petros_rx7

From first time who I bought my fd I have problem with my brakes.
The problem is that the first time who I pump the pedal is soft and going down to floor and I have poor brakes.If I pump second time quick then is hard and I have good brakes.
For this reason I have change brake master cylinder with brand new oem mazda, front rotors with brembo , fix rear rotors ,new brake pads ferrodo ,rebuild all the calipers with oem mazda rebuild kit, change brake fluid, and finaly I have replace the 4 pipes with goodrich.
After installing all this stuff and after 2 brake bleedings I have exactly the same problem.
I think that happend because the pistons of front calipers return to initial possition after about 5-10 sec.So it loose the contact with brake pads.Thats why with first pump the pistons cover the gap and make contact with pads and with the second pump I have real brakes.

I have search and found this:

https://www.rx7club.com/showthread.p...t=abs+bleeding

and some other threads but I can not found answer to my problem.

BlueTII

Check the 1-way valve in the rubber hose going to the brake booster. Mazda had a recall on this part. If it is clogged or allowing air to pass in both directions it will cause problems.

It could also be the ABS pump.

petros_rx7

I have check the 1-way valve in the rubber hose and is ok.My car have this recall done.
I also believe that maybe is abs issue.

zinx

iTrader: (3)

My car does this as well, and from link you posted it sounds like a lot of FDs do this. It is really annoying so if anyone has a definitive fix, i would love to hear it.

petros_rx7

Any idea any help?

DaveW

OK.

A question: If all FD's have this problem, but mine doesn't (completely stock brake system including the original brake pads (not just type, but the ones that came with the car, and I'm at 55K miles), what am I not understanding?

The only time I have ever had low pedal was after a couple of track days when the pads had worn tapered, and remachining them flat fixed that.

As everyone has stated, reasons for low pedal are:
- something compressible in the brake lines (air, old type silicone fluid, etc.)
- excessive flexing in the system (brake hoses, calipers, pads themselves...)
- too much space to take up (pad knock-back, caliper piston seals too sticky and retracting the pistons too much, pad taper wear, etc.)
- too high mechanical advantage requiring too much pedal movement to deal with the above

I have solved many brake problems in my and other people's cars and racecars. There is always a solution - it may be a compromise giving high pedal effort, for instance, but there (in my experience) is always a solution. The fact that this FD problem has stumped so many smart and experienced people, but NOT EVERYONE has it, is baffling to me.

So what is the commonly-occurring problem that is not present on absolutely every FD? We have to be overlooking something!

Is it related to build date? Was there some change that affects this?

Milwgearhead

I have this problem on mine also, and a friend of mine had it on his 93 as well. From what I have heard in the past, this is just the way they are. I've learned to live with it. Maybe this is more common in 93's rather than 94 or 95?

pincusa

iTrader: (1)

I have a 93 that had the same problems after I replaced the soft hoses. Bleed the brakes over and over, but still no change. Then I used a power bleeder... all the air is gone now along with the problem.
All I can tell you is that my problem was air trapped somewhere in all those brake lines.
Hope this helps

Andrew.

iTrader: (4)

That's what I was about to say Try pressure bleeding it!

EFS.O

Ok,here is my story:I have new pads,new rotors,stainless lines,new brake pump,99 spec power booster,speedbleeders,and ATE blue racing fluid.I have bleed the brakes 4-5 times in a row.I was extremely happy with the results,until i drove an Fd with 19000 something miles and everything untouched(OEM pads,rotors etc).I am telling you guys,there was a big difference.The 19000 miles FD has instant pedal response.No pad knockback,no double brake NOTHING.The brakes work flawlessly...I am very confused.....

DaveW

This reinforces my earlier post (#6). My brakes seem to me to work properly - no excessive travel, great response, excellent stopping ability)

Something has apparently changed due to replacing components. There must be:

1) more flex in something that was replaced than was originally there with the OE components
2) replacing pads, brake lines, etc., has caused there to be more slack in the system (the pads themselves, or the effect of pushing the pistons back with used seals, sticking slide pins in the rear brakes, etc.)
3) no one has been able to bleed the system properly (very unlikely - if I could do it properly, this is not rocket science).

Dave

petros_rx7

How is possible to have air in my brake system ?I have change the brake fluid with new one atem blue racing and bleed the system until will see the blue fluid come out from calipers.
It is possible to have trap air in abs system?
I dont think that is pad issue or on stainless lines because many fd owners use the same and have no problem with this parts.
By the way I have allready buy from ebay power bleeding system and I will try it, but I am afraid that the problem is other and not the air.
Can be the brake booster? need adjust?
Or abs proportioning valve?

