Hi,

This is the result of several days of struggling with what I expected to be a 4hr job on my daughter's 2008 mazda 3.

I bought a new replacement master cylinder from a local auto parts store and installed it. The brakes do not always fully disengage causing brake drag. It drove fine for a block or two until I noticed it didn't idle forward by itself any more.

During one step of my troubleshooting, I loosened the bolts on the master cylinder, the brakes freed and the car rocked backward till the transmission (in park) stopped it. I noted another web page where someone said they added washers or something to make it work. This doesn't seem like the best approach to me.

Question: Does the brake booster on the mazda have anything that can be adjusted in the linkage between the M.Cylinder and the brake booster? Other vehicles seem to have a way to adjust the rod on the brake booster, but I haven't see anything like that for the mazda 3.

Any suggestions?

Thank you.

 

Did your replacement master cylinder come with its own pushrod? or did you reuse the old/original pushrod? or does it not have a removable pushrod?


The fork that connects from the booster to the brake pedal, it may ( TBC) have a lock nut, which if loosened, & the fork removed from the pedal may be able to unwind/ wind up to adjust the pushrod / fork length.

Below is a diagram from a 323 which shows my description.

 

HI Grim_Reaper,

Thanks so much for replying.

The master cylinder (MC) did not come with a pushrod for the Brake booster(BB). For the Mazda 3 it appears to be a fixed position with no adjustments, nor could I find any adjustments on on the pushrod of the BB like some of the older systems in different vehicles. I even found a tool that someone sells for measuring and adjusting the rod's position, but since I don't have an adjustment, it doesn't seem applicable.

I did think of playing with the fork on the cabin side, but it bothered me that I had to adjust it. I also put back the original one (it worked OK for the most part) and the brake drag problem went away. I then went to the dealer to find an OEM MC and they said wow, it's rare for them to go bad, so rare that they would have to order one and it wouldn't be in for a couple months ad was double the cost! .

I went back to my local auto parts store and ordered a re-manufactured one that came in later that day (while waiting your response came in...). I installed it and it seems to work fine. My best guess is that the 3rd party replacement MC is slightly longer or different in some way that it isn't an exact match and was causing the problem. The remanufactured one was an original equipment MC that was rebuilt, so it should have the same dimensions as the original.

It's also possible that the first one I bought was "a lemon". Anyway, that's my story.

I do seem to have a case where go around 10mile per hour and lightly brake, that the pedal seems to gently drop. It always keeps the brakes engaged, and hard stops work, so it's not like the MC is leaking internally. Someone said I just need to bleed the brakes thoroughly, so I'm looking for confirmation on that. Your thoughts?

Thanks again for the reply and diagram, I appreciate it.

 

@jbk Were you able to figure out how to adjust the brake booster pin? I'm currently in a similar situation.

Did you try adjusting the nut at the fork?

 

What do you mean you added the old one back and the break drag went away? I am having the same break drag problem

 

did you ever fix the problem? I having the same issue.thx

 

did you ever resolve the problem ? did bleeding the brakes again work ? I am having the same issue?

 

I replaced the master cylinder and brake booster and now have same issue with the front brakes locking up