yup mine was actually worse.. i would fill my MC with fluid and by nightfall it would be empty, the rear seal was bad on the piston so everything would leak down and inside and out the vacuum booster. i replaced the master cylinder and no leaks fluid stays where it's meant to be

another tip to diagnosing this is to look at the separated reservoir from the side of it, its separated kinda like a clear cigarette lighter whichever side doesn't have fluid in it has the bad seal but if you have bad break lines then all fluid most likely will escape both of them

 

Well I just got my car back from my local rotary shop and unfortunately not much has changed. Here are some pictures of the install and a shot of leakage under the car which I thought was caused by cracked rubber brake lines.


rags and paper towels as well as caps over the brake lines are needed


out with the old...


it was leaking at the seal in between the part and the power assist unit


you can see the bottle i used to bleed the system per fsm instructions...


in the with the new.. (if you look closely under the vacuum hose to the booster, FA18 is engraved on the MC so this is for GSL with rear disc brakes)


two clean reservoirs...


here is a shot of where brake fluid collected. i highly doubt its a fuel line that was leaking.

SO I replaced my rubber brake lines with stainless steel ones (Earl's brand) sold by Racing Beat. I haven't looked at my old lines yet but they told me none were leaking... Hm... did I just spend 100 dollars for nothing? I mean my old lines were dry but with my old leaky MC I didnt have a problem, just the annoying leak. It appears that the spot of where the fluid collected is nowhere near the rubber lines on the calipers. Maybe this was just old fluid still slowly leaking down from before (the new MC doesnt leak).

Perhaps its one of the hard lines that deliver the brake fluid to the rear? I think it runs next to the hard line for fuel and fuel return? Still seems moist underneath but I didn't see any droplets formating. I gotta wipe that area clean and look for kinks or cracks for leaks. But then wouldn't this pull air into the system? I don't know I just know I don't have money to replace everything with new OEM parts because it's making me go broke!

SO I am going to return my 'new' MC because I've been suggested that even after adjusting the brake pedal rod my brake pedal still sinks to the floor. The braking feels better with the new lines and re-bleeding but just barely. So I also suspect it is a defective MC.


at least I haven't repainted my car yet..

Thanks for reading if you made it this far... /end rant lol

 

yes mine looked exactly the same like i said the rear seal was shot so it would leak down the vacuum booster and into it which can ruin the diaphragm in side it. if that was ruined that would make a difference in the break pedal but not how your explaining. if u still have a pedal drop then your loosing pressure from somewhere. to see if it's a defective MC open the cap on the reservoir and have someone pump the pedal, if u see bubbles and moving fluid in the upward direction then your front seal inside is bad. my friend bought a clutch master cylinder for his Datsun 280zx and this had occurred so its very possible and your brake pedal rod shouldn't have any effect on brake pedal drop the hydraulic system should hold pressure at any input, the brake fluid on the bottom of your frame is as mine looked i noticed mine when bleeding with the bad master cylinder it was dripping down because of the rear seal. good luck with it check all brake components throughly master cylinder seals, lines, calipers maybe even check out the diverter that splits the pressure by the MC make sure all are in proper operation and brake pedal drop shouldn't occur oh yea and don't return the new MC because it just gonna keep leaking into your brake booster having that new is a key step to fixing this problem, if it is defected then just have them replace it, i strongly suggest keeping it its only 50 dollars and saves alot of headaches

 

Thank you for your input my84gslrx but I haven't seen any decrease in fluid in the reservoir so I think my new MC is not leaking. Probably a hard line underneath.

So before I decided to call the company where I ordered my BMC I decided to try one more thing, bench bleed it properly which I made the biggest mistake to not do in the very first place.

Lo and behold, I have brakes again!

OK now I am thinking...,

Did I just get ripped off a couple hundred dollars (yea, the mechanic charges pretty high labor rates) for stainless steel lines and installing that plus bleeding brakes again which was all done at the shop. Oh, and also adjustment on my brake pedal piston which was way out of spec and I got charged for that without prior consent either.

Like I said in my previous post, my car was released from his shop with very little to no difference in pedal brake feel at all.

He even told me he had a hunch it was BMC. Well why didn't he touch it without my consent (jokingly)? Why didn't he offer to order a replacement and install that for me? Instead I had to pay for my wrong diagnosis and he didn't even suggest other possibilities before hand. I admit I told him to replace unknowingly unnecessary parts.


This is the first time I touched any of the brake hydraulics and learned a lot from doing it myself. Now I am confident (and motivated knowing how much it will cost me at a shop) to do brakes myself. I know its one of those maintainance everyone should know like changing the oil and filter. But I just spent like half an hour bench bleeding it and it solved my problem.

