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I have done everything that I can think of to get pressure And nothing is working. It started with a seizing front caliper I replaced the caliper with a used unit and works fine I also installed new brake hoses and new rear wheel cylinders then spent several hours bleeding brakes. I have good solid brake pedal but only after pumping the brakes twice when car is off. As soon as I start the car the brakes go to the floor and I have virtually no pressure until I pump the brakes and then only some brakes after it gets near the bottom of the several strokes
Wow, that's different. There are only a few things left to try. To keep from buying unneeded parts first try bleeding this way one more time.
Do the longest brakeline first, then next longest, until you work your way to the shortest line. Then try it.
Now for a difference when starting the engine, your Brake booster is working. You should have a Reserve of Vacuum in the booster for at least one pedal depression. If you don't, the Booster valve or Booster Bladder is bad.
The Booster valve is relatively cheap. Test the booster bladder; you do not want to use a chemical. With the engine running, some people will use a torch propane tank with a rubber hose on it to direct propane around the Brake booster. The propane will cause the engine RPM to change indicating a bad bladder. Propane is safe in small amounts and was used to set air/mix in the early days of Pollution control.
The Master cylinder could have pulled in sediment when the old parts were removed from the system. Now it is hanging up.
For bleeding brakes there are different methods. I prefer to draw fluid with a hand Vacuum pump like a Mighty Vac. The advantages are it is less messy and far more controllable. Pumping a defective Master cylinder may not work for you. Power bleeding with a Canister and Master cylinder cap adapter will be better than relying on the Master cylinder alone. Gravity bleeding works, but may not work with a bad Master cylinder leaking more fluid in one chamber than the other.
Check for hose twists in the rubber lines you replaced. The ridges on the hoses should be parallel when you hang the caliper.
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I had that on my Acura. It was caused by warped brake rotors.
They may not have replaced the rotors on your brake job.
Brake rotors are usually warped by someone tightening the bolts too tight.Most cars require a torque setting of 80 to 120 ft lbs.
I've seen them torque the bolts to 300 ft lbs. So you have to watch anyone working on the wheels.
Hope this helps.
I have never had one brake issue in 49 years, of doing my own work
So the answer is-- you have not found a shop or mechanic, that knows how to work on or diagnose a brake issues & the best part is- brakes are fairly easy, no matter what has to be done
I would guess that either side rubber flex brake hose is restricted & should have been replaced for safety reasons, when the car was about 12 years old
Add to that- calipers that are rusted inside
Then- never changing brake fluid every 2 years, more rust inside EVERYTHING
Add-- never removing rust from anything that moves or slides & never lube anything- because that is what you get when you pay for brake service
Hi:) Sound like the brake pad need to be taken out and the caliper need to be wire brushed to clean them and anti-seize greased be for you put them back together they get road dirt on them and don't work after a few years.
If the caliper is seizing and it is not the caliper it is the module that controls how the brake fluid is distributed. I don't have my book in front of me at the moment but when you look under teh hood on teh drivers side you will see a block that has the brake lines coming out of it. That is part of teh ABS system is one is installed and is a master brake control hub if it ABS isn't installed. being that new I would assume it was equipped with ABS. There are a couple of ways you can test if this is teh problem. If I remember correctly the MPV brakes with all 4 brakes, that means you can, as a temp test, switch the lines to see if the caliper problem changes to the different caliper. If it does then you know for a fact it is that unit and not the caliper. Also, something to consider, the caliper that is locking maybe locking because the problem is actually the caliper on the opposite side. If the caliper on the left front is stuck in the open position, on occasion that will cause too much fluid pressure to the right front giving you the impression the problem is the right side and it isn't. This is rare but certainly a possibility. As a general rule you should always replace Calipers in pairs. If you replace the right front you should replace the left front, same with the rear calipers.
Check there is pressure coming out of master cylinder to front brake circuit If there is open bleeders on calipers if pressure there calipers are seized if not renew flexible hoses on front struts & bleed brakes
the shoes not being adjusted properly or if one shoe has more pad than the other like a primary and secondary them wrong will also create this issue, also brake fluid on drums and shoes.
It also sounds like a more likely problem is a seized caliper on the left side. If a caliper seizes, the braking system transfers the pedal pressure to the other caliper thus, the working caliper locks up. Pull both front wheels and look carefully at the wear on the pads. Both wheels should have the same amount of wear. If one side is worn more than the other, the side with the least wear is seized and needs to be changed.
Never heard of a hydraulic repostioning valve, but maybe with ABS there is one. I do know of a proportioning valve which apportions brake pressure front to back and also blocks braking to front or back in the event of brake line failure. Maybe see which he is talking about, should be able to explain the difference. Hope this helps.
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