ApexAndy

My car is an 88' GXL with no ABS (has the AAS). When my brake master cylinder went, I got an exact replacement; problem was the previous owner did some wrenching. So the replacement part has a thread slot for the brake fluid pressure sensor, yet my old master cylinder does not have the sensor.

What I plan on doing is putting in a turbo BMC since it is (as per previous posts) a heavy duty unit that matches the 4 piston calipers. Would this work or would they not match up? I'm appreciative of any knowledgeable input.

misterstyx69

iTrader: (142)

there are different types of Brake masters.I had 3 different ones at one point..Two had the sensor and one did not...I have run the 4 lug Master on the TII brakes,with no problems...you are going to find that the Masters have different Places where the Front caliper Lines go..Like one to the Front,and also one to the Proportioning valve,ETC..so,In short,you can run the Master..it's the Booster,actually Which is Bigger from 4-5 lug brakes..they are However the Same in size,between 5 lug N/A to that of a 5 lug TII....The Vacuum pipe on the TII booster is about an inch and a half and Straight.But the Vacuum pipe on the N/A booster is Curved up a bit,to go onto the Steel line along the Firewall..anyhow,I hope that Sort of Explains stuff,and helps you a bit..OH>>If you use the 5 lug booster,the Vacuum Hose that connects to it has a CHECK valev in it..so make sure that hose is On correctly or you get Hard brakes(Hard pedal,no real power to the brakes,feels like a brick wall)..If You run the TII booster you are going to have to find the Vacuum hose set-up for it..as they are slightly different on TII's as opposed to N/A's..Suggestion,take a look at the Parts manual.(can be found online)..and compare all the parts that you need,as to what you actually Have.

ApexAndy

You've been alot of help misterstyx69. New idea: I have the old brake master and I also have a new one. The old one is bad, yet the new one has the thread for the brake pressure sensor (thus both are bad). I was thinking of swapping the guts of the new one into the body of the old one. Would this work? (BTW, I did assume before that the GXL 5 lug brakes were the same as TII brakes)
Also, if this is possible should I be aware of any tips when working on BMC as well as any special tools. Any knowledgeable information is appreciated.

One more thing, how the hell do I remove the damn brake reservoir? I went gorilla torque on the old one (which is how it advises to remove it in the Chilton's book) and broke one of the legs, and I don't want to do the same thing again.

misterstyx69

iTrader: (142)

ya..you can transfer the guts,but that would be kind of Counter-productive..Taking a NEW one and tearing it apart,and putting it into a old Casing..tell you what..send me PICS,(misterstxy69@hotmail.com Of both of them)..The Reservoir is a bitch to get off,and takes Finesse and Patience..the Best way I found to put it in though is a little vaseline and heating the Areas with a Torch(SLIGHTLY)..the part will slip right on.with a Good Press down.,And as far as the sensor,it Tells you that the Pressure is Down or the fluid is low,which you Would Notice anyways,IF you Know the Feel of the brakes at their Potential..so you can just disconnect the Sensor at the Plug On the Harness...Oh post Once more..that way you can NOW PM anybody,since you need 15 posts to do that!

ApexAndy

Here goes post 15.

My logic behind swapping the "guts" was that the manuals show the insides as being nothing more than springs and some o-rings. If this is correct, then the initial failure would have been with the o-rings sealing, thus swapping new ones in would fix it. My concern would be if the internal clearance would allow this.

I doubt the casing has a problem with it (though I'm not sure exactly how I would be able to tell besides a leak, of which there is none).

Also, I'm hoping hot water will do to remove the reservior.

SpooledupRacing

I believe they are different internally too...

boostedfc3s

iTrader: (2)

If you know exactly what BMC was on the car that failed, you could get an overhaul kit along with the correct size hone. That way you know that you have the corrects guts inside it with a fresh surface inside the housing.

SpooledupRacing

or just buy a new brake master cylinder for the car you are putting it on

ApexAndy

Well, I'm not sure which BMC was originally in the car. I am assuming a turbo model since a weaker single piston model would not have worked as well in the car. So, if the casing (which worked in the past) is satisfactory, and the internals of GXL (AAS models with 4 piston) and turbos are the same, then it should theoretically work.

I swapped the internals out already (hot water and vasolene). Tonight I'm bleeding the system (Racing blue brake fluid, let me know what you've heard). I'll keep you posted in case any poor soul in the future has my luck.

And thanks alot for your input and advice. Good to see you're as enthusiastic about the RX-7 community as rotaries themselves.

ApexAndy

OK, so I installed the "new" brake master cylinder, and the pads and lines were replaced last week. Through the bleeding process (done in the right order) it was downright beautiful when as the last wheel was done it was very stiff and progressive.

Turn on the car and the brakes act a little odd. They initially dive to the floor, then as you continue to pump it gets pressure and gets firm. Lay off it for a while, and the same happens. What should I do/check?

Also, there was no air as I was bleeding and I ensured all the old stuff came out. The lines are secured. I assume that this is the same thing as when I changed the clutch master when I had to continue to pump till the pedal got firm enough. I'm highly appreciative of any info at this point. Thanks.

ApexAndy

weekend bump, Give me some advice

misterstyx69

iTrader: (142)

you got air in the lines Andy.Start Bleeding the Brakes from the Furthest Caliper from the Master..then proceed to go to the Closer one,and so on..Look up RX7Doctors thread of Bleeding the Brakes.It Definitely Sounds like Air is in the Lines..Another Thing that you can do Is Try a One man Brake bleeder Kit,or have a friend to Pump,pump,pump..while you Crack the Bleeders,One at a time.Another Suggestion is to Crack the Rear bleeders,and while you have the Master Full,and let the Fluid,Gravity bleed out..it will Pour out(sort of)the bleeders.Then you can start the Bleeding the rear passenger,rear Drivers.then Do the OPEN bleeder thing with the Front...anyhow,that is some suggestions.

ApexAndy

ok, thanks mistery. I was so sure i did it right, since there was absolutely no air in the lines when i bled it (in that order). Would speedbleeders work?