BTW the droplets of brake fluid (I believe to be) still collects at that spot on the frame. I still have to check the hardlines underneath. I thought it were the old cracked rubber brake hoses but obviously it isn't.

But anyways.... did I get treated unfairly? I did most of all the work bleeding it twice and installing the new MC before the mechanic just bled once and installed new lines and adjusted the brake pedal rod (I think I said piston above.. so perhaps it was inside the car instead of at the booster I'm not sure). I don't think I can get any money back but was it wrong of the mechanic to tell me after all the work was done and still barely any improvement was felt, that the MC was defective/ the problem lied in the MC but didn't even try to touch it? (obviously)

P.S. I'm not sure if he reads this forum or not but I don't think he will be seeing my car at his shop for a while because of this past experience.

 

Both my parts car and my old seven had the same build up on the brake booster to MC like in the picture, but the old seven had no problems braking or leaking oil...

 

yes, no problems braking before for me. but, it did leak which annoyed me to keep refilling it and it leaked down the side of the booster hence the paint gone and also down to the bottom of the car.

So I bled all four calipers starting from the farthest working my way to the closest to the bmc. Did see air bubbles but just a few. When I got to the last one, air bubbles just kept coming forever! Still after bleeding it a LOT in the drivers front side, I turn on the car and it feels great! Then I release the parking brake and it feels like how it felt after I bench bled the MC earlier today. I did have the e-brake down when bleeding the rears though. Looks like I'll have to try the MC again tonight since my 30 days to return it is coming up.

BTW does anybody know if brake fluid has any effect on tires? Some got on it.. well I guess a lot on one side in the tread. Does it mess up rubber?

 

So I just finished giving the BMC another shot... I bench bled it again with the rubber brake hoses feeding into a jar of brake fluid and took off the front drivers wheel and let the bleeder valve open since thats where the bottom hard line goes from the MC.

Then I bled all four corners again with the e-brake down and the moment of truth... same pedal feeling..

Of course when the engine is off there is pressure but once the engine is turned on the pedal sinks down. Not as much as the very first time I installed the MC but still sinks down. If I pump it quickly pressure does build up but then it slowly sinks down again. When I just press the pedal without pumping it, there is about 1.5-2 inches of "air" before it gets hard and thats usually when I plunge forward in my seatbelt because the brakes suddenly kick in when I'm slowing down/stopping.

I think I tried about everything. Bench bled and bled the entire system twice today. Second time bleeding produced very few air bubbles and some spurts of teeny tiny bubbles.

I'm gonna call up the place where I got this part and return it. It was only $44.96 too! What a deal considering Black Dragon sells it for $80 and Mazdatrix sells it for $120 or so. Oh well I got what I paid for and now I'm gonna have to pick one of those companies or try my local auto parts store because I do not think the company I bought the part for has them anymore since I probably got the last one left. Hm I wonder if BMC that have been sitting for a while usually have problems like mine since well there hasn't been any fluid through it for a long time.

 

IF you have really firm functional pedal feel and no sinking with the engine off, but problems when the engine is on, the problem cannot be in your MC. Nothing with the MC changes depeding in on the engine running. That's why we bleed brakes with the engine off.

I'm not sure what exactly is going on here, but I'm suspicious of your booster, if the probelm revolves around the engine running or not.

If you can get a good clean bleed & that gets you a solid pedal feel that actually stops the wheels engine-off, then the MC is fine.

Can you discribe the method you are using to bleed your wheel cylinders?

 

I'm doing the traditional air bleeding method. Got my lil bro to pump the pedal 5 times hold and I loosen the bleeder screw to bleed the fluid through a nylon hose submerged in a jar of brake fluid until no more bubbles appear per FSM instructions. I bleed each caliper at least 6 times or sometimes like mad until no more little bubbles show starting from the RR, LR, RF, the LF which is working my way from farthest to closest to the MC.

Of course I bleed my MC before bleeding at the wheels.

Since I didnt have the bleeder kit along with my MC I used my old rubber brake hoses which screw right on to the output holes in the MC. I bench bled it in the car which was kind of a bitch because I tried attaching the hose to the bottom hole but theres barely any room. So I just attached a hose submerged in brake fluid to my LF bleeder screw and opened the screw since this line is connected directly to the bottom port. The other two ports on the side I submerged those in a jar of brake fluid also rather than routing it back into the MC because the female ends of the hose cannot both fit at the same time in the reservoir. I bled the MC until only a stream of brake fluid came out and no bubbles seen coming out of any of the ports.

