4 Wheel Disc - Cant get pressure to rear brakes.
#1
4 Wheel Disc - Cant get pressure to rear brakes.
So I was having this problem where out of nowhere the pedal would go to the floor. Then id pump it back up quickly and it would come right back. I figured it was the master I swapped the master and attempted to bleed the brakes when I bleed the fronts which are the ls1 brakes from bigbrakeupgrade.com the pedal drops a ton. When I go to open the rear there is very low pressure and the pedal hardly travels down. I kept cracking the lines all the way to the master and still cant get the pedal to drop when I opened it. So I figured I had a defective new master and swapped it out again. Same issue. I did notice if I pumped the e brake a few times, oddly id get a little more pressure in the back. So I thought that was fine so I road tested it and was fine at first but then the "brake light" comes on and off and the pedal is just mush. Not going to the floor like before but just a real crappy pedal. Thoughts?
#2
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Re: 4 Wheel Disc - Cant get pressure to rear brakes.
Rubber brake hose at the rear axle pumpkin
#4
Senior Member
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
The other idea is, you have crud in a brake line that is choking the system.
#5
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
I’m having a similar issue on my car but I haven’t got around to diagnosing yet since the cars apart for ls swap/paint. I switched to 4th gen rear and replaced all hoses but couldn’t ever get any real pressure to the rear. Im gonna look into it when I get the car back together. I was assuming I had a master cylinder issue.
The only thing I can suggest is to do what I plan to do first and that’s just to keep bleeding them and maybe you’ll get somewhere.
The only thing I can suggest is to do what I plan to do first and that’s just to keep bleeding them and maybe you’ll get somewhere.
#6
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
I’m having a similar issue on my car but I haven’t got around to diagnosing yet since the cars apart for ls swap/paint. I switched to 4th gen rear and replaced all hoses but couldn’t ever get any real pressure to the rear. Im gonna look into it when I get the car back together. I was assuming I had a master cylinder issue.
The only thing I can suggest is to do what I plan to do first and that’s just to keep bleeding them and maybe you’ll get somewhere.
The only thing I can suggest is to do what I plan to do first and that’s just to keep bleeding them and maybe you’ll get somewhere.
yeah i bought the attachment for my pressure bleeder for that master. im gonna try to pressure bleed it first.
#7
Senior Member
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#9
Senior Member
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
Bench bleed level, put plugs in the outlet ports, push on the cylinder and measure travel. That will be a good indication all the air is out. A new OEM MC had a spec of 1/8" free play travel - by the Haynes manual (take that for what it's worth ).
#10
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
*IF* there is still air in there, I don't think that will get it out installed. The master is installed with too much angle to make sure you would get all the air pockets out - none of the outlets or inlets are located remotely near the top of the bore. Doesn't matter the method - it's about how it sits in the car.
Bench bleed level, put plugs in the outlet ports, push on the cylinder and measure travel. That will be a good indication all the air is out. A new OEM MC had a spec of 1/8" free play travel - by the Haynes manual.
Bench bleed level, put plugs in the outlet ports, push on the cylinder and measure travel. That will be a good indication all the air is out. A new OEM MC had a spec of 1/8" free play travel - by the Haynes manual.
i dont think my problem i in the master
#14
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
Well that’s definitely different than my issue. My pedal feels fine I’m just not getting full pressure to the rear brakes. It doesn’t sound like bleeding is your answer
#15
Re: 4 Wheel Disc - Cant get pressure to rear brakes.
Get someone to pump the brakes and hold pressure, then crack the fitting loose on the out side on the line to the rear brakes. Is there flow, and if so how much? Just a trickle or a good stream?
If you have a good stream it means there's an issue between the prop valve the the rear calipers. If no flow or weak flow, you've got a problem between the prop and the master.
Sounds like there's a bad prop valve...
If you have a good stream it means there's an issue between the prop valve the the rear calipers. If no flow or weak flow, you've got a problem between the prop and the master.
Sounds like there's a bad prop valve...
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