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Discussion Starter #1
I replaced the front pads on my girl's 2013 3i yesterday, and didn't have any issues. On each side, I jacked it up, removed the tire, removed the caliper, removed the old pads, pushed the piston in with a big C clamp, put the new pads on and reattached the caliper.

After taking it for a test run, it was obvious that the brake pedal was very soft. I had to push it almost to the floor before it would begin to stop. If I pumped the brakes a few times while stopping (to build pressure) it felt normal. I figured I had to bleed the brakes.

I bled the front, one at a time, the way I always have in the past (on other cars .. this is the first brake job on the 3). She sat in the drivers seat, pumped the pedal a few times then held it down, I loosened the bleeder screw, pedal went to the floor, tighten the bleeder screw, and then release pedal. We did this 4x on each side. I added a bit of brake fluid to the reservoir after each side was done. The brake pedal is still soft.

Question: Do I need to bleed the rear brakes as well? I read somewhere that the front & rear brakes share the same fluid "circuit" (not sure what the term is).
 

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Demon Spawn
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yes, you must bleed the entire system when doing any brake work that would require bleeding, or you feel it needs bleeding, as air can get into any part and usually travels down to the caliper(s) or gets stuck in the ABS module (which can require a scantool to bleed right and air getting stuck there is rare but happens) on the 3 the brake system is not split front to back but rather diagonally so the front right and left rear are on the same side of the master cylinder and the front left and rear right are on the same side. this setup helps in the event of a failure that halts one "system or side of the brakes, this way you still have roughly 50% of your brakes in and given situation instead of if fronts and rears separated by front and rear and you lose the front system you only have 30% or so. but anyways I digress to bleed the system correctly start at the rear and then do the front diagonal to you then the other rear and front diagonal to it. its odd but that's how it works on these cars. I had a similar issue with soft pedal, but mine would also jerk back when I hit the brakes making me feel as if a caliper had stuck, and low and behold one did, as well as the seal letting air past the piston (so small a hole in it brake fluid would barely come out if we compressed the piston very hard but that's all) so I had a mushy pedal and a caliper issue, well when changing calipers you usually lose fluid, not so much when I did mine, we where able to hold back most of the fluid, maybe a few drops on each caliper came out (changed both rears as you always change calipers as a set per axle if one fails, passenger was bad one)

anyways after slapping it all together with new pads and rotors to boot I had not lost any fluid in the reservoir, so I pump the pedal, still feel soft go for a drive still a little soft so I bleed the system back to front and low and behold a ton of air comes out the front right and rear left a little on the others, well I go and drive again after refilling thinking all the air is out as it appeared to be, pedal still kinda soft. so I remembered on the 08 3 I had (this is a 2011 I am talking about fixing) the forum here and another one both stated to bleed diagonally not side to side, so I did that and low and behold a lot more air comes out and I used almost 32oz of brake fluid bleeding it (all the fluid in the car is new DOT4 now so that's a plus) I could tell right when I started the car up, the pedal was rock hard and felt awesome best brake pedal feel I have ever had in a car! I go and drive and it feels amazing it stops right as I hit the pedal no mushiness no "when are my brakes going to work" thought for a half second before they grab they start grabbing the instant I push the pedal and hold stronger then ever.

so I would recommend bleeding diagonally as I stated further up in the post and see if it gets better. and use DOT 4 fluid as it has a higher dry (no water in it) and wet (water has gotten in) boiling point (brake fluid and water don't mix well together) then the factory and store bought DOT 3 as the DOT4 specs a higher temp fluid that can take more abuse DOT3 and DOT4 are fully compatible with each other so you can mix as much as you want of them. DOT4 will make the fluid last a little longer and take more abuse though. DO NOT I REPEAT DO NOT use DOT5 brake fluid as it has silicone in it and that will chew up your brake system if you can find it DOT 5.1 is supposed to be compatible with DOT3 and 4 and can be substituted, though I have yet to find any locally and I am not paying the price for it many places want, as 5.1 is pretty much racing brake fluid and would just be overkill in many street cars let alone a Mazda 3 with a 4 cylinder motor so I would suggest a good DOT 4 fluid such as Valvoline (theirs will be labeled DOT 3 & 4 at places like autozone and the like but it meets the same specs as regular DOT 4 they just put 3 &4 for people that don't know they are compatible I used this fluid in many of my cars as it is readily available at many stores and I know im going to get the same quality each time) or Prestone or even Lucas DOT 4 fluids
 

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Discussion Starter #3
Thanks for the reply .. i'll try bleeding the rear and front tonight (doing RR, then LF, then LR, and RF). Are the bleed screws easy to get to on the rear? I can easily get to the front without jacking the car up, just by turning the wheel fully to one side.
 