Well I'm ordering from a reliable place, Mazdatrix which I should've done in the first place. I was trying to save a couple bucks by finding the cheapest new MC and I didn't want a reman. (I'm sure there would be nothing wrong with it either and it is a lot cheaper) and I ordered from unheard of places that probably had the part sitting for years. Trying to save a couple bucks cost me a bunch more money that wasn't even close to what I tried to save. Well now that I did all the work myself minus new (yet, unneeded) SS brake lines I am definitely motivated (and confident) to do it again and save myself the charge of labor and its so basic and easy.

I should have my new MC from Mazdatrix in 2 days. I forgot to ask if it is a Mazda part but I am assuming it is because of the OEM part number and not another competitors part number.

 

well sorry to hear it didn't work out for u, my car had the same exact problem i bought the thing with no brake fluid in it and no pedal what so ever, i figured it had a problem, so i put in fluid and bled all the wheels and i had a pedal. while i was bleeding the driver wheel i saw something dripping which i thought was melting snow but i remembered that i had it in my garage for 2 days so i smelt the fluid and sure enough it was brake fluid, that night i checked the fluid and it was as i illustrated in the picture above and i took a tech class on automotive technology last year in school so i knew where my problem was originating from once i saw the brake fluid on the brake booster. so i bought the new master cylinder and i bench bled mine in a vice with the kit it came with, after that i put it on the car but i had no pedal again because i let to much air in in the transfer. i bled them like 15 times each wheel and have a spectacular pedal with the engine off, unfortunately i haven't been able to start my car because i sent my carb out to get rebuilt all the way in California bout a week and a half ago and i am impatiently waiting for a return email or call as I've been trying to reach the guy but am, getting kinda skeptical weather i getting it back or not anyway, no leaks or pressure drop for me, if your break booster was shot it wouldn't make your pedal drop to the floor unless it was really pulling and assisting your brake pedal rod movement a lot and even then u wouldn't start rolling after it was to the floor because your hydraulic system should hold pressure no matter what. if your diaphragm was bad u would hear it in the car, also u would have a harder to operate brake pedal, so idk if u checked the front seal or not in the old one by opening the cap and hitting the pedal but since its to late, if u install the master cylinder correctly and no components in your hydraulic system are leaking then u should have brakes regardless of the vacuum booster. and also take into account obviously if u start rolling at a light then your brake clamping force is stopped by hydraulic pressure shortage to the calipers, and lets say u have a bad caliper, unless all four are bad, u shouldn't start rolling because at least one caliper can hold u at a stoplight for sure, so your only place to track would be the lines which are easy to see if u hop under and check for leaks or the master cylinder, now pumping the pedal with the car off isn't putting anywhere near enough pressure as it running on the master cylinder so if its fine when your off then u start it and it sinks its probably the master cylinder not holding up to the high pressures while on but can tolerate just your leg muscle when off, this is from what my understanding of the hydraulic brake system is if anyone see's anything wrong with my statements feel free to help this poor guy out lol. hope that helps

 

heres a pic just to help ya out, im tryin all here, and if it dosent work then from what your saying about u hit the pedal then a second later it stops hard, its probably rusted and worn out brake booster and pedal link

 

Thanks for your time to write your previous posts and draw a diagram to bench bleed the brakes. I will try bench bleeding it out of the car with my new one which I hope will arrive tomorrow or Friday. I'll keep yall updated if it works or not.

Another thing I forgot to add was that I bled the system with the e-brake down the whole time because with the e-brake up it restricts the rear calipers from full movement and you can feel the difference in the pedal too.

 

its no problem man that y i joined this cuz i just got my rx and hope to get the same in return, yea sounds about right to me, only sometimes the parking brake is only one wheel

 

[PART 1]

Let me guide you through my pictures...


So the left box is the first MC I ordered. Middle is from Mazdatrix. Turns out its not a Mazda part but made by PBR which I seen online for a cheaper price, so I paid more than retail (which I should've expected from Mazdatrix). At least theyre reliable with shipping. The right is my old MC.



First I sucked out as much of the brake fluid out of the reservoir by first removing the float sensor and using the tube to bleed my brakes connected to a syringe. Then I removed it and capped the hard lines with the rubber caps supplied with the new MC.


Here is a picture of all three MC for comparison. Left is the old MC, center is the defective MC and right is the PBR MC. Notice PBR does not supply the sensor.


Bottom view of the old MC.


Bottom view of the defective MC.


Bottom view of PBR MC. Notice that PBR does not have the same stamping as the first two. Perhaps the first two were Mazda parts or from the same manufacturer.


