I quickly nursed it home. If You Have the Horsepower, You Should Also Have the Brake Power! There are a lot of street rod brake items in the market place today. Engine dies when brake pedal depressed Mga sir, ano kayang problema nito? Ok ang idle ng car ko pero pag inapakan ang brake, patay ang makina. Once she starts all is fine. Separate the master cylinder from the mounting studs. The new one seems to be leaking a bit as well…. Philips Avent Anti-colic Baby Bottles Clear, 9oz 3 Piece,Pedal It!: How Bicycles Are Changing the World by Michelle Mulder (English) Hard,VIGOUR bodybuilding muscle magazine/Julian Creus 10-47 (UK) vol 2 #10. Brake Basics for Street Rods. Once in a while, My 87 YJ brake pedal will feel hard as a rock then I hear a pop, then the pedal feels normal again. The clutch problem you talk about is totally. Then about 5 minutes down the road the brakes worked fine. You did not lose your brakes all at once-----but you would gradually lose the power side of the brake system (as Loadstar was explaining). No matter how hard you pushed on the pedal, it didn't seem to make any difference in its ability to stop the car. 10-20 degrees. There is a diaphragm inside of the brake booster if the diaphragm is leaking suction. It draws that air from the other hose that goes up to the air cleaner. With the booster hooked up to vacuum, they grab hard with just a slight touch. Problem:Brake Pedal is rock hard. The power brakes won’t have as much power as it used to. Over time, this causes sludge to build up in the brake system, and this sludge can make it seem like the brake booster has failed. Also, the brake booster does not store vacuum after the engine is shut off that's why it's hard. At this point, the pedal becomes hard as the booster has done all it can but the vehicle still needs more. Lubricate rotating and sliding components with a rubber compatible lubricant. the brake pedal. I thought it had something to do with the master cylinder so I replaced it because it was leaking. The item “Bendix Power Brake Booster HydroVac 1979-83 International Harvester IH Truck OEM” is in sale since Thursday, April 25, 2019. Good for Lift kits because of extra length at 4". Re: Hard brake pedal at times. like i said, this is new has been only doing it for two weeks. I would like to fix what ever is broken. Bleeding A Hydrovac Brake System, Manual Manual bleeding requires filling the master cylinder reservoir and pumping the brake pedal to force the fluid through the lines to expel air from the system. When you open be bleed valve, does the fluid flow solid when brakes are applied? If yes then the problem will be on the hydrovac. Review (mpn: c9zz-2455-c for sale) C9ZZ-2455-C 69 70 1969 1970 Ford Mustang Mach 1 Cougar Xr7 Drum Brake Pedal Auto C4 Fmx C6 C9zz-2455. Braking power seem much-reduced, too, to the point where I can't drive the car. But, as it's been sitting for quite. The wheels of a bicycle, lifted off the ground and spun by hand, should spin freely and stop only after several revolutions. Hi peeps, Have changed my front discs and pads in June, all good. HARD BRAKE PEDAL • Check for engine vacuum, make sure manifold is open and clear of carbon build up. If you step on the pedal and feel a vibration, you're in for some troubleshooting. Even with a bad Hydrovac you still should be able to get a hard pedal, you just won't have any boost. The brake problem for Keenan's '34 Vicky was an extremely hard pedal. Pump brake pedal firmly 25 times. Pedal has been getting harder and harder of late, and to get the same stopping power I need to press it twice. Search our online brake booster catalog and find the lowest priced discount auto parts on the web. I have replaced the master cylinder and hydrovac on a 64 f-600. And when it does go back to normal the brake pedal go to the floor giving of a hissing noise. Just finally install my DCR E1, Ported manifold and max fab 3" and drove to the store not even in boost. (International, Ford, GMC, Isuzu). Hydro-Boost Tips & Hints All power steering pump operated power brake boosters. Any ideas would be helpful. Hard to get on! start with a corner and keep working at it and they fit perfectly. When I brake normally, the brakes do not respond very firmly but I noticed if I really stepped on the brakes hard, the. Therefore this is normal. Pump the brake pedal five or six times. With the booster hooked up to vacuum, they grab hard with just a slight touch. Now this event is not consistent, its happening randomly, i did observe its happening only on low speeds and in stop and go traffic. Check booster operation by applying and releasing the brake pedal with the engine off to deplete the vacuum in the booster. Today I had the cruise control on and was going about 70 mph. I've also seen just a slight leak that would work OK as long as you didn't pump the pedal. 