I have been trying to get my brakes bled for the past week now. I first thought it was the master cylinder. The brakes just wont get hard. I replaced the master cylinder, thats not it! The pedal will go to the floor when I bleed the rear brakes and will sometimes act like there is resistance half way down while bleeding but then will go to the floor with no resistance. When I bleed the front the pedal wont go all the way to the floor. The system will feel like it is getting pressure but when I turn the car on the pedal is spongy as hell, allmost like there is a big leak, but there isnt. My question is can it be the proportioning valve, thats the only other think i can think of. I tried to bleed it when it was hooked up to the new master cylinder and fluid only came out of one of the top holes. Can someone please help!!!!!! If it is the proportioning valve, where can i get one besides mazda.

 

Explain exactly how you are bleeding the brakes.

 

something your doing is not right...bleeding brakes have never taken me longer than 15 minutes...I always get someone to help me

 

I have bled the brakes plenty of times myself, and im not doing it any different this time. I just got done with the 5 lug conversion so i have the 4 pot calipers in the front. I am starting with the passenger rear. then the driver rear then pass front and finally the driver front. The thing is I dont think there is any air in the system. Ive bled it so many times, there cant be! The thing thats weird is when i am bleeding the rear the pedal feels totally different from the front. It will go half way down with some resistance and then the second half it will fall to the floor. the front feel really spongy and the pedal will fall to the floor with no resistance and sometimes wont go all the way down, it will stop 3/4 of the way. This is really weird. I cant figure it out and i only have a few more days till seven stock. I dont think it is the proportioning valve because it is a closed system and pressure would still build up and the pedal would get stiff right????

 

One huge thing with bleeding brakes that many forget to do is to pump the brakes up several times before each time you purge the caliper. This gets ALL of the air out of the system.

To me your description sounds like you still have air in the lines somewhere...

 

is there any way it could be the proportioning valve

 

Doubtful, sounds like you are drawing ait back in the system some where, or you have a leak.

 

there is no way the brake booster can go bad is there?

 

Yes, the diaphram can fail. Then the brake pedal is rock hard. This is not your problem, leave it alone.

If you are sure you have no external leaks, no air in the system, clean fluid coming out from all 4 bleeders, take the master cylinder back. If it's a used one, buy a new one.

 

I think you're bleeding the breakes wrong. If you don't have quick bleeds there is no way you can do it on your own...

 

I checked all the lines and connections last night and am going to bleed the whole system again tonight and see what happens. Do any of you have and thoughts on why when im bleeding the rear the pedal feels stiff for half way down then falls to the floor, and while im bleeded the front, the pedal doesnt want to go more than 3/4 of the way down .

Also what is the best way to make sure the master cylinder is bled since it is new?

 

bench bleed the master cylinder before installing it onto the booster. then start your bleeding process. you have the sequence correct. bleed each corner until new, clean fluid comes out of the caliper. if the proportioning valve werent working, you wouldnt get much fluid out of a certain side or caliper. have someone help you and make sure the two of you have good communication. make sure you hold the pedal tight to the floor between tightening the bleeder on the caliper. push the pedal slowly to the floor, dont rush it, you dont want to damage the master cylinder. post back after you bleed.

 

what are the step to bench bleeding the master cylinder

 

This sounds like you need to bench bleed the master cylinder. This is simple, and they sell kits if you need it. Run a plastic tube from the connections on the bottom of the master cylinder where the brake lines connect. Loop it back up to the master cylinder reservoir. Fill the reservoir with brake fluid. Pump the master cylinder until no bubbles come out. You can use the eraser end of a pencil to pump the plunger, and you'll need a vise or something to hold the master cylinder when you pump it.

 

I did this befor i installed the master cylinder. One thing i noticed is that fluid came out of the very front hole and the bottom, but no fluid came out of the rear hole - near the back of the master cylinder. is that a problem

 

Which master are you using, GSL-SE? Which proportioning valve, 2nd Gen?

 

i am using a master cylinder from a 84 with disc brakes in the rear, proportioning valve is for the same car - 84 with disc brakes.

do you need to bleed the master cylinder while the proportioning valve attached.

does the proportioning valve need to be bled

 

I had a similar issue with hard bleeding when I put FC 4 pots on my car. I went through 1/2 gallon of fluid before it got better. It got pretty good, but not perfect until I drove the car for a week and rebled. I have an '83 master, a 2nd gen proportioning valve, and GSL-SE rears. I am suspicious that it was air trapped in the proportioning valve.

 

I took the master cylinder of today and bled it again. Then I put it on the car with the proportioning valve hooked up. It seem to have allot of air in the proportioning valve, But still the pedal wont get hard. I think i am going to take it to a mazda shop and have them look at it.

 

thats weird.... are you getting celan fluid from all four calipers?

 

im getting clean fluid from all the calipers! I dont know what it is, every once in a while i will get a bubble comming up from the master cylinder but a have bled it several times.

 

The brake pedal has been only going half way down when i bleed the brakes. When I loosen one of the lines on the proportioning valve, the one closest to the master cylinder the pedal will then go all the way to the floor. does this sound like the proportioning valve may be bad.

 

Trace out you brake lines, the ppv only balances the right front with the rears, the left front is on it's own. The ppv can be taken apart and cleaned/checked.

 

How long did you have your system dry during the caliper swap?

 

I had the sysytm dry for about a week. I have just spent the last three hours re bleeding the master cylinder and proportioning valve and then the rest of the brakes, and still am having the same problem.

Whats weird is when i bleed the rear pass side the pedal will go all the way to the floor, but when i bleed the driver rear and the two front, the brake pedal will only go half way down and wont go any further. When I bleed the pass rear the brake pedal will go half way down, i will feel kinda a pop and then it will go down the rest of the way. I have no clue anymore what the hell this might be. I dont know what to do anymore.