Brake master cylinder runs dry

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pignosedslut
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Master cylinder goes dry after a day. I'm not bleeding it or anything, its just sitting right now. Could it be leaky brake lines? Master cylinder?


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asoomal
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How many miles are on the vehicle? The brake master cylinder typically do go out at around the 180,000 - 220,000 miles mark.

Inspect the area behind the brake master cylinder, where it attaches to the brake booster. Are there any signs of brake fluid there?

Also check the foot well area around the brake pedal shaft.

pignosedslut
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178k km. I put fluid in again to see if it would leak out and it seemed to leak out the bottom of the brake booster which looks like master cylinder to me. The previous owner said he bled the back brakes but the fronts wouldn't bleed. How would he be able to bleed the backs with a faulty master cylinder?

wa-chiss
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The master cylinder is leaking into the booster. You'll need a new master cylinder and most likely a booster now. Booster diaphragms don't like brake fluid one bit.

pignosedslut
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You guys think the previous owner just lied about being able to bleed the backs and not the fronts?

wa-chiss
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Not necessarily. If there's a blockage in the bleeders or the fluid is so contaminated that the lines have rust in them then it might not bleed. It's not uncommon on older cars to have these issues.

pignosedslut
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It has Skyline brakes in the front with braided lines the guy before me put in. He gave me another set of calipers. He thought they werent bleeding because the caliper was maybe seized (??)

pignosedslut
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So I'll need to get the master cylinder and the brake booster. You think I should swap the other calipers over see if theyll bleed, if not it's probably my lines?

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asoomal
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Try the master first, booster may still be fine.

wa-chiss
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asoomal wrote:Try the master first, booster may still be fine.
From my experience, it's best to just go ahead with a new booster also. The car is already 20+ years old, the diaphragm is jelly by now.


Replace both the booster and master cylinder. Take the calipers off and try to compress the pistons with no lines hooked up and the bleeders out (it should be easy with the lines and bleeders off). If they don't move, they're seized. You can try to rebuild and hone them, or replace. If the pistons move freely, then there's a good chance the blockage is in the lines. If so, try pressing the brake with the calipers off to see if you get fluid to come out. If no fluid comes out, my bet is the braided lines depending on the manufacturer.

pignosedslut
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Thanks a lot. I appreciate it. I have another set of caliper to try too. Just need to find a day to go out and buy the master cylinder and booster. Thanks for all the help guys.

pignosedslut
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Hey guys, waiting for my parts to come in. Could a faulty master cylinder cause hardcore brake drag? Cylinder is dry and pedal goes to the floor.

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centralcoaster33
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Yeah, it could do that. Per what I read above, you really need to get your brake system sorted out. I see you're still driving the car like this for months. I hope you get your parts soon. I hope you drive accordingly safe so as not to endanger others on the road with your car's poor braking ability.

pignosedslut
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:rotfl Don't worry, I'm not driving the car. More of a project. Need to figure out the brakes asap though.

wa-chiss
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Brake drag could be frozen slides/pistons in the caliper, moisture in the fluid, seizing master cylinder piston.

pignosedslut
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Hey guys,

Do you have know any tricks to getting the pin out of the adjuster for the brake pedal? The side closest to the driver door is a flat head and the other I have to cut off is so inaccessible because of the steering column. How should I go about getting it off?

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centralcoaster33
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Lighting to see with, needle nose pliers, flat head screwdriver, maybe a pick... nothing really special other than being completely upside down, with feet up on the ceiling in the back seat and head down in the pedals.

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PapaSmurf2k3
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Yup. I've pulled the seat out before too just to help with it.
I'd do the master and the booster, then try and bleed everything (hell, maybe the seal in the master was so shot it wouldn't pressurize enough to bleed). If that doesn't work, dig into the calipers... if that doesn't work, you've gotta trace it back through the lines, or just pull the lines off the calipers one by one and then hit the brakes to clear whatever blockage may be in a line. That's pretty rare though.

pignosedslut
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I bled the rears and they bled pretty well then I had to go buy new bleeder screws because the last owner stripped them and when I came back the mc was pretty much dry and a lot of brake fluid under the driver left side. What do you guys think that is?

pignosedslut
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The rears bled well but the fronts just dribbled out. Is it a brake Line do you guys think or the caliper?

Could the bleeder screws be the wrong size? Would the hole for the bleeder screw in the front caliper drain that much fluid from just sitting?

The back brakes don't move at all after we bled them but i haven't started the car or anything. Could they just be locked from that?

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PapaSmurf2k3
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You'll have to follow where the leak is coming from. You shouldn't have to have the car running to bleed the brakes.
Did you replace the bleeders on the front calipers? Are you having someone pump the brakes while you look around for where the leak is? You should be able to find it pretty easily.

pignosedslut
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Leaks gone, lordco gave me the wrong bleeder screw. Bled it and the brakes were mint drove it around and the pedal went to the floor again while doing some skids. My pads were jumping around when I was driving my buddy told me. A little fluid is gone from the reservoir. Do you think I have a leak somewhere? It held fluid for a couple days while it sat but now the pedals soft again. Could my pads do that?

pignosedslut
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Should I just try to rebleed my brakes?

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PapaSmurf2k3
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Yeah the pedal should really never go to the floor. I'm not sure what you mean by "pads jumping around" either. They should be constrained within the braking system and really not have enough play to jump around. If you somehow lost a pad, then pressing the brakes hard would just extend that cylinder in the caliper (because it has nothing to push on), and the pedal would go to the floor. You should inspect everything again, make sure everything is present and tight, and that you didn't blow a line or create another leak somewhere.

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centralcoaster33
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Yeah, pads shouldn't be able to break free from their slot in the caliper unless they are worn down to the metal (I've done this) or where the wrong pads to install in the first place (pretty obvious during install), or the caliper wasn't assembled back correctly to the bracket (possibly just overlooked something).

pignosedslut
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Only one side is shaking so I'll take off the caliper and see what's going on there.

I'm also going to try and rebleed all four sides and check the bleeder screws if I fully tightened them after bleeding. I'll check for leaks while I'm rebleeding them. I still have a brake pedal but it's super soft and not safe at all.

pignosedslut
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I have hardcore brake drag in both rears but they bleed. Not sure what it could be. I could have had hardcore brake drag in the rear when I was doing a donut so it could have fried something. What do you guys think?

I'm gonna take off the calipers and clean them out, see if I can see anything. Also gonna check for leaks tomorrow too. I'll let you guys know.

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PapaSmurf2k3
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Yeah you can have brake drag and still bleed just fine. If the caliper is sticky it can happen. You might be able to push it back and forth with a clamp and the pedal to free it up. Might need new pads after that though.

pignosedslut
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I bought used calipers off my buddy and he said they weren't seized. I'm basically bending a wrench trying to push them in. Do you guys have any tips on getting the piston back in? Did he rip me off?

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PapaSmurf2k3
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IIRC, the rear calipers have to be turned in. They make a brake caliper turn in tool that you can rent from advance and autozone for free.


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