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. I drove it home about 8 miles like that and tore the front brakes down. The pedal is hard when pumped with the van off but travels and is mushy when car is turned on. On the rear I have an 11" Ford explorer setup (single piston). Unit had no brakes when I started- got alot of air out- now a 3-4 pump then there's a low hard pedal. 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. How To Fix A G29 Brake Pedal Maxing Out At 75-80%. Hello all! I have a 2014 R/T w/17K miles and when I went to take my car to work this morning, after being warmed up with remote start, I got in car and started it and the brake pedal was hard as a rock and the anti lock light was on. Of all the Mopars I've owned that one had the best brake pedal feel. Also, the brake booster does not store vacuum after the engine is shut off that's why it's hard. In the morning I pull my car out of the garage. Brake fluid is not extremely hot. Like stepping on a brick! To check your booster, turn off the engine and step on the. Re: How to Tell if Brake Booster or Master Cylinder is Bad 05/17/2010 10:20 PM Just a FYI for anyone who may have problems, especially if they are having to pump the brakes to stop, or it will stop sometimes, and then other times it just goes strait to the floor (spungy feeling). Usually, however, the problem is a vacuum leak causing the brake pedal to be pulled downward causing the car to drag or outright stop. With her foot still on the floor, I re-connected the line, then. When I press the brake pedal (engine off)there is a noise that sounds like hydraulic pumps running, it also occurred when I shut the engine off. This is the "coaster" part. The factory used a short pedal with these factory installations. DOES YOUR BRAKE PEDAL PUMP UP HARD THEN AFTER A LITTLE TIME GOES BY LOSE ALL IT'S PRESSURE? The problem here is your brake adjustment. Drivers only need to lightly apply the brake pedal to stop the vehicle. I checked the vacuum booster line and the check valve at the booster, both seemed fine. This happened immediately after, before I'd turned the car back on. A larger diameter master cylinder delivers more hydraulic fluid to the caliper pistons, yet requires more brake pedal force and less brake pedal stroke to achieve a given deceleration. We had the modern brake lining replaced with a softer material and it works fine now. The deal is that every once in awhile I'll press the brake pedal and it will be hard as a rock, but then subsequently go back to normal. Went to work this morning and brakes were still hard to press down. Lubricate rotating and sliding components with a rubber compatible lubricant. A brake pedal that is lower than normal is annoying and dangerous. There is a diaphragm inside of the brake booster if the diaphragm is leaking suction. 6L l6 Diesel Turbo. And yes; I know exactly how an automotive braking system works. Hydro-boost brake systems are self-bleeding if there is no other problem in the system. My 407 diesel coupe has a problem with the brakes. My concern is if the vacuum leak is occuring while the car is running becuase if so then unfilterd air could be making its way into the engine. Yes, bled the hydrovac. When driving along the brake pedal goes hard and gets harder after pressing a few times then if i leave it for a few seconds seams normal again. I spent quite a while looking through your site trying to find a posting from anyone dealing with my issue. To install a big brake kit may also require fitment of larger diameter wheels and tires. Unit had no brakes when I started- got alot of air out- now a 3-4 pump then there's a low hard pedal. tried havin someone pumpin the brakes and nothin. The last few days I noticed the brake pedal is harder than normal when I start the car (but it started and ran fine). If the hydro-vac is bad the brake pedal will be hard and high (no assist). A common cause of a hard brake pedal is a sticking brake pad or shoe. Fortunately, most things that cause brake pedal pulsation happen in the service bay. If there is air in the system, the stream will contain bubbles and may kind of sputter.