1Mtmind Posted June 8 Report Share Posted June 8 (edited) Just replaced the brake booster again. Did it 4yrs ago cuz the pedal was going to the floor and it was making a hissing sound. The first came with the master cylinder and I bled them. Things were good. Started doing the same thing. Pedal going to the floor with the hissing sound when it was released. New one didn’t come with a master cylinder so brake line weren’t disconnected. Pedal still goes to the floor. Pedal feels strong when car if off. After starting it goes to the floor. Could it be the master cylinder or check valve? Where is the check valve? It is the part that goes into the booster? That hose runs from the intake to the booster and then from the booster to the air tube after where the MAF sensor goes? Very frustrating. Do the brakes have to be bled after swapping the booster even though I did t disconnect any brake lines? When the car it running I can disconnect the vacuum line I take tube and I can feel it suck but I have no pedal. At my whits end please help Edited June 8 by 1004ron Quote Link to comment Share on other sites More sharing options...
garycrist Posted June 8 Report Share Posted June 8 @1Mtmind, Lets go back to the beginning. 1.Pedal went the floor. Replaced Booster and Master. Thing are OK. 2 Failure again with pedal going to the floor. Replaced Booster . Still the same. So master is bad or air in the lines or no fluid. The hissing sound is because the pedal is too far bleeding the vacuum inside As a side note from Ford a long time ago when one could see the fluid in the master cyl. was to have assistant pump the brake up 10 times and hold down. 2nd. person opens top of the master to observe the fluid level. Release the brake pedal. If there is air trapped the fluid will gush like a geyser from the master, indicating witch 1/2 of the system has air trapped. Quote Link to comment Share on other sites More sharing options...
1Mtmind Posted June 8 Author Report Share Posted June 8 So maybe the last booster and master went bad. I changed the booster again because it was doing the same thing as before. When all along it could have been the master and that got changed. Hmmm I’ll bleed the brakes tomorrow and see if that changes anything. I’d hate for it to be a defective booster. Meaning it’ll have to be reordered, taken back out and reinstalled. Everything went back together fine. Had a little trouble getting all four studs lined up into the firewall. Brake light switched work as it should also. Fluid is full with no leaks. Front rotors and pads do need to replaced. Pads are very thin. That’s next on the list followed by both front cv axles. Ugh. Just had to pop in one new coil a month ago. Swapped all the plugs too while it was opened up and accessible. Just put new rotors and pads out back two months ago. Quote Link to comment Share on other sites More sharing options...
1Mtmind Posted June 9 Author Report Share Posted June 9 (edited) On 6/8/2024 at 4:32 PM, garycrist said: @1Mtmind, Lets go back to the beginning. Just bled the brakes with zero bubbles. So I’m assuming a bad master cylinder or a faulty new booster. This is very frustrating. Edited June 9 by 1004ron Quote Link to comment Share on other sites More sharing options...
1004ron Posted June 9 Report Share Posted June 9 The first step would be to bleed the brakes without the engine running i.e. no vacuum for the booster. Quote Link to comment Share on other sites More sharing options...
garycrist Posted June 9 Report Share Posted June 9 You do know about adjusting the rear disc brakes with the emergency brake? Quote Link to comment Share on other sites More sharing options...
1Mtmind Posted June 15 Author Report Share Posted June 15 On 6/9/2024 at 4:46 PM, garycrist said: You do know about adjusting the rear disc brakes with the emergency brake? I just watched a video about. It said bleed the rear as usual. Then pump the brakes, hold, push and release e brake 5 times. Bleed each rear again. Then front. New master is arriving today. Hoping to get it done tonight. 1 Quote Link to comment Share on other sites More sharing options...
garycrist Posted June 15 Report Share Posted June 15 Do bleed the Master 1st.!!!! I do hope it works for you too! GL Gary Quote Link to comment Share on other sites More sharing options...
1Mtmind Posted June 16 Author Report Share Posted June 16 On 6/15/2024 at 11:10 AM, garycrist said: Do bleed the Master 1st.!!!! I do hope it works for you too! GL Gary Unfortunately something went wrong along the way. After taking it out and swapping over the reservoir. I filled it, clamped it in the vise, and pushed in the plunger a good 75+ times. Pressure got real hard to push in. Thought I was good. I don’t know. Bought a bleeder vacuum kit. Was only getting bubbles. Switched to manual bleeding with two people. Got a couple bubbles. Did the e brake cycle. Three times. Every time after the first it was good fluid no bubbles. When it’s off the pedal doesn’t stiffen up after 1 or 2 pumps. It stays a bit soft. When it’s on, the pedal goes to the floor. I’m not leaking any fluid anywhere. Now it has a new booster and master cylinder yet nothing has changed. I’m wondering if I have air in those flexible brake lines between the master and the distribution block. I saw where you can crack each line loose one at a time until the drips turn into a steady stream. Then tighten it. Quote Link to comment Share on other sites More sharing options...
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