StarScreaM2k1

Ok so, this braking problem is really whacko and can’t seem to find a solution...So let me explain and give the background info.

It’s a 10thAE RX7 and I bought it in September last year (2004) it sat in the garage in winter up until now where the weather has gotten real nice (and I have enough money to insure it) and anyhow… when I got the car the brakes were fine, a bit mushy but only if u were really picky about it. So about a month ago my brake pedal went soft… like clutch like soft ( I can push it right to the floor) and it would not brake (like the brakes did not stop the car). So on Wednesday me and a few friends were working on it, and we bled the system (we first gravity bled it, then forcefully bled it (both a few times (about 3 or 4 times)) the pedal got a bit stiffer, but not by much @ all. And another key note is that THERE WAS NOT LEAK FOUND (we checked the regular locations), and also when we pressed on the brake there was a sound near the Master Cylinder (we couldn’t tell if it was the MC (master cylinder) itself or the Proportioning valve or brake booster) it made like a WOOSH sound like air being pushed out OR sucked in. So I went ahead and bought a NEW MC. We installed it, bled the system (both by gravity first, then by force and a few times (2-3 times)) and the pedal got a bit more firmer and pretty good to (but not as how its supposed to be, we can still push hard right to the floor). And even after the new MC, it still makes that WOOSHING sound. Once we turn the car on. Pedal firmness is all gone. However the car will stop… gradually but it will like it comes to a halt but slowly. Also on a hard brake one of the rear tires (I think it was right) will lock up. But the pedal is to the ground though. Like it’s barely braking, but that 1 tire locks…. So any ideas? Can it be the Master Again? (I doubt it since it is a BRAND NEW ONE and the same sound is being made), can it be the brake booster? Maybe the ABS unit (oh god I hope not!!) or maybe the proportioning valve? Please this issue is halting me from using the car! LOL so any help is welcomed. Maybe some Links or something I tried searching, but nothing is like this… THANKS!!!

ViperBart

iTrader: (3)

sounds like your pressure differential valve is off to one side... how did you do the bleeding of the brakes the last time you changed the MC?... did you bench-bleed the MC?

StarScreaM2k1

i dont think we did the bench bleed, how do u do it? and is itwith the MC on or off the car?... and pressure differental? whats that and how to fix

jhammons01

bench blled won't do you any good now, It is when you attach tubes to the MC and use something to plung the MC. You bend the tubes up and back into the res. The fliud is supposed to just circulate as you pump the MC with a screwdriver or something. Now that the MC is allready on the car and you pushed the air down the tubes it would be useless to do it now.

You say you gravity bleed the system and then you force bleed it 2-3 times (???)

First, the two rears have two bleeder valves one on top and one in the back. Bleed the lower one first. Start in the RR, then LR then FR, then FL, (start as far away as possible) use the rubber hose and the coke bottle. Now imagine forcing a bubble through the lines all the way from the front to the back......2-3 pumps aint gonna be close. Try 10-20 pumps and you know that there is air in the system cause you broke the system open when you put the MC on there. The hose and coke bottle is so that the end of the hose in down in the fluid of the bottle, when you SEE bubbles coming out then you know that you have forced that air out of the system. Move to the next.....don't get stingy with the brake fluid....it's cheap. And think that while your doing this you're cleaning all that 14 year old fluid out. You can claim that you "flushed" the entire brake system on your list of Mods.

The pedal will not get firm until you have completley bleed the very last caliper which should be the Left Front.

That Whoosh sound will now be gone.

nyc_scorpio

iTrader: (1)

well i had the same problem, and the woosh sound is the small 1 way valve thats inside the small hose that connects from the master to the fitting on the firewall. i changed that valve that was not holding its 1 way pressure, and wala. it was all good again.

StarScreaM2k1

Oh? where did u get that pipe/valve from? Mazda directly? and do you have a part number so i can go buy it? Sounds like that may help...

this braking this is stopping me from getting the car certified to drive. So please any help is appreciated! i know theres some guru's here...

NOPR

same exact thing happened to me, turned out it was the brake booster. take off the master cylinder (you're going to have to anyway most likely) and look at the prong coming out of the brake booster. it shouldnt be able to move freely left and right or up and down, only in and out. Mine was wobbling around like crazy and when i pushed the brakes i could see and hear that that was where the air was coming out. The seal around the prong was completely dead. So i bought a new brake booster but the bolts dont fit and thats whole new slew of problems and a different, long story. This is a problem im still working with but im positive my brake booster was screwed and that was what caused the really slow blow-off valve type noise. i would try what nyc scorpio said first, but also inspect the brake booster and see if you can locate exactly where the air is coming out.

jhammons01

Really??

Maybe it is a whoosh of air versus, Air bubbles that i was thinking.

The Gurus' have spoken, I have to leave Tribal council immediatley
*brings torch and it gets extinguished*

*John Pays 100 forum bux to stay in game and returns with lit torch*

StarScreaM2k1

could it be the brake booster? or the proportioning valve?

StarScreaM2k1

any other idea's anyone?! seems like this problem is a doozy

MidnightOwl

This happened to me, same EXACT deal. I rebuilt the master cylinder, only to have the damn thing go nuts again. It turned out that right rear caliper developed a leak where the e-brake meets the caliper and I had to replace the whole thing. It wouldn't leave a puddle of fluid, but it would drain almost the entire reservoir in a day just from driving around.