Soft brake pedal

[Gobbracing]

I hope some of you can help me with this.

I bleed my lines and the pedal becomes firm again, but the second I brake hard a few times, it becomes soft and lower. My fluid level does not go down, I have new front lines, front calipers, and master cylinder. I use DOT 3 Ford specific oil right now for its higher boiling point.

Since I autocross a lot competitively I have Grand Sport 3 pads on the front and another aggressive pad on the back that I don't remember the brand.

I might be switching back to racing brake oil over the week-end (Motul RBF600 or SuperBlue) depending on the suggestions I'll get.

I hope my ABS module is not dying on me.

 

[Mazda_Tech]

make sure you are getting all the air out, you may not be, bleed the brakes again do it in this order RR,LR,RF,LF. Also make sure you are closing all the bleeders tight, and check for fluid leaks at the calipers and the lines that you replaced.

 

[Gobbracing]

I'll do. Thanks!

 

[Gobbracing]

Well my mechanic and I bled the brake last night on his lift (that goes so much better) and found a couple of small bubbles in the right front line.
Did a dozen heavy braking test from 35 mph and the problem did not come back. Just to say what a few bubbles in a brake line can cause.

Well, last autocross this week-end in Ottawa. Hope I can maintain my 4th in the ST championship or pick up a spot.

 

[orng1]

Yeah that's it air can be compresed, well good luck to you on your event.

 

[Ryoga28]

Good timing, I just got the same problem. I bled my brakes last night using speedbleeders and the pedal was firm last night. This morning, it's soft again. This is the second time this has occured to me. Should I just bleed the system again?

Thanks

 

[Gobbracing]

The problem stayed when I bled my brakes by gravity.
The best way I find is to have a friend pumping and holding the pedal while you take care on opening-closing the bleeders one at a time in the exact order as Mazda_Tech said.

 

[ChopstickHero]

The problem stayed when I bled my brakes by gravity.
The best way I find is to have a friend pumping and holding the pedal while you take care on opening-closing the bleeders one at a time in the exact order as Mazda_Tech said.

yep, that's the best way. or get Speedbleeders. I hear those work very well.

 

[orng1]

It can't hurt to bleed it again, if anything you'll be out anoter $5 for a bottle of fluid. Just ask a friend to help you out.

 

[livelyjay]

I've always had a friend help me with bleeding the brakes. Now I have my wife help me and she enjoys it because it makes her feel like she's actually working on the car.

 

[Gobbracing]

Well my autocross his done and I got a good score with my mostly stock MSP in Street Touring.

Now just one thing. My pedal went low and not as soft as before. After talking with a guy that had a similar problem on is Mazda3, he suggested replacing the vaccum hose (which contains a valve) that goes from the engine to the brake booster. He had a similar problem and that was the part his dealer changed to fix the problem. What do you guys think?
I might change it just as a precaution since I have over 65K miles (110K km) with a lot of lapping and autocross.

 

[evolv]

Yeah that's it air can be compresed, well good luck to you on your event.

and so can liquid... A drop of oil 10,000 feet down will expand 7 times its size at the surface.

 

[MP3Performance]

Hey Gobb, did you try replacing the vaccum hose with that valve? Does anyone else know if that could be the cause of the problem? My brake pedal is kinda soft but only under hard braking. I replaced my brake pads a couple weeks ago and one rear caliper. I didnt notice it at first, since I didnt brake hard, but after a couple hard stops it seems the brakes are a bit mushier then before. I only bleed the line from the caliper that was replaced. I will probably try bleeding all the brakes tomarow.

Dont get me wrong, the brakes do stop good (I have stoptech slotted rotors in the front, stock in the rear, and hawk pads all around). But the first time mashed the brakes the pedal caught me off guard. I do have an MP3, so I dont have abs, and the brakes are a bit different, but I dont think that matters.

 

[orng1]

and so can liquid... A drop of oil 10,000 feet down will expand 7 times its size at the surface.

LOL "More easily compresed" then.

 

[Gobbracing]

I haven't changed the hose yet since it's back to normal driving for a few months. But for sure I'm gonna change it because of the mileage on my MSP.
I should do it before the end of the month.