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Discussion Starter · #1 ·
A few months ago I was replaced front brakes and rotors and also replaced/flushed fluid. Shortly after the brake pedal lost its firmness. I have blead the system 3 times fully, (the last two included the master, just in case) I went through 2 large bottles and 1 small bottle of fluid.

The car stops but there is something not right. So i go to the dealer today hoping they can do a power bleed. They took it back to have their tech look at it and said the fluid is clear and that the symptoms point to the master cylinder. That it is bypassing and not holding pressure.

The car has 61K miles on it (2010). I'm a bit pi$$ed right now. Last thing I want to do in the middle of winter is replace the master and flush the system again.

Any one have any luck with a particular brand of master cylinder?
 

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Are you sure there isn't any recalls? My 98 is going in this week for a master cyclinder replacement under recall. I could have sworn when I was reading I saw recent ones.
 

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2002 BMW 325i, 2007 SS Trailblazer, 2012 Acura TSX Wagon
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Well, I'd be pissed as well but at least its a somewhat easy job.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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Sometimes stuff happens.

What happens sometimes is as the pistons of the master cylinder goes up and down, they develop a ridge inside the cylinder bore. This doesnt usually happen till higher mileage but it does happen lower. When someone goes to bleed or flush brakes, they may use the pump pedal method. When this method is used, you can over travel the cups in the cylinder and break through that lip of gunk. Sometimes what happens is that the cups in the master cylinder get damaged by breaking through this lip. This is what happened here.

Just curious, has the fluid been changed anytime before this?
 

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Discussion Starter · #6 ·
Fluid has not been changed to my knowledge, as I am the original owner. The car had 2** miles on it when purchased which was in Jan. 11, but the build date is in 09. I decided to change the fluid when I did front discs due to the age of the fluid which was coming up on 3 years.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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61K is a bit long between fluid changes, that might be the reason it failed. it is not unusual but a little light in the miles for this to happen.
 

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Hard to imagine such new vehicle having any issues. I'm not recommending it...but, i change brake fluid every 100,000 miles...maybe. i know, shame on me, like i said i'm not recommending or discussing it - just saying I doubt the fluid is the cause here. i never changed brake fluid in any subaru in the 1990's, just because I didn't know, i used to drive around with 200,000 mile fluid in them and i've never had an MC or caliper failure. now that i do change it sometimes...even with 100,000+ mile fluid in it, i've never noticed a difference. either way the brakes bite and lock right up.

i towed a 2,500 boat of all things with my 03 sedan last summer in 95 degree southern heat through the mountains and the brakes did great on the 160,000 mile vehicle which i've never changed brake fluid in.

again - not recommending it but my experience is that brake fluid doesn't break down or degrade quickly...if it did, as a rule, I'd surely have encountered far more problems. i'd imagine it's "nearly new" at 30,000 miles.
 

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I agree with grossgary, this failure was likely not due to the fluid being old.

To check that it is the master cylinder do the following: With car running, in drive, and with your foot on the brake, firmly but don't try to push it to the floor, do your best to hold your foot still. Now if the brake begins to push less and less against your foot don't push harder. If your master cylinder is bypassing eventually your car will begin to roll forward, though this may take a minute or two to happen. What you are trying to do is determine if the fluid compressed by the master cylinder is sneaking past the cylinder seals. If the car doesn't ever move then I would be reluctant to say your problem is a bypassing master cylinder.

I had this happen on an old Acura Integra. At stop lights I had to keep moving my foot down on the brake and at long lights I had to apply the parking brake and reset my foot. One thing you never mentioned is how familiar you are with vehicle maintenance and if you have flushed and bled a brake system before this. Please don't take this the wrong way if you are a well accomplished home mechanic.
 

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Discussion Starter · #10 ·
I am the original owner. I bought the car new (2XX mile...it was a demo) in Jan '11. Car build date is late is fall of '09 if I remember reading the sticker correctly. I changed the fluid when I changed front pads at around 55,000 miles.

I have been working on cars for years, but I may have missed something...who knows. I have tried the pump method (to the point the wife got annoyed with me) and gravity bleeding with no luck.

I wrote Subaru a couple hours ago, and also mentioned the recall. Who knows.
 

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Could simply be a Mastercylinder that had a flaw in it and the fluid change simply brought the flaw to the surface.
I would expect Subaru to at least share some of the cost.
 

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Doesn’t take much to bleed brakes, just did my Accord last year (every 3 yrs) and the fluid is clear after 6oz per corner = 1 (32oz) big bottle to bleed the car. But after bleeding 72oz (18oz x4) and your pedal is still sinking, MC most likely. Leaking seals, luck of the draw it seems here.<O:p</O:p
Shop cost, I’d say ~$250 independent mechanic. Your garage, ~$100 parts.<O:p</O:p
 

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Discussion Starter · #13 ·
Well, Subaru was no help, and wouldn't help so I am a not very happy.

Dealer wants $277 for a new one and a reman A1 Cardone runs 110 from the local auto parts. I will probably go that route.

Has any had any problems with Cardone stuff? It doesn't come with the reservoir or sensor, Im assuming it is pretty easy to transfer over? I have only done the old school 1 piece master cylinder on old cars.
 

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2005 OBW 2.5L, 1989 Subaru Justy, RIP Blu
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Its really easy. Hardest part is bleeding the system afterwards (easy just annoying)
 

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2016 Carbide Gray Limited with Moonroof, Nav, and Eyesight
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Power bleeding with the right equipment is much easier on the system and practically guarantees no bubbles and a firm pedal. When I changed fluid at 30,000 miles this was used and the cost was about $80 including fluid.
 

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Power bleeding with the right equipment is much easier on the system and practically guarantees no bubbles and a firm pedal. When I changed fluid at 30,000 miles this was used and the cost was about $80 including fluid.
What brand of Power bleeder do you have and is it a 1 man operation?
 

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Ive done the hand pump one, where i use that to start things then just let gravity keep it going. Surprsingly the only shop near me with a power bleeder is a Iffy Lube, all the others prefer the old fashioned method. They say it is quicker.
 

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What brand of Power bleeder do you have and is it a 1 man operation?
I know you weren't asking me... But I use a Motive power bleeder. I haven't used it on my Subaru yet, as I only have 33,000 miles, and it is only 1.5 years old. However, I have used it on VWs and Toyotas. It has worked very well. I also ended up getting their catch cups so that I can bleed more than one wheel at a time and not make a mess.

Also, I am a fan of the ATE Super brake fluid. You can get it in clear or blue, which makes it easy to see the fluid change.
 

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2016 Carbide Gray Limited with Moonroof, Nav, and Eyesight
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What brand of Power bleeder do you have and is it a 1 man operation?
It is a one man operation. I do not do enough work anymore to own one, (I use the vacuum pump style on my motorcycle). I had it done at the Subaru dealership, I believe they use a BG power bleeder. The complete removal of old fluid, any debris, and bubbles left a very good feel with the brake pedal, and inexpensive peace of mind.
 

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On two previous vehicles, I had the MC fail after a pad change. In both of those cases, I pressed the pistons back into the calipers and, thus, back into the MC. Now, when I press the pistons back into the bores, I loosen the bleed screw and let the fluid leak into a large pan. Using this method, I have never hurt a brake MC since. The back pressure must be pretty great to blow the internal seals of a MC.

Of course, I then have to bleed each caliper after the pad replacement.

Maybe this is what happened to you??
 
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