DaveW

I have bled my system many times when replacing the brake fluid, so that is not very difficult, even without a power bleeder. I think the problem must be something other than air in the system - as DamonB says, not everyone would be having bleeding problems.

Dave

RXcetera

Add me to the list of people who has had (and still has) this extremely annoying problem. I've discussed it with quite a few people on here but we've never firgured it out. I've replaced every component on my system apart from the booster and abs unit but nothing has worked. I've also bled the system multiple times in the past 5 years with no luck. Of course, I've tried friends FD's and none of them had the problem .

I cant help but think that there's air trapped somewhere in the system that cant be removed with regular bleeding. The initial push of the pedal isnt just long, braking power is also significantly down. Once you get the 2nd tap in (as I'm sure a lot of us have gotten used to doing) braking force greatly increases (basicaly I'm getting more braking force with the same or even less amount of pedal pressure). Some abs units have bleed screws... FD's dont and maybe that's a problem.

The only other possibility I can see might be the damper valves used to dampen out ABS pulsations. Basically they are inline valves that allow 100% free flow one way and restrict the return of fluid back to the master cylinder to reduce ABS kickback. If one of these valves failed in the closed position (restricting), maybe it would cause our problem. Anyone have some spares they could try out?

RXcetera

Just read the link to the thread posted earlier about the booster argument. Can someone try disconecting vacuum to the booster and (slowly) driving around to see if the problem is still there? I would try but my car is stored for the winter.

petros_rx7

When you replace the brake booster and abs unit you dont see any difference?better or worse?
You replace all the abs system with solenoids or some parts only?
It is hard to believe that all the fd owners who have this problem can not bleed the system properly or all we have damage abs unit or abs solenoids.
I think that is just a adjustment propably on brake booster.
If read the chapter P on service manual Mazda use a special tool to adjust the brake booster piston.
If that piston didnt push correct the master cyclinder then the master cylinder can not press proper the brake fuid so the first pump is on air.But with second pump ,because brake system have allready some pressure,the brake works.
I will try to adjust my brake booster with EFS.O and post reply soon.
Have any one any tip how to do that properly?

RXcetera

I replaced every part except the booster and abs.

Maybe it's air that cant be bled by using the typical bleeding procedure. A few people have posted that they cured their problem by power bleeding.

When I changed my master cylinder, I made sure the booster rod was in contact with the pedal rod at all times. While bench bleeding the master (while it was under the hood) I could see that even the smallest pedal application was displacing fluid. I cant see how it could be the booster...

petros_rx7

If the booster is always in contact with master cylinder then it can not be the booster.
So propably trapped air on abs or solenoids.....

dradon03

iTrader: (2)

I am curious about this of all the FD's I have known I have never heard of this problem (Maybe 10-12 FDs)

petros_rx7

I know 10-12 fd owners and only my fd have this problem it is not a common problem but many owners live with that as I can see.

I have found this while searching the web.
http://www.teamscr.com/brakes-antilock.html

Maybe we have to do the same.
But how to make the abs work on not running car?

airborne

I have the same problem. I've got SS lines up front, rebuilt my front calipers, new master cylinder, and played with the pedal height and travel. Still a little bit of initial mush. I've bled the system normally, i've had a shop do it, and I bought and used a motive power bleeder. no help.

I don't think that procedure above will work, though it sounds like a good theory.

"replace Step #2 above with "go driving and slam on the brakes a few times to make the ABS work" "

Who *hasn't* used their ABS since they had the problem? I forget, what is the procedure the shop manual gives?

petros_rx7

I will try to enable the abs motor and the 3 solenoids of abs while I bleed the system.
I see the wiring schematic and is easy to activate it.

airborne

Please write what you find! Obviously it could help a bunch of people.

good luck

DaveW

Any progress? This is quite interesting.

Dave

Busted7

Im having a problem but it may not be related. the brakes have not been the best for 4 years. Its a little better when you double pump but not good. I have removed the abs and installed proportioning valve bled the lines and have the same result. But what i have found is the rear calipers are not adjusting and im probley only getting about 30 percent rear brakes. There was even polishing of the rotors, no wear pattern. New calipers and lines are on the way. The car sat for 5 years and could have damaged the brake calipers. I will let you know.