flatlander937
Member
- :
- '11 Mazda2 Sport
And noticed it has a cross split system?
The left rear and right front are on one circuit, and the right rear and left front are on another circuit.
If you have someone holding pressure on the pedal, you crack the left front bleeder, go around the car and spin all the rotors/drums... you'll find that the left front spins along with the right rear... I was not expecting to find this being a disc/drum setup(I guess because most imports use 4 wheel discs whenever I find a cross split system).
What I DID find odd is that if you try the same thing, but instead you crack one of the rear bleeders, I was able to freely spin both rears, and the opposite front... I'm wondering if there is some sort of built in residual valves into the ABS module, and with a pressure imbalance from left to right in the rear circuits, maybe it bypasses the opposite rear to prevent drum lock up?
After bleeding its got a nice damn pedal.
If you don't know what a cross split system is, or why you're wrong to bleed RR, LR, RF, LF then read this, a Mazda3 brake system is also cross split and I wrote this up a while back when I had my 3:
http://www.mazdas247.com/forum/show...S-How-you-REALLY-are-supposed-to-bleed-brakes
You should be bleeding RR, LF, LR, RF in that order to do it correctly.
I made that exact same post on another Mazda3 Forum and there was a pretty good discussion about it if you care to read more.
The left rear and right front are on one circuit, and the right rear and left front are on another circuit.
If you have someone holding pressure on the pedal, you crack the left front bleeder, go around the car and spin all the rotors/drums... you'll find that the left front spins along with the right rear... I was not expecting to find this being a disc/drum setup(I guess because most imports use 4 wheel discs whenever I find a cross split system).
What I DID find odd is that if you try the same thing, but instead you crack one of the rear bleeders, I was able to freely spin both rears, and the opposite front... I'm wondering if there is some sort of built in residual valves into the ABS module, and with a pressure imbalance from left to right in the rear circuits, maybe it bypasses the opposite rear to prevent drum lock up?
After bleeding its got a nice damn pedal.
If you don't know what a cross split system is, or why you're wrong to bleed RR, LR, RF, LF then read this, a Mazda3 brake system is also cross split and I wrote this up a while back when I had my 3:
http://www.mazdas247.com/forum/show...S-How-you-REALLY-are-supposed-to-bleed-brakes
I'm sure you have heard when bleeding brakes... you "start at the wheel furthest away and work closer to the master cylinder." This does not apply to the Mazda 3... it has a diagonally split brake hydraulic system... not a front/rear split like cars of yester-year and most trucks/SUVs.
The left rear and right front circuits are on the same port in the MC... and the right rear and left front circuits share the same port.
The benefit to this is that you will only lose 50% of your braking ability should one circuit start leaking. In a FWD car with a front/rear split, if you lost the front then you would lose about 70+% of your braking ability... not to mention locking up rear brakes would potentially spin you in a hurry, making the situation even worse.
The only reason that the old "start with the wheel furthest from the MC" BS was started was because back in the day cars only had ONE type of brake hydraulic circuit... the fronts were on their own circuit, and the rears were on their own circuit. So of course the rears are the furthest away... so going by that logic you bleed the rear circuit before the fronts... which is exactly how you're supposed to do it on a front/rear split system.
When you bleed the brakes in the "old" and wrong method(on a diagonally split system)... you bleed the right rear just fine... but when you go to the left rear next, you are starting a new circuit entirely... so every time you pump the pedal to bleed the left rear, you are sloshing brake fluid in the RR-LF circuit back and forth, adding a zillion bubbles of air because the new fluid you JUST put in there is getting aerated because it's not going out in one direction.
Also I constantly see people struggle with bleeding brakes and nearly EVERYBODY completely screws it up and ends up with only an "acceptable" pedal when done... but when done properly it is so much better.
The proper way to bleed brakes is to do this(for each wheel... in the correct order... discussed below) if you have a helper available:
1) Have helper stand on brake pedal
2) Crack bleeder screw. (Your helper will/should feel the pedal go to the floor... make sure they do not let up until step 4!) Use a clear hose to watch bubbles leave the system and pay attention to the color of the fluid.
3) Close bleeder screw when flow stops
4) Have helper SLOWLY let pedal up
HERE IS WHERE EVERYBODY COMPLETELY SCREWS IT UP!!! IMPORTANT: DO NOT under ANY circumstances let your helper "pump up the brake pedal." All they are doing is aerating the fluid and introducing more air into the system that you just started bleeding. It is a LOT easier to get out one large air bubble than it is to get 10,000 little micro-bubbles out of the system. The smaller the air bubbles, the more likely they are to stick to the walls of the inside of the tubing... letting fluid go around the air defeating the purpose of bleeding.
5) Have helper step on pedal again... note that it will feel soft and feel like crap, etc etc. Again... do NOT pump the pedal until the VERY VERY end! Fluid WILL come out when the bleeder is cracked! Just the pedal will not feel very responsive until the END.
6) Crack bleeder screw again and watch fluid leave the hose again. You can even listen for air bubbles and know if you're in a not too loud environment
7) Close bleeder when flow stops
8) Have helper slowly let pedal up again
Then you repeat this until the wheel you're bleeding is good, then go to the next wheel. BE SURE TO CHECK THE MASTER CYLINDER RESERVOIR CONSTANTLY TO ENSURE YOU DO NOT RUN IT DRY! GETTING AIR OUT OF THE SYSTEM WHEN THE M/C INGESTS AIR IS CONSIDERABLY MORE TIME CONSUMING. I generally top off the M/C at the start of each wheel, and check/top off about every 4-5 "pumps" with the bleeder open. Start out checking a bit more often to get a grasp on how quickly the fluid is displaced to minimize the risk of putting air into your system!!!
AGAIN... DO NOT "PUMP PUMP PUMP PUMP PUMP" to make the pedal "feel" hard until all 4 wheels are bled and you are done. It doesn't matter what the pedal feels like while bleeding, the idea is to only make the fluid move in ONE direction... that is towards the calipers and out of the bleeder. By pumping it, you slosh it back and forth and intermix good fluid with bad, and more importantly(and stupidly) fluid with air.
I guarantee you will not get a better feeling pedal by doing it any other way manually.
You should be bleeding RR, LF, LR, RF in that order to do it correctly.
I made that exact same post on another Mazda3 Forum and there was a pretty good discussion about it if you care to read more.