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Demon Spawn
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the rears are a little bit of a pain without jacking since you cannot turn them but it can be done without jacking, I would say jack it if you have one that works quick as it will make things quicker and easier.
 

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Thanks for the reply .. i'll try bleeding the rear and front tonight (doing RR, then LF, then LR, and RF). Are the bleed screws easy to get to on the rear? I can easily get to the front without jacking the car up, just by turning the wheel fully to one side.
Tell us what happens...I have a mushy pedal on my '14 also...
 

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Demon Spawn
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question for you guys. are you letting the pads wear down almost to metal before replacing them? this could be the source of your issue if all you have done is change pads/rotors there should be no air in the system and no need to bleed, however if you let pads wear almost all the way to the metal backing or all the way to it before servicing this could be your issue, as letting them wear too low for extended periods over extends the caliper piston to apply brake force when needed, then when it goes back in there is not enough fluid in the system to keep the air in the reservoir out (yes there is always an air pocket in your reservoir) this balances the pressure, and that's why there is a max line lower then the top, so you have this air pocket. well when you over extend that caliper piston it has to come back to somewhere and it will typically come back all the way in (unless this is done too much then the caliper breaks but that's another story) and since the system is closed it fills the gap with something and this where you get the air sucked in as it sucks down more and more fluid to the bottoms of the system during use (calipers) it has less and less to push back as your pads wear when the pistons retract as the fluid gets below the min line you then get little bits of air pulled in with the fluid as it has to fill the gap and air is right there so it sucks air in as it does not have enough fluid to fill the void, then you get the spongy, soft pedal and lack of braking power.

I had this issue on my '11 GT, when I bought it I knew it needed pads (61k miles, factory pads where shot, and they where factory, I know I changed them myself)well 61k is a loooooooong time on one set of brake pads 30-40k is typical wear life of a good pad (replacement before it wears to metal backing or close to) well when I test drove it all was good. Changed the pads and rotors 3 days later at all 4 wheels and pedal goes soft, so I check my work, everything is in right and tight cant be that. So I decided to check the fluid levels again, well once you get to minimum level on the fluid(with no leaks) its time to change pads just as when you put new ones on it should come back to max. So I check my fluid level only a hair above where it was when I started (right above min) so I knew right then bleeding would be needed tried the traditional front to back still had a soft pedal then I remembered my 08 needed to be bled cross wheel as the system is tied opposite front to opposite back wheel so I tried that and pedal got better, did it again, still softer then I would like but getting there, again and after the 3rd time the pedal got firm before I even added fluid (while bleeding) I knew all the air was gone, closed er up, topped off the fluid 1 more time and went for a ride, pedal is nice and firm car stops on a half dime now.

so just a word of warning keep an eye on your pads, the absolute easiest way to do this is to make sure your fluid is at max when you change them and you have no leaks, then keep an eye on your brake fluid level when your checking other fluids if its getting to min you need pads and pads and rotors are cheap insurance against brake failure, so I recommend checking all 4 wheels when your doing any brake work im so anal I even change both sets of pads and rotors(rotors are so cheap you might as well replace instead of turning and/or reusing) each time I do brakes just because I cannot stand having to do brakes once then 2 or so months later have to do it again for the other set, might as well get it all done at once. plus im anal and ocd about car upkeep so having all that done eases my mind for a little bit

another tid bit, DOT 3 and DOT 4 fluids are compatible with each other and can be mixed, however if your car calls for DOT 4 don't use DOT 3 as it has lower temp handling, but our cars call for DOT 3 so subbing in DOT 4 will get you a higher temp handling fluid that should last a little bit longer and DOT 4 fluid does not typically cost more then DOT 3 However do not use DOT 5 as DOT 5 is a silicone based fluid and will gel up in our system if mixed (not good, and will not mix with older DOT 3or DOT 4) if you want to even try to use it (way not needed in these cars) you will need to flush all the old brake fluids out of everything and I mean everything and they must be spotless so not worth the cost and labor of doing it, however if you can find DOT 5.1 (very hard to find in stores anywhere, even online its hard to get) it is compatible with DOT3 and DOT 4 but for the added cost and effort to find it DOT 4 will serve you fine, we are not running 300 laps at Watkins glen in 700hp cars just driving a 170ish hp 4 cylinder mazda around.
 
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