Old MC has a FA18 stamp and a letter on the bottom. I think it's an M.


Defective MC has FA18 also stamped with the letter E and Q on the bottom.


PBR stamps.


13/16" stamp on old MC.


Defective unit.

 

[PART 2]


Nothing on PBR.


Two same style caps... you guessed it for the old and the defective. Different for the PBR. Cap is the same but the second piece is all rubber so its a cover plus gasket at the same time.


Ready for priming using my old rubber brake hoses submerged in jars of brake fluid. The bottom port didn't really put much fluid but the two side ports put a lot of fluid.

So I bled the system twice at all four corners. I definitely can feel the difference of SS brake lines but I still feel I have air in my system so I will bleed the MC again and then bleed the system again. But there is an improvement with the PBR MC compared to the first replacement I bought. The pedal still somewhat sinks too far down for my liking. And also it holds pressure with the engine on but sometimes it just sinks down so it's kinda random when it has a firm feel and other times it feels like there is some air. I am not sure if the mechanic adjusting my pedal rod affected the play. But the car definitely stops more predictably and faster. I'll give another update after I bleed the entire hydraulics yet again.

I forgot to take a picture but in the very first picture on part 1's post there is a nut on one of the side ports and the other two do not have that.

 

That's my setup to bench bleeding in the car. Two hoses connected to the side submerged in a jar of brake fluid. Bench bled for the second time and then connected back the two hard brake lines. I figure that I didn't need to open up the bottom port because thats directly hooked up to the LF caliper so I'd just be bleeding it later.

Then I proceeded to bleeding the entire system starting from the farthest of the MC working my way to the LF (closest). I did notice more air bubbles coming out and then very very tiny bubbles that look like dust and they seem to be generated by the spurt of fluid coming out when I open the bleeder. So I turned on my engine and it still didn't feel right and I realized that my e-brake was up the whole time so I re-bled the system again with the e-brake down. I also used my palm to bang the calipers and MC along the way to shake loose any air bubbles clinging on the inside surface and did notice a few more bubbles through the air bleeding process. The feel of the pedal did not really change much even after the forth system bleed on this new MC.

I made sure everything was tight and fluid filled and went for a drive. When I jab on the pedal fast I feel pressure and then it slowly sinks until it gets to one spot (not all the way down of course) which is very firm. When I am gently applying the brakes, the car slows down normally as it should but the pedal feels like I'm just pushing on air, until I get to the one point and it is very firm. I can even lock up my rear tires if I wanted to. The brake action is very fast though if I want it to be. Again, it's just that when I gently apply the brake it feels from very spongy to no resistance, then very firm at that one spot. When I jab on the brake quickly and hard, I can feel resistance but then it slowly sinks to that one spot (which then stops the car very quickly because the pedal feels very firm).

It didn't feel that firm (I'm talkin about that spot where the pedal reaches to) before when I had my stock hoses so I'm guessing this is the feel of the new SS hoses. But it's just that my brake pedal doesn't feel consistent as mentioned above.

Do I still have air in my system?

I might just take it to Wheel Works to have them look at my pedal feel. Maybe pedal feel is different now because the mechanic adjusted my brake pedal rod. I think it is the one on the inside of the car (which I didn't even touch ever before) and not the rod on the booster. So maybe it needs to be adjusted back to before. This is just another thought.

 

Nice thread. This car has drums in the back right? Have you replaced the seals back there on the pistons?

 

No I have a GSL with discs in the rear hence me ordering the FA18 part number rather than the FA07. But I believe the only difference according to Kentetsu is that the drums MC just have a check valve in them.

Now after reading through many threads with the same symptoms I'm having, could it be that I have another faulty MC with an internal leak?

I believe that my booster (power assist) is working because when I turn on the engine the pedal sinks/fade down whereas when my engine is off the pedal pressure is firm. Then another thing I read in a thread about brake fluid leaking into the brake power unit which can cause a crappy idle when you hit the brakes which sometimes happen to me but usually when the car is warming up. My old one obviously leaked at the rear seal but I don't think the diaphragm inside was damaged since my booster still works.

Since I bench bled the MC twice and all four calipers four times already today err technically yesterday and still no difference, and since I do not see any seepage around the calipers or brake lines. I'll probably have my MC checked later.

Yes, no food and no sleep for the love of my Seven and of course, because I want everything to be working properly or better than new

 

Lots of reading, lol. Fwiw, on the PBR MC, that odd looking fitting in the rear port is a repair for stripped threads on reman MCs. It's not a new unit.

