2004 to 2016 Mazda 3 Forum and Mazdaspeed 3 Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
17 Posts
Discussion Starter #1
hey guys
any of you changed the brake fluid on a BM/BN mazda 3 sp25 / 2.5L (more specifically 2017 year).?

I had a read of the workshop manual and it states after performing the air bleeding on the calipers, to go back to the rear pads and you have to screw/unscrew the brake piston a few times (using a special tool) to bleed more air out...

has anyone ever done this?
 

·
Registered
Joined
·
1,272 Posts
That sounds about right. It's a pretty easy task. Only issue is the ABS valve body. Bleeding the ABS requires a fairly high end diagnostic scanner that is able to put it into test mode. Without that you can't properly bleed the ABS.
What that means is that for DIY you will have to accept that the ABS will not be flushed out. This means that you have to bleed off a little at a time during your flush. Fluid level must be kept above low line in the reservoir to avoid introducing of air into the system that could make its way to the ABS.

Also do remember that our clutch fluid shares the same reservoir if you happen to drive stick.
 

·
Registered
Joined
·
522 Posts
Only issue is the ABS valve body. Bleeding the ABS requires a fairly high end diagnostic scanner that is able to put it into test mode. Without that you can't properly bleed the ABS.
What that means is that for DIY you will have to accept that the ABS will not be flushed out. This means that you have to bleed off a little at a time during your flush...
1) I'm not sure, but this fussing with the rear calipers may only apply to vehicles with manual parking brakes. With electric parking brakes I think you can put the latter into "mtce mode"... Not sure when the "3" went to an electric parking brake; and

2) can you please explain the comment re "bleeding off a little at a time during your flush"... Are you intimating that you can indeed get fluid to run through (and therefore flush) the ABS unit, though, slowly?
 

·
Registered
Joined
·
1,272 Posts
1) I'm not sure, but this fussing with the rear calipers may only apply to vehicles with manual parking brakes. With electric parking brakes I think you can put the latter into "mtce mode"... Not sure when the "3" went to an electric parking brake; and

2) can you please explain the comment re "bleeding off a little at a time during your flush"... Are you intimating that you can indeed get fluid to run through (and therefore flush) the ABS unit, though, slowly?
Maybe bad wording, should say to bleed a small amount at a time. The idea is to not lower the reservoir level too much as to risk air getting into the system. If it does, there's no way to know if it will end up in the ABS so you'd want to bleed it properly to be on the safe side.
 

·
Registered
Joined
·
964 Posts
I’ve bled my 2014 several times already.

Who cares about the ABS unit. The new fluid will eventually go thru it with use and you can flush the brakes again as the fluid gets dark in a year or two.

mine is manual so I flush the clutch cylinder as well. The clutch pedal feels so much better afterward and clutch engagement needs to be relearned slightly.

I always keep my fluid looking clear / golden which seems to take about 30k miles or so for the oil change intervals.
 

·
Registered
Joined
·
522 Posts
... meaning air seems to make its way into the clutch hydraulics. When you bleed it the "bite" point becomes higher in the clutch pedal travel... and the "fully disengaged" point rises too, thereby giving your synchro's an easier time of it and a longer life-expectancy.
 

·
Registered
Joined
·
1,272 Posts
Who cares about the ABS unit. The new fluid will eventually go thru it with use and you can flush the brakes again as the fluid gets dark in a year or two.
People who care about their safety systems working properly care about the ABS. I've heard the arguments. "I can pump the brakes better than the computer", etc. Until you can pump the brake pedal several hundred times a minute I'm calling BS on that one. This is why many of us like our ABS to work correctly.

If air gets introduced into the valve module, it doesn't go anywhere until the system is activated. This is a safety system which means you need it to work when it is called on to function. So in that instance, it might not work correctly or worse yet may send that air to the caliper and reduce brake power when you really need it.

The solution is simple. Keep the reservoir above the minimum line while bleeding. Something very simple and all risk is eliminated. Seems like a good trade off to me.
 

·
Registered
Joined
·
522 Posts
I would like possibly to get an interrogation device that will operate the ABS unit to bleed it / flush it. Expensive? Easy to find?
 

·
Registered
Joined
·
17 Posts
Discussion Starter #9 (Edited)
ok this is what it says in the 2014 service manual.
Im curious if im just replacing the brake fluid (and keeping it above the min mark). is that rear caliper step really necessary?
Ive bled/replaced fluid on plenty of vehicles using the 2 person method this is the first one I've come across where it asks you to do this extra rear caliper step.

277039



277042

277043
 

·
Registered
Joined
·
1,272 Posts
ok this is what it says in the 2014 service manual.
Im curious if im just replacing the brake fluid (and keeping it above the min mark). is that rear caliper step really necessary?
Ive bled/replaced fluid on plenty of vehicles using the 2 person method this is the first one I've come across where it asks you to do this extra rear caliper step.

View attachment 277039


View attachment 277042
View attachment 277043
i'm honestly not sure why it wants you do rotate the piston. necessary to move it, but if you're just changing fluid? not sure. anyone else have any ideas?

the idea of keeping level above the min mark is if the fluid falls below the reservoir you don't really know where the level is. the ABS unit is well above the brake calipers so there's no way of knowing if air has gotten in there. only way to be sure is to bleed it at that point. keeping above min level means you know there's no chance of air getting in there.

it is possible to partially bleed the ABS with the bleeder, but some of the fluid will remain trapped. personally, i wouldn't care much and i'd be happy to get what i can.

honestly i think brake fluid change is often unnecessary. changing any fluid based on colour doesn't mean it's still good or not. engine oil will darken over time as will transmission or brake fluid. doesn't necessarily mean it's gone bad. moisture is the item of concern with brake fluid. there are inexpensive testers available for this. on the other hand, if you really want to change it you're better off to change it too much than not often enough.

i'm currently sitting at 5 years and 160k kms and still don't need to flush it.
 

·
Registered
Joined
·
522 Posts
The darkening of the brake fluid is corrosion product of the metallic components in contact with the brake fluid. Through molecular diffusion - if any location within the system is i) corroding; and ii) is in contact with that same fluid - then ALL of the fluid will hold those corrosion products and will darken more-or-less uniformly. So, a change in fluid imbues the new fluid in contact with those vulnerable components with less moisture / less corrosivity. I am not sure darker fluid is otherwise impaired in its function as brake fluid. It is wise to change it though for reasons of preserving life expectancy of the componentry.

If you flush the system at 24 mo. intervals you may NEVER need a new caliper, clutch slave cyl., or new brake- or clutch master cyl. With this molecular diffusion phenomenon it may also help the ABS unit. BUT... the big caveat is to use the vacuum- or pressure method for bleeding / flushing.. not the two-person method!
 

·
Registered
Joined
·
522 Posts
i'm honestly not sure why it wants you do rotate the piston. necessary to move it, but if you're just changing fluid? not sure. anyone else have any ideas?
I believe it has to do with how the rear calipers operate the pistons when actuating the parking brake on the mechanical parking brake models. I think that this action eliminates any points where old fluid (and particularly any air in the system... which rises to a high spot) can accummulate. So in eliminating that high spot trapped area, you can effectively flush new fluid through the rear calipers using this step... and then you need to reverse this step to put the rear calipers back into "operational / normal" mode. Re the electronic parking brake models, you MAY have to put the rear brakes into "service" mode to accomplish the same. I'm not sure. I do know that svce mode IS required on those for pad changeouts.
 
1 - 12 of 12 Posts
Top