I used to bench bleed, found it too messy and kept dribbling fluid on the paint during the install, along with loosing enough fluid that air got back into the system. All the MC really needs is a good prime, but I must say, you got very creative with your effort.

Before you started the bench bleed, you could have swapped the reservoir for one with a sensor. I find it odd that the push rod needed any adjustment. With a new master, it shouldn't need it with the close tolerances between different MCs.

Since you have been unsuccessful with 2 new/reman units, the fault may lie in your bleeding proceedure. Either you're somehow allowing air to re-enter the system, reservoir level drops to low, a caliper is leaking or a line fitting isn't tight.

 

Thanks for reading trochoid. I want to be as clear as possible so that others who read it when they have problems can pinpoint it down to the problem when they have troubles and solution when I solve mine.

Great so Mazdatrix sends me or orders reman units and also sells them for a new MC price. As long as everything works in the end I'll stop feeling like I was ripped off.

Also I took off the sensor on my old unit and slipped it on my 'new' PBR reservoir. And I do not believe the push rod on the booster was adjusted but the rod inside the car on the brake pedal was by the mechanic for whatever reason I do not know since I did not have trouble with the pedal pressure before (just a leaky MC!).

I think you're right about my bleeding. I think I am bench bleeding the MC wrong (creatively at that). First I do not believe the MC is level when I bench bled it and also I did not and can not pinch the hoses when the piston returns to its neutral position. But I do not believe the latter should matter because all the hoses were submerged in brake fluid which should prevent the air entering the system.

I always check my reservoir level and that all the fittings are tight. I should try using teflon tape on the threads so air does not enter through the threads but I think the air entering through the threads are very minuscule.

 

Teflon tape... If you're talking about on the brakeline fittings, that's not needed or helpful. The nut threads on flared tubing connections don't have anything to do with maintaining the seal; sealing is between the flare and the seat. The nut just provides pressure on the flare.

If you're talking about using it on the bleed screws, it might help some if you were vacuum bleeding, but if you are two-man bleeding and the bleeder is only opened when there's pressure on the line, there's no way air can enter anyway.

Two bad replacement MC's from 2 different sources would be very much against the odds. Not impossible, but really, really unlikely.

 

Well folks I just got back from taking my car to Wheel Works (additional $75 primo price to spoil my 7) and they just flushed my hydraulics twice using a vacuum to suck out the fluid and had another reservoir to keep my BMC reservoir full. They said they pulled some air out but suggest looking to replace my booster. The symptoms unfortunately still remain unchanged. So this means my manual pedal bleeding was successful and my bench bleeding as well but of course a vacuum would pull out all the air or whatever was remaining in my case.

The car stops quickly, even more so with the stainless steel lines installed but it's my pedal feel I am still not satisfied about. As I said same symptoms as described in post #41. Also I don't think I mentioned this but when I keep pumping the pedal with the engine on I notice that the idle stumbles or hunts. This is more apparent when the engine is cold and warming up rather than a fully warmed up engine idling. Signs of booster failing? I should probably ask the mechanic that adjusted the pedal rod to know exactly what he adjusted and then go to the booster from there.

Here is my setup on my system: new SS lines, new/rebuilt MC, brake fluid flushed completely numerous times, calipers were working before and still work.. is there anything else that touches hydraulics

hmm.. I don't think so. So either the pedal rod I need to look at or booster. OR could it be that my master is still bad like my first replacement?

 

 

If my booster is leaking vacuum probably since when I pump the pedal fast some pressure builds but then it sinks down to that one spot of firmness. So that would mean that my first MC was NOT defective at all then. If I swap that back in exchange for the PBR and return the PBR back to Mazdatrix then I would have to bleed the system which I do not want to do since I just spent more money for that. I guess I'll just have to bite the difference (about $100 off the top of my head) to keep the PBR and return my first MC I bought that I claimed defective. Gosh maybe it could be my booster thats failing because in my very first post #18 I mentioned the sound of air leaking when I first took off my old MC but do not recall of this taking off my first replacement MC.

If anybody is curious.. I have spent about $350 for SS lines and install, labor to bleed and adjust pedal rod, about $150 shipped for the reman (ridiculous since remans should be around $30) PBR from Mazdatrix, about $75 for vacuum bleeding, about $15 for my own brake fluids sooo that's almost $600 total for my brake hydraulics alone! Whoa... and my "problem" is still not solved. Flame away if you wish I'd say I'm pretty idiotic for spending that much for just brake hydraulics but I definitely learned a lot about the hydraulics.

 

Wow that is some serious money for brakes. But now you can fix the brakes on